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Leaf Form and Photosynthesis
Do leaf structure and orientation interact to regulate internal
light
and carbon dioxide?
William K. Smith, Thomas C. Vogelmann, Evan H. DeLucia,
David T. Bell, and Kelly A. Shepherd
M orphological and anatomi-
cal features of plant leaves
are commonly associated
with metabolic type (e.g., Kranz
anatomy of C4 species), amount of
sun exposure (e.g., sun and shade
leaves), or water stress (e.g., xero-
morphism). However, although the
primary function of the leaf is to
absorb and process sunlight and car-
bon dioxide for photosynthesis, few

structural features of leaves have been
related mechanistically to these tasks.
For example, it has been known for
over a century that the internal
anatomy of leaves is characterized
by different cell layers (e.g., the pali-
sade and spongy mesophyll) and that
stomatal pores can be located on one
or both sides of a leaf. Yet, only re-
cently has any functional relationship
between leaf form and photosynthetic
performance been suggested.
A variety of ecological studies have
correlated numerous leaf structural
parameters with photosynthetic per-
formance (e.g., Abrams and Kubiske
1990, 1994, Hinckley et al. 1989,
William K. Smith (e-mail: [email protected]
edu) and Thomas C. Vogelmann (e-mail:
[email protected]) are professors in the
Department of Botany, University of Wyo-
ming, Laramie, WY 82071-3165. Evan H.
DeLucia (e-mail: [email protected]) is an
associate professor in the Department of
Plant Biology, University of Illinois, Ur-
bana, IL 61801. David T. Bell (e-mail:
[email protected]) is an associate
professor and Kelly A. Shepherd is a re-
search assistant in the Department of
Botany, The University of Western Austra-
lia, Nedlands, WA 6907 Australia. ? 1997
American Institute of Biological Sciences.
Terrestrial plants

responded to the
amount of sunlight
and stress in a given
habitat by evolving
leaf structural
properties in concert
with leaf orientational
capabilities
Koike 1988, Reich et al. 1991, Walter
1973), but mechanistic evidence
pointing to a complex influence of
leaf structure on photosynthesis has
been obtained only recently (Tera-
shima and Hikosaka 1995, Vogel-
mann et al. 1996a). A comprehen-
sive synthesis of the functional
significance of leaf structure, as re-
lated to photosynthesis, has yet to be
proposed. In addition, no studies
have associated leaf structural char-
acteristics with differences in leaf
orientation relative to the Sun, de-
spite the recognition that both
structure and orientation can have
dominant influences on whole-leaf
photosynthesis.
In this article, we present a syn-
thesis of current findings in ecology,
physiology, and biochemistry that
points to a fundamental relationship
between the evolution of leaf form

(structure and orientation) and pho-
tosynthetic performance. This rela-
tionship includes a strong coupling
between leaf structure and orienta-
tion that is not documented in the
literature and that has not been at-
tributed to photosynthetic function.
We describe field observations of
correlations among leaf structural
symmetry, leaf orientation, and the
resulting amount of incident sun-
light on both leaf surfaces. We also
summarize physiological and bio-
physical evidence of the impact of
this structural symmetry on the cap-
ture and processing of sunlight and
carbon dioxide for photosynthesis.
We propose that the evolution of
leaf structural symmetry is based on
leaf orientation and the regulation
of incident sunlight and is driven by
a common functional theme-maxi-
mizing photosynthesis per unit leaf
biomass by regulating light and car-
bon dioxide gradients inside the leaf.
Although differences in chloroplast
abundance, physiology, and behav-
ior at different locations across the
mesophyll are also important to this
central theme (e.g., Evans 1996,
Terashima 1992, Terashima and
Hikosaka 1995), these topics are not
emphasized.
For a typical plant leaf, sunlight is

incident on the upward-facing
(adaxial) side, whereas carbon diox-
ide uptake occurs predominately at
the lower (abaxial) side, where most,
if not all, of the leaf stomatal pores
are found (Figure 1; Meidner and
Mansfield 1986). Thus, whereas
chloroplasts just beneath the upper
epidermis of this leaf should experi-
ence the highest light regimes, the
December 1997 785
Figure 1. A cross-sec- Incident sunlight
tion of a typical leaf
showing the opposing U er
gradients of internal epidermis ? O?
light and carbon diox- uepidermisal ide when sunlight is in- '
CO?i
cident on the upper leaf
surface and stomata are o
present predominantly i 5 ) % on the lower surface.
Two pairs of hypotheti- pongy
cal curves are drawn: Lower c.
one pair (dashed lines) epidermis Stomata
shows strong gradients Photosynthetic
that generate a narrow
zone of overlap (indi-
cated by small bracket) between high light and carbon dioxide,
and another pair (solid
lines) shows smaller gradients that generate a broader zone of
overlap (large bracket)
between high light and carbon dioxide. A broader zone of
overlap would generate

greater photosynthesis per unit leaf biomass, which may be a
fundamental driving force
in the evolution of leaf form (i.e., structure and orientation).
carbon dioxide concentration is high-
est on the opposite side of the leaf,
next to the lower epidermis. Steep,
opposing gradients in light and in
carbon dioxide would not seem to be
optimal for maximizing photosyn-
thetic efficiency across the entire
thickness of the leaf (Figure 1). It
seems logical that leaf form would
have evolved so as to maximize photo-
synthesis per unit leaf biomass in the
face of these opposing internal gradi-
ents of light and carbon dioxide.
Does leaf structure regulate
internal light?
Considerable evidence indicates that
the structural properties of leaves
(apart from changes in chloroplasts)
may influence photosynthetic per-
formance. Most of this evidence
comes from observations (Terashima
and Hikosaka 1995) that the shape
of the light-response curve of photo-
synthesis (i.e., the amount of carbon
fixed per amount of light) can be
altered by changing the angle of inci-
dence of direct-beam light, the direc-
tional composition of the incident
light (i.e., whether the beam is dif-
fuse or direct), and the type of leaf
structure (i.e., whether it is asym-

metric or symmetric). Experimen-
tally disrupting the parallel rays of
direct-beam light by using a light
diffuser caused substantial alter-
ations in the light response of photo-
synthesis (DeLucia et al. 1991,
Terashima 1989). Similar alterations
in photosynthesis have been observed
when structurally asymmetric leaves,
which naturally intercept direct sun-
light only on one surface, are illumi-
nated on the opposite side instead
(e.g., Evans et al. 1993, Kirschbaum
1987, Poulson and DeLucia 1993,
Terashima 1989).
Increasing evidence implicates the
leaf surface and all of the major cell
types within a leaf (i.e., epidermis,
palisade, and spongy mesophyll) as
influencing the capture and internal
processing of absorbed sunlight
(Vogelmann et al. 1996a). Moreover,
orientational and corresponding
structural effects may have strong
influences on photosynthetic prop-
erties. Chloroplast acclimation to
altered light regimes appears unable
to compensate entirely for alterations
in natural light regimes or normal
leaf optical properties.
Upper epidermis. Leaf surface struc-
tures, such as epicuticular waxes and
epidermal hairs, have been reported

to affect whole-leaf photosynthesis
due to alterations in absorbed sun-
light. For example, high solar reflec-
tance from pubescent leaves of desert
broad-leaf species results in optimal
leaf temperatures, reduced transpi-
ration, and enhanced photosynthe-
sis (Ehleringer and Werk 1986,
Johnson 1975, Smith 1978). Also,
the hydrophobic nature of leaf pu-
bescence found in numerous species
may prevent a water film from form-
ing during dew and rainfall, a poten-
tially large barrier to photosynthetic
carbon dioxide exchange (Brewer and
Smith 1994, 1997, Smith and
McClean 1989). However, this same
water repulsion may also create a
monolayer of small water droplets
over the entire leaf surface. Because
of the lensing effects of these water
droplets, a highly variable sunlight
pattern develops over the leaf sur-
face, ranging from full shade to over
20 times full sun at focal points be-
neath individual droplets (Brewer et
al. 1991). In most species tested, a
layer of leaf trichomes holds the dew
droplets above the leaf surface, well
beyond their focal distances, greatly
reducing the potential damage of this
focused sunlight to the photosyn-
thetic system.
Another common feature of the

leaf epidermis is their lens-like cells,
which were originally thought to be
involved in orienting the leaf toward
the sun (Haberlandt 1914). More
recently, however, it has become clear
that these lens-like epidermal cells
both collect and focus incident light
into the leaf interior, possibly to en-
hance photosynthesis (Bone et al. 1985,
Lee 1986, Poulson and DeLucia 1993,
Poulson and Vogelmann 1990). These
findings also show that the geometry
of individual epidermal cells may
vary according to sunlight exposure.
Spherical epidermal cells may be
more beneficial in shaded environ-
ments, adding a much greater ab-
sorbing area, not only for the pre-
dominant levels of less intense diffuse
light, but also for the direct sunlight
(sunflecks) that penetrate the canopy
at low angles of incidence (Smith et
al. 1989). In addition, spherical epi-
dermal cells would focus light to the
shallow depths that are necessary for
these typically thinner shade leaves.
In sunnier habitats, more elliptical
epidermal cells would generate
deeper focal points for a more even
distribution of internal light through-
out thicker leaves (Vogelmann et al.
1996a). Moreoever, any bending of
incident, direct-beam sunlight by epi-
dermal cells is important for length-
ening photon path lengths inside the
leaf and, thus, increasing the prob-

ability for absorption by chloroplasts
(Vogelmann et al. 1996b).
Mesophyll. The optical properties of
cell layers inside leaves (i.e., the pali-
sade and spongy mesophyll) also
appear to regulate the internal distri-
BioScience Vol. 47 No. 11 786
bution of sunlight for enhanced pho-
tosynthesis (Vogelmann 1993, Vogel-
mann et al. 1996a). For example, the
more columnar palisade cells typical
of thick sun leaves act as light con-
duits that propagate light deeper into
the mesophyll (Figure 1), thus dis-
tributing light more evenly through-
out the leaf (Terashima 1989, Vogel-
mann and Martin 1993). In addition,
the cell walls of the spherical spongy
mesophyll cells and the large frac-
tion of air space in the leaf interior
generate large quantities of scattered
light, increasing light absorption by
chloroplasts within the mesophyll
(DeLucia et al. 1996). Overall, inter-
nal light scattering within leaves gen-
erates photon fluence levels three to
four times greater than sunlight inci-
dent on the leaf surface, enhancing
the absorption of weakly absorbed
wavelengths in particular (Vogel-
mann 1993).

Lower epidermis. Another funda-
mental influence of epidermal struc-
ture on photosynthesis may result
from leaf bicoloration, in which the
leaf side that faces away from the
sun is lighter in color than the leaf
surface facing toward the sun.
Bicoloration is especially common in
species that occupy more shaded
habitats (Smith 1981). Bicoloration
could enhance "light-trapping" in
the spongy mesophyll by providing a
reflective surface on the internal side
of the lower epidermis (Lin and
Ehleringer 1983, Smith 1981,
Woolley 1971). In these studies, re-
moval of the lower epidermis of a
bicolored leaf resulted in large in-
creases in light transmittance. The
reflective properties of the spongy
mesophyll and of the inside of the
lower epidermis are also important
for increased light retention and ab-
sorption in bicolored leaves (DeLucia
and Nelson 1993, DeLucia et al.
1996).
Light and carbon dioxide
gradients in leaves
It is reasonable to expect leaf orien-
tation and structure to interact so
that high light areas inside a leaf are
matched with high carbon dioxide
concentrations. Otherwise, full pho-
tosynthetic potential will not be

achieved (Figure 1). Although sub-
stantial gradients in light do appear
to form across the leaf mesophyll
(Vogelmann et al. 1996a), with cor-
responding effects on whole-leaf pho-
tosynthesis, carbon dioxide levels
inside leaves have not been mea-
sured directly, and much less is
known about their characteristics
(Parkhurst 1994). However, rela-
tively large gradients of carbon di-
oxide across the mesophyll thickness
have been estimated (Parkhurst 1978)
using indirect methods that measure
carbon dioxide exchange in whole
leaves that are exposed to carrier
gases infused from different sides of
the leaf (Parkhurst and Mott 1990).
Estimates of up to a 16 Pa pressure
difference in internal carbon dioxide
between opposite leaf sides have been
reported for leaves with large, ex-
perimental differences in ambient
carbon dioxide concentrations be-
tween the two leaf surfaces and nearly
equal numbers of stomata on both
sides of the leaf (Parkhurst et al.
1988). Actual gradients of carbon
dioxide inside natural leaves may be
less, although the common occur-
rence of stomata on only one side of
the leaf would enhance steeper gradi-
ents that would be in opposition to the
light gradient (Figure 1). Parkhurst
(1994) concluded that intercellular

gaseous diffusion is a substantial limi-
tation to photosynthetic carbon di-
oxide assimilation in the large num-
ber of species that have thick leaves
and stomata on the lower leaf sur-
face only. To date, measurements of
both light and carbon dioxide gradi-
ents within the same leaf are not
available for any plant species.
Although carbon dioxide gradi-
ents have not been measured directly
inside leaves, experiments using pulse
dosages of labeled carbon dioxide,
with subsequent paradermal section-
ing and autoradiography, have
shown variation in the location of
carboxylation activity inside leaves
(Nishio et al. 1993). Initial studies
indicated that the internal light gra-
dients of sun and shade leaves of
spinach did not correspond to the
carbon fixation gradient (Nishio et
al. 1993). However, a subsequent study
reported that light absorption profiles
predicted from chlorophyll concen-
tration gradients did match carbon
dioxide fixation profiles measured
within spinach leaves (Evans 1996),
although this study did not measure
internal light and carbon dioxide.
Logically, photosynthesis could be
maximized if chloroplasts were situ-
ated at locations within the meso-

phyll at which both light levels and
carbon dioxide availability were op-
timized by the appropriate combina-
tion of leaf orientation and struc-
ture. The observation that mesophyll
cell surface area, chlorophyll con-
centration, and photosynthetic ac-
tivity per unit leaf thickness are not
uniform across the leaf thickness in-
dicates that certain strata of the leaf
may experience an optimum overlap
of the opposing light (from above)
and carbon dioxide (from below)
gradients (Terashima and Hikosaka
1995). Evaluation of the relation-
ship among leaf thickness, stomatal
distribution, and whole-leaf photo-
synthesis could provide ecophysiologi-
cal evidence for the importance of the
overlap of light and carbon dioxide
gradients inside the leaf.
The interaction of leaf
orientation and structure
If leaf orientation and structure do
interact to regulate sunlight absorp-
tion and distribution inside the leaf,
then the structural asymmetry iden-
tified above (e.g., epidermal lens cells
and palisade cells beneath the upper
leaf surface of horizontal leaves)
should correspond to the quantity
and type of sunlight incident on each
leaf surface. The focusing capabili-
ties of epidermal lens cells require
direct-beam sunlight (diffuse light is

poorly focused by any lens), whereas
palisade cells, if they function to
propagate light deeper into the leaf,
should occur beneath the leaf sur-
face with greatest incident light. If
carbon dioxide is to be supplied ad-
equately to the increased mesophyll
cell area in sun leaves, then the cor-
responding increase in leaf thickness
should be accompanied by a more
equal distribution of stomata on both
leaf sides. However, few ecological
studies have related the occurrence
of these structural differences in leaf
symmetry, thickness, and stomatal
distribution with differences in inci-
dent light between the two leaf sur-
faces under natural field conditions.
One might also expect to find
changes in leaf structure that would
December 1997 787
diminish light absorption when a
plant is experiencing other sources
of stress-that is, when light is not
limiting but temperature, water, or
nutrients may be. Numerous studies
have documented the detrimental
impact of high light on photosyn-
thetic performance, especially when
a plant is under stress from other
environmental factors (Baker and

Bowyer 1994). For example, one
rarely observes leaves of any species
oriented perpendicular to full sun-
light, unless leaf temperatures are
low and transpirational water is
abundant (Smith 1978). High inci-
dent sunlight will result in leaf wilt
(midday wilt) even for plants whose
roots are in water-saturated soil
(Young and Smith 1980).
One of the best-documented ob-
servations of ecological patterns in
leaf structure, already mentioned
above, is the ability of most species
to develop sun leaves under high
sunlight exposure (e.g., Boardman
1977, Hansen 1917). In general, sun
leaves are smaller in dimension (at
least width, if not also length) but
greater in thickness (e.g., De Soyza
and Kinkaid 1991, Johnson 1978,
Nobel 1991, Smith 1978). This re-
duced leaf dimension in sun leaves
generates a significant increase in
convective heat dissipation, an im-
portant factor for plant survival in
drier, high-sun habitats, where over-
heating and high transpiration rates
are detrimental (Gates 1980).
The greater leaf thickness charac-
teristic of sun leaves results in a sub-
stantial increase in mesophyll cell
surface area for carbon dioxide ab-
sorption, providing a structural

mechanism for the observed increases
in photosynthesis per unit leaf area,
even though photosynthesis per unit
leaf biomass may remain unchanged
(Nobel 1980). A greater mesophyll
cell area also generates greater wa-
ter-use efficiency because of the sub-
stantially greater impact on carbon
dioxide uptake than transpirational
water loss. For species native to the
most sun exposed, stressful habitats
(e.g., desert shrubs, subalpine and
boreal conifer trees), smaller, thicker
leaves become almost cylindrical,
with a more inclined leaf orienta-
tion. Similarly, photosynthetic stems
commonly replace true leaves in ev-
ergreen shrubs of hot deserts, and
the frequent appearance of species
with leaf and stem succulence (e.g.,
cacti and euphorbs) are further ex-
amples of the occurrence of cylindri-
cal geometry in highly stressful habi-
tats. (We address the functional
significance of a cylindrical leaf form
in terms of light and carbon dioxide
processing for photosynthesis in the
next section.)
Most terrestrial plant species with
thin, laminar leaves have many more
stomata on the lower side of the leaf
than on the upper side (i.e., they are
hypostomatous), although a signifi-
cant fraction (including most grasses)

have almost equal numbers of sto-
mata on both leaf surfaces (i.e., they
are amphistomatous; Meidner and
Mansfield 1986). Only a few species
with thin, laminar leaves have sto-
mata exclusively on the upper leaf
side (e.g., lily pads; Brewer and Smith
1995). Increased leaf thickness has
been associated with a more equal
number of stomata on both leaf sur-
faces for numerous species and taxa
(Parkhurst 1978). Mott and Michael-
son (1991) reported that increased
incident light generated an increase
in both leaf thickness and the num-
ber of stomata on the upper leaf
surface in Ambrosia cordifolia. Hav-
ing stomata on both sides of a thicker
sun leaf may increase the supply of
carbon dioxide to the mesophyll cells
(Mott et al. 1982, Parkhurst 1994,
Parkhurst and Mott 1990). These
studies provide evidence that the
presence of stomata on both leaf
surfaces greatly enhances carbon di-
oxide supply to the greater meso-
phyll cell area found in thicker sun
leaves, both of which may be neces-
sary to support the greater photo-
synthetic rates per unit leaf surface
area. Thus, both stomatal distribu-
tion and mesophyll cell area contrib-
ute to the higher rates of photosyn-
thesis in sun leaves.
In a recent study, leaf structural

and orientational data were collected
for numerous evergreen species from
five communities in Western Austra-
lia to evaluate possible associations
between leaf structure and orienta-
tion (Smith et al. in press). These
communities occur along opposing
gradients in annual rainfall and daily
incident sunlight due to an increase
in understory species in the more
mesic communities. At the time of
sampling, the five communities were
composed of a high diversity of ever-
green species only, whose leaves must
endure seasonal drought (Beard
1990, Pate and McComb 1982). Such
stress "tolerators" may be particu-
larly indicative of adaptive relation-
ships between leaf form and func-
tion (Fahn and Cutler 1992, Levitt
1980).
For the five Australian communi-
ties, strong positive correlations oc-
curred between total daily sunlight
and the proportion of species in a
given community with thicker leaves,
more cylindrical leaves, an inclined
leaf orientation, palisade cell layers
on both leaf sides, and stomata on
both leaf sides (Smith et al. in press).
Also, the presence of palisade cell
layers on both leaf sides was corre-
lated more strongly with a lower
ratio (top-to-bottom) of incident sun-

light than with the total amount of
sunlight incident on the upper leaf
surface only. By contrast, the num-
ber of species with distinctly bicol-
ored leaves (with the top side darker
than the bottom side) was greater in
the more mesic, shaded communi-
ties. Because these understory spe-
cies also had typical shade leaf struc-
ture, leaf bicoloration was strongly
correlated with the thin, laminar leaf
structure and horizontal leaf display.
Similarly, leaf bicoloration was
nearly ubiquitous in understory
plants of the subalpine zone of the
Rocky Mountains (Smith 1981).
Corresponding changes in leaf
orientation and structure in response
to seasonal changes in stress is an-
other example of the strong interac-
tion between leaf structure and ori-
entation. For example, the numerous
drought-deciduous species in the
deserts of the southwestern United
States develop large, ephemeral
leaves with horizontal orientation
soon after rainfall (Beatley 1974).
As the soil dries, these initial leaves
are replaced by smaller, more in-
clined leaves. With increasing soil
dryness, numerous species shed these
leaves and only green stems remain,
generating a more inclined arrange-
ment of curved photosynthetic sur-
faces within the crown. Smith and

Nobel (1977, 1978) also reported
that high incident light had the great-
est effect on leaf morphology (e.g.,
size, thickness, pubescence) and
Table 1. Influence of incident sunlight and stress level of the
habitat on leaf orientational and structural characteristics and
on photosynthetic potential in 234 species (86 families) of
native plants (sampled predominantly from five Western
Australia
communities). Modified slightly from Smith et al. 1997.
Environmental conditions
High sun,a High sun, Low sun,a Low sun,
Leaf form low stressb high stressb low stress high stress
Orientation Horizontal; tracks the sun Vertical or cylindrical;
Horizontal Horizontal
avoids the sun
Top-to-bottom ratio of >3.5c <2.0 <3.5 2.5-3.5
incident light
Thickness (mm) >600 400-600 <400 <300
Thickness-to-width ratio <0.1 >0.1 <0.1 >0.1
Morphology Large laminar broad-leaf Small and cylindrical
Large laminar broad-leaf Small linear or laminar
broad-leaf
Hypostomatous and Amphistomatous Hypostomatous
Hypostomatous
amphistomatousd

Structures to protect No bicoloration Bicoloration Weak
bicoloration
abaxial stomata;
no bicoloration
Anatomy Upper palisade layers Upper and lower Single or no
palisade layer No palisade layer
palisade layers
Maximum photo- 1 2 3 4
synthetic potentiale
aDaily incident sunlight values computed over a 12-hour day
were considered "high" if photosynthetically active radiation
(PAR) was over
40 mol * m-2 * d-~ (as measured by a horizontal sensor) and
"low" if PAR was less than 10 mol * m-2 * d-1.
bStress was considered "high" if annual precipitation was less
than 7 cm and "low" if it was greater than 10 cm.
cAll values indicated for each category are rounded off to the
nearest significant figure (e.g., to the nearest 100 for leaf
thickness).
dLeaves were classified as hypostomatous if more than 70% of
the total leaf stomata were on the leaf underside; otherwise,
they were classified
as amphistomatous.
eRelative ranking: 1 is greatest and 4 is least.
anatomy (mesophyll cell surface area
and palisade development) in several
drought-deciduous shrubs. How-
ever, high light and temperature com-
bined with low water stress gener-
ated the thickest leaves. Thus,
sunlight exposure and the level of
water stress all interacted to signifi-

cantly influence leaf structure.
Korner et al. (1989) came to similar
conclusions about the effects of tem-
perature and light on leaf structure
in high-elevation plants of the Cen-
tral Alps.
Table 1 and Figure 2 present a
synthesis, based on four generalized
permutations of sunlight exposure
and stress level in a habitat, that
associates leaf orientational and
structural characteristics with pho-
tosynthetic potential. Plant species
that have leaves with the greatest
photosynthetic capacity occur in
high-light, low-stress situations and
have corresponding orientational and
structural features that generate high
photosynthetic rates-that is, hori-
zontal, thicker leaves with multiple
palisade layers on the leaf side facing
the sun, and a more equal number of
stomata on both leaf sides. As sun-
light and stress increase, leaf orienta-
tion becomes more inclined, with re-
duced sunlight interception, whereas
leaf structure becomes more symmetri-
cal (e.g., palisade cells occur on both
top and bottom of mesophyll). With
excessive sunlight exposure and
stress, leaves become cylindrical, and
the resulting radial diffusion elimi-
nates the need for asymmetry in in-
ternal anatomy. For species adapted

to low-light regimes (i.e., that have
horizontal, thin leaves with no pali-
sade cells, and stomata only on the
leaf underside), photosynthetic po-
tential is low (Table 1 and Figure 2).
These differences in leaf structure
and photosynthetic potential can
change within the same plant or
among plants of a given habitat, ac-
cording to seasonal changes in sun-
light exposure or stress.
Evolutionary perspective
The simplest explanation for the
patterns in leaf structure and orien-
tation discussed above is that during
their evolution, terrestrial plants re-
sponded to the amount of sunlight
and stress in a given habitat by evolv-
ing leaf structural properties in con-
cert with leaf orientational capabili-
ties (Table 1 and Figure 2). This
interactive evolution between leaf
orientation and structure probably
began in heavily shaded, humid
microsites that were close to the
ground (Thomas and Spicer 1987).
The evolution of thin, laminar, hori-
zontal leaves led to the most efficient
interception of sunlight.
The restriction of stomata to the
underside of shade leaves may have
been necessary to prevent photo-oxi-
dative damage to the chlorophyll-

containing guard cells in the epider-
mis (Baker and Bowyer 1994). Even
today, only extreme shade plants
have been reported to have abun-
dant chloroplasts in the upper epi-
dermis (Lee 1986), and most species
with stomata on the upper leaf sur-
face that are exposed to direct sun-
light have guard cells sunken in pits
and covered by epidermal projec-
tions, such as highly reflective pu-
bescence (Uphof and Hummel 1962).
Moreover, stomata on the underside
of horizontal leaves in wind-shel-
tered microsites experience much
higher humidity, due to the buoy-
ancy effects on water vapor; thus,
transpiration is substantially lower
for the same degree of stomatal
opening and photosynthetic car-
bon dioxide gain (Foster and Smith
1986).
December 1997 789
Lower/upper
incident light
Figure 2. The interaction between leaf structure and orientation,
and the amount of
sunlight incident on the top and bottom of the leaf, according to
the environmental
conditions listed in Table 1. Numbers correspond to the
rankings that are given for

photosynthetic potential in Table 1, and the cross-sections show
the corresponding
structural and orientational features of each type of leaf.
Shade species would also benefit
by evolving leaves with more spheri-
cal epidermal cells in the upper epi-
dermis for enhanced light gathering
and more shallow focal points (i.e., a
thin leaf), as well as from a bicolored
leaf with an internally reflective lower
epidermis for greater light trapping
(Table 1 and Figure 2). There is also
evidence that stomatal opening and
closing in hypostomatous shade
leaves occur in response to the much
greater amount of sunlight that is
incident on the upper leaf surface
(over 20-fold greater) and propa-
gates to the lower epidermis, where
the stomata are present (Smith 1981).
This scenario implies that the guard
cells of these abaxial stomata re-
spond to the light incident on the
upper, opposite leaf surface, where
few, if any, stomata are present. This
stomatal response to light absorbed
from the upper leaf surface would
have enabled a better coupling be-
tween available light for photosyn-
thesis (predominantly from above)
and carbon dioxide supply from the
lower leaf surface.
An internally reflective lower epi-

dermis (leaf bicoloration) would en-
sure that this propagated light would
not escape the leaf interior. More
spherical epidermal cells and bicolor-
ation would act to enhance light col-
lection in a light-limited habitat and
retention of absorbed light within
the leaf, respectively. Thus, in low-
light environments, the evolution of
thin, horizontal, bicolored laminar
leaves with stomata limited to the
leaf underside was probably the re-
sult of selective pressure for maxi-
mizing light capture, avoiding the
harmful effects of exposing stomata
(with their chlorophyll-containing
guard cells) to direct sunlight, and
minimizing transpirational water
loss. Internal distribution of absorbed
light and carbon dioxide was prob-
ably not a problem for such thin
leaves. This scenario may be repre-
sentative of the first vascular plants,
which successfully exploited atmos-
pheric carbon dioxide in low-light,
humid environments that were con-
tiguous with aquatic habitats (Tho-
mas and Spicer 1987, Ziegler 1987).
As land plants evolved to tolerate
and use higher levels of incident sun-
light, leaf structure evolved toward
the so-called sun leaf (Esau 1977).
Although it was an advantage to
present a smaller leaf dimension to

the wind to enhance convective cool-
ing (e.g., De Soyza and Kinkaid
1991), sun leaves also became
thicker, with the addition of pali-
sade cell layers on the upper surface.
By increasing the absorbing area for
carbon dioxide in the mesophyll and
allowing for more efficient light
propagation deeper into a thicker
leaf, these palisade cell layers en-
abled increased photosynthesis per
unit leaf area. However, the evolu-
tion of thicker leaves in high-sun
microhabitats may have presented a
new problem-how to efficiently use
absorbed light coming from the up-
per leaf surface, while carbon diox-
ide is diffusing from the opposite
surface.
Maximizing photosynthesis per
unit leaf biomass requires that both
carbon dioxide and light be distrib-
uted efficiently within the leaf. Al-
though in thick-leaved species, sto-
mata are more frequent on the upper
side of the leaf than they are in thin-
leaved species, in concert with the
greater photosynthetic capabilities
and carbon dioxide demand of
thicker leaves, guard cells of thick
leaves still may require protection
from full sun by the cuticle or such
epidermal features as pubescence and
sunken pits (Fahn and Cutler 1992,
Uphof and Hummel 1962). Another

strategy to avoid damage from ex-
cessive sunlight is a more inclined
leaf display, which probably occurred
early in the evolution of sun leaves
(Gamon and Pearcy 1989). In addi-
tion, as leaves became more inclined
(with lower and more equal amounts
of daily sunlight incident on both
leaf surfaces), the addition of epider-
BioScience Vol. 47 No. 11
2
Sun exposure
and stress
J
790
mal lens cells and palisade cell layers
to both sides of the leaf was neces-
sary for more effective capture,
propagation, and distribution of light
throughout the mesophyll. As de-
scribed previously, stomata on the
upper leaf surface appear to be most
common when leaves are thicker and
leaf orientation is inclined, so that
incident light on the chlorophyll-
containing guard cells is reduced. It
remains to be determined whether
epidermal cell shape and focusing

properties can also adjust to incident
light level.
In environments with the greatest
sun exposure, especially those with
concurrent stresses, such as water
limitation, the ultimate evolution of
leaf form appears to be toward a
more cylindrical instead of laminar
leaf (Table 1 and Figure 2). The
reduction in leaf width enhanced
convective heat dissipation, and the
surface curvature reduced incident
sunlight; together, these lowered leaf
temperatures and transpiration and
may have led to the evolution of the
more radial, cross-sectional geom-
etry of cylindrical leaves. Incident
light on a cylindrical leaf is substan-
tially reduced over the leaf surface,
regardless of leaf orientation, be-
cause of the increased angle of inci-
dence (i.e., the cosine law) generated
by the curved leaf surface (Jordan
and Smith 1993, Smith and Brewer
1994). However, with even a slight
inclination away from the sun, a leaf
with a curved surface experiences a
compound reduction in incident sun-
light. In addition, leaves with a higher
volume-to-surface area ratio desic-
cate more slowly and have greater
mechanical strength to withstand as-
sociated factors such as high wind
and herbivory (e.g., spiny leaves).

The cylindrical shape and radial
geometry of leaves of high-light spe-
cies in high-stress habitats may also
create advantages that are related
directly to the distribution of light
and carbon dioxide inside the leaf.
Extant species with cylindrical leaves
(e.g., conifers) tend to have a more
even distribution of stomata over the
entire leaf surface, possibly as a re-
sult of the reductions in incident
light described above. Stomatal guard
cells (with chloroplasts) will receive
less intense light on a curved surface.
The radial diffusion characteristic of
SHADE LEAF
SUN LEAF
MESOPHYLL AREA TO A
LEAF AREA RATIO
LOW STRESS HIGH STRESS
PHOTOSYNTHESIS PER UNIT LEAF AREA +
EPIDERMAL PALISADE SPONGY LEAF STOMATAL
LENS CELLS MESOPHYLL MESOPHYLL BICOLORATION
DISTRIBUTION
LIGHT LIGHT INTERNAL LIGHT LIGHT CO2 CAPTURE;
CAPTURE PROPAGATION SCATTER;CO2 TRAPPING
INTERNAL
CAPTURE DISTRIBUTION

ORIENTATION
// / >^ ^^^REFLECTANCE CYLINDRICAL;
CLRADIAL
Wt / /^^~~ >^ .^^^ ~GEOMETRY
REGULATION OF LIGHT
AND CO2 INSIDE LEAF
CONCENTRATION OF LIGHT
AND CO2 GRADIENTS
MAXIMUM PHOTOSYNTHESIS A
PER UNIT LEAF BIOMASS I
Figure 3. Leaf structural components involved in the evolution
of sun leaf photo-
synthesis. The interaction of leaf structural characteristics
influences photosyn-
thetic light and carbon dioxide capture and processing,
photosynthetic rate per unit
leaf area, and, ultimately, photosynthesis per unit leaf biomass.
During the evolu-
tion of shade to sun leaves, the development of a thicker leaf
with greater mesophyll
area and carbon dioxide assimilation capabilities led to greater
photosynthesis per
unit leaf area. However, this change must have been
accompanied by the evolution
of numerous other structural features (e.g., epidermal lens cells,
palisade and
spongy mesophyll cell layers, leaf bicoloration, and stomatal
distribution patterns)
that contributed to the regulation of internal light and carbon

dioxide gradients for
maximum photosynthesis per unit leaf biomass. Leaf orientation
away from the
sun, leaf reflectance of incident sunlight, and the evolution of
more cylindrical
leaves with radial diffusion properties probably reflect the
extent to which plants
leaves have evolved to cope with excessive sunlight and stress.
See text for a more
detailed explanation.
cylinders dictates that both absorbed
light and carbon dioxide should be-
come more concentrated with greater
distance from the epidermis (Nobel
1991). Thus, light propagation and
carbon dioxide diffusion to greater
depths in a thicker leaf should be
considerably less of a problem in a
cylindrical leaf than a laminar one.
Accordingly, leaf bicoloration, pali-
December 1997 791
sade cell layers, and such epidermal
features as pubescence may be un-
necessary and, thus, are rare for spe-
cies with cylindrical leaves (Table 1).
Conclusions
As Figure 3 indicates, numerous leaf
structural parameters appear to in-
fluence whole-leaf photosynthesis

through effects on light capture at
the leaf surface, as well as via its
propagation and attenuation within
the leaf. These structural adapta-
tions are strongly linked to leaf ori-
entation and to the total sunlight
incident on both leaf surfaces (Table
1 and Figure 2). The evolution of
greater leaf thickness in sun leaves
and corresponding structural asym-
metry according to leaf inclination is
strong evidence that both leaf orien-
tation and structure influence light
and carbon dioxide processing at the
whole-leaf level. In the case of a
characteristically thin shade leaf, for
which light, and not carbon dioxide
supply, is the primary limitation to
photosynthesis, this optimum zone
of light and carbon dioxide overlap
may be broader and closer to the
center of the leaf (Figure 1). More-
over, shade-type plants grow in loca-
tions (e.g., forest understories) that
are sheltered from wind (as well as
sun) and in which carbon dioxide
therefore commonly accumulates to
above-normal levels, lessening the
problem of carbon dioxide supply.
As a leaf becomes thicker with
higher sun exposure, and stomata
and palisade cell layers become com-
mon on both leaf sides (broadening
the zone of light and carbon dioxide
overlap inside the leaf), photosyn-

thesis per unit leaf area increases
and, therefore, so does light-use effi-
ciency (the amount of sunlight ab-
sorbed per carbon dioxide that is
assimilated for photosynthesis; Fig-
ures 1 and 2). The presence of epider-
mal lens cells and palisade cell layers
generates a more efficient distribution
of internal light and a greater photo-
synthetic rate per unit leaf biomass,
or photosynthetic efficiency.
As sunlight and stress become ex-
cessive, leaf orientation becomes
more inclined relative to the sun,
with a concomitant increase in leaf
symmetry (e.g., palisade on both leaf
sides). In the most sun exposed, high
stress habitats (or at the most stress-
ful times of year), leaves become
more cylindrical and more inclined
in orientation, reducing the negative
impact of high sun exposure and
eliminating the need for palisade cells
due to the concentrating effects of
radial diffusion on internal light and
carbon dioxide (Figures 2 and 3).
Future studies that attempt to ex-
plain the relationships between leaf
form and function, as related to pho-
tosynthetic performance, should be
directed toward identifying the
mechanisms that control light and
carbon dioxide gradients inside

leaves, as well as the corresponding
effects of these mechanisms on whole-
leaf photosynthesis (Figure 3). The
relationship between leaf form and
light and carbon dioxide capture and
processing that we have described in
this article provides an important
perspective for evaluating the im-
pact of future global climate change
scenarios (e.g., elevated atmospheric
carbon dioxide) on the survival of
species with different leaf forms. For
example, the proliferation of species
with leaves whose photosynthesis ap-
pears to be limited by carbon diox-
ide capture and processing (i.e., in
which stomatal distribution and leaf
thickness are constraints) may be
favored in a high-carbon dioxide
atmosphere.
Acknowledgments
We thank Richard Thompson, Fiona
Webster, and especially Shelley James
for editorial and field assistance. Fi-
nancial support for this project was
provided by grants to W. K. Smith
from the International Programs
Division and to T. C. Vogelmann
and W. K. Smith from the Integrative
Plant Biology Program of the Na-
tional Science Foundation, plus a
University of Western Australia
Department of Botany Summer
Scholarship.

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Article
Contentsp.785p.786p.787p.788p.789p.790p.791p.792p.793Issue
Table of ContentsBioScience, Vol. 47, No. 11 (Dec., 1997), pp.
721-816Volume Information [pp.809-816]Front Matter [pp.721-
807][Introduction]LettersThe Value of Dressed-up Nonsense
[p.723]The Real Limit to Tree Height [pp.723-724]A Question
of Emotional Baggage [p.724]FeaturesHow Wild Wolves
Became Domestic Dogs [pp.725-728]Out on a Limb [pp.729-

731]Washington Watch: Endangered Species Legislation
[p.733]Himalayan Forests and Ecological Generalizations
[pp.735-745]Economic and Environmental Benefits of
Biodiversity [pp.747-757]Fires, Hurricanes, and Volcanoes:
Comparing Large Disturbances [pp.758-768]The Natural Flow
Regime [pp.769-784]Leaf Form and Photosynthesis [pp.785-
793]Thinking of BiologyIn Dispraise of Reductionism [pp.795-
797]AIBS News [p.798]BooksPersonal Science: Cancer and the
Environment [pp.801-802]Spatiotemporal Perspective on
Conservation [pp.803-804]Science Redefines Perceptions of
Aging [pp.804-806]New Titles [p.806]BioBriefs [p.808]Back
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clearly and easily, and get the information needed to keep
students on track throughout the course with the new Reporting
Dashboard. Available via the MyLab Gradebook and fully
mobile-ready,
the Reporting Dashboard presents student performance data at
the
class, section, and program levels in an accessible, visual
manner.
• Accessibility (ADA)—Pearson is working toward WCAG 2.0
Level AA
and Section 508 standards, as expressed in the Pearson
Guidelines for
Accessible Educational Web Media. Moreover, our products
support
customers in meeting their obligation to comply with the
Americans with
Disabilities Act (ADA) by providing access to learning
technology programs
for users with disabilities.
Please email our Accessibility Team at [email protected] for the
most
up-to-date information.
• LMS Integration—You can now link from Blackboard Learn,
Brightspace by
D2L, Canvas, or Moodle to MyISLab. Professors can acess
assignments, rosters,
and resources, and synchronize grades with your LMS
gradebook.
Single sign-on provides students access to all the personalized
learning resources that make studying more efficient and

effective.
• Branching, Decision-Making Simulations—students take on
the role
of manager as they make a series of decisions based on a
realistic business
challenge, fostering decision making and problem solving skills.
The simulations change and branch based on their decisions,
creating various scenario paths. At the end of each simulation,
students
receive a grade and a detailed report of the choices they made
with the
associated consequences included.
• Writing Space—Better writers make better communicators—
who become better managers. Designed to help
develop and assess concept mastery and critical
thinking, the Writing Space offers auto-graded
writing assignments, and assisted auto-graded writing
assignments so students can receive meaningful, personalized
feedback quickly and easily. And because of Intergration with
Turnitin®, Writing Space can check students’ work for
improper
citation or plagiarism.
A L W A Y S L E A R N I N G
Office 2016 Grader Projects—Students complete projects in
Excel and Access to demonstrate problem
solving, critical thinking, and data analysis skills. Projects are
automatically graded and include
feedback. Integrity tokens in each project prevent and detect
cheating.
•

PROBLEM
SOLVING
TEAMWORK DECISION
MAKING
CRITICAL
THINKING
ABILITY
TO APPLY
KNOWLEDGE
COMMUNICATION
NEW
HIR
E
Information systems have become pervasive. Mobile devices,
social media,
and cloud computing have transformed organizations and
society. The Internet
of Things can generate a wealth of potentially useful Big Data.
The rapid
development of transportation and telecommunication
technologies, national
and global infrastructures, and information systems as well as a
host of other
factors has created a number of pressing societal issues that
tremendously
influence the world we live in. These issues include
demographic changes,

urbanization, shifts in economic power, resource scarcity, and
climate change.
As a consequence, sustainable development will become an ever
increasingly
important aspect for organizations. Throughout this revision, we
discuss
how organizations can harness radical innovations and other
technological
developments, as well as the role of information systems in
influencing and
addressing pressing societal issues; further, we added a new
chapter element
about the role of Green IT. We designed the book’s cover to
emphasize how
IT resides within and influences various societal issues.
• Learning Catalytics™—is an interactive, student response
tool that
uses students’ smartphones, tablets, or laptops to engage them
in more
sophisticated tasks and critical thinking as well as collaboration
with other
class members. Included with MyLab with eText, Learning
Catalytics enables
you to generate classroom discussion, guide your lecture, and
promote
peer-to-peer learning with real-time analytics.
• Enhanced eText—keeps students engaged in learning on their
own time, while
helping them achieve greater conceptual understanding of
course material. The
embedded videos, simulations, and activities bring learning to

life.
to apply the very concepts they are reading about. Combining
resources that
illuminate content with accessible self-assessment, MyLab with
Enhanced eText
provides students with a complete digital learning experience—
all in one place.
• Dynamic Study Modules—help students learn the language of
MIS by
continuously assessing their activity and performance in real
time by adapting to the
student's knowledge and confidence on each concept. These are
available as
graded assignments prior to class, and accessible on
smartphones, tablets, and
computers.
• Reporting Dashboard—View, analyze, and report learning
outcomes
clearly and easily, and get the information needed to keep
students on track throughout the course with the new Reporting
Dashboard. Available via the MyLab Gradebook and fully
mobile-ready,
the Reporting Dashboard presents student performance data at
the
class, section, and program levels in an accessible, visual
manner.
• Accessibility (ADA)—Pearson is working toward WCAG 2.0
Level AA
and Section 508 standards, as expressed in the Pearson
Guidelines for
Accessible Educational Web Media. Moreover, our products
support

customers in meeting their obligation to comply with the
Americans with
Disabilities Act (ADA) by providing access to learning
technology programs
for users with disabilities.
Please email our Accessibility Team at [email protected] for the
most
up-to-date information.
• LMS Integration—You can now link from Blackboard Learn,
Brightspace by
D2L, Canvas, or Moodle to MyISLab. Professors can acess
assignments, rosters,
and resources, and synchronize grades with your LMS
gradebook.
Single sign-on provides students access to all the personalized
learning resources that make studying more efficient and
effective.
A L W A Y S L E A R N I N G
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330 Hudson Street, NY NY 10013
I N F O R M A T I O N S Y S T E M S T O D A Y
Joseph Valacich
University of Arizona
Christoph Schneider
City University of Hong Kong
M A N A G I N G I N T H E D I G I T A L W O R L D
E I G H T H E D I T I O N
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Dedication
To my mother Mary, you are the best.
—Joe
To Birgit for your love and support.
—Christoph
PM04/12/15 4:22 PM
vii
Joseph (Joe) Valacich is an Eller Professor of MIS within the
Eller College of Management
at the University of Arizona, a Fellow of the Association for
Information Systems (2009), and
the Chief Science Officer (CSO) of Neuro-ID, Inc. He was
previously on the faculty at Indiana

University, Bloomington, and Washington State University,
Pullman. He has had visiting faculty
appointments at City University of Hong Kong, Buskerud
College (Norway), the Helsinki School
of Economics and Business, the Norwegian University of Life
Sciences, and Riga Technical
University (Latvia). He received a PhD degree from the
University of Arizona (MIS) and MBA
and BS (Computer Science) degrees from the University of
Montana. Prior to his academic career,
Dr. Valacich worked in the software industry in Seattle in both
large and startup organizations.
Dr. Valacich has served on various national task forces
designing model curricula for the
information systems discipline, including IS ‘97, IS 2002, and
IS 2010: The Model Curriculum
and Guidelines for Undergraduate Degree Programs in
Information Systems, where he was
co-chairperson. He also served on the task force that designed
MSIS 2000 and 2006: The Master
of Science in Information Systems Model Curriculum. He
served on the executive committee,
funded by the National Science Foundation, to define the IS
Program Accreditation Standards
and served on the board of directors for CSAB (formally the
Computing Sciences Accreditation
Board) representing the Association for Information Systems
(AIS). He was the general confer-
ence co-chair for the 2003 International Conference on
Information Systems (ICIS) and the 2012
Americas Conference on Information Systems (AMCIS); both
were held in Seattle.
Dr. Valacich has conducted numerous corporate training and
executive development pro-

grams for organizations, including AT&T, Boeing, Dow
Chemical, EDS, Exxon, FedEx, General
Motors, Microsoft, and Xerox. He has served in a variety of
editorial roles within various
academic journals and conferences. His primary research
interests include human–computer
interaction, deception detection, technology-mediated
collaboration, mobile and emerging tech-
nologies, and e-business. He is a prolific scholar, having
published more than 200 scholarly
articles in numerous prestigious journals and conferences,
including: MIS Quarterly, Information
Systems Research, Management Science, Academy of
Management Journal, Journal of MIS,
Decision Sciences, Journal of the AIS, Communications of the
ACM, Organizational Behavior
and Human Decision Processes, and Journal of Applied
Psychology. He is a coauthor of the
leading textbooks Modern Systems Analysis and Design (8th
ed.) and Essentials of Systems
Analysis and Design (6th ed.), both published by Pearson.
In 2016, Dr. Valacich was awarded the University of Arizona,
Tech Launch Arizona, “Innova-
tion & Impact Award” for Information Technology. He was
awarded the “Distinguished Alumnus
Award” from the University of Montana Alumni Association in
2012 and the “Outstanding Alum-
nus Award” from the University of Montana’s School of
Business Administration in 2009. Dr.
Valacich is also ranked as one of the most prolific authors in
the history of MIS Quarterly—his
discipline’s top journal—over the life of the journal (1977–
2016) (see misq.org). Throughout his
career, he has also won numerous teaching, service, and
research awards.

Christoph Schneider is an assistant professor in the Department
of Information Systems at
City University of Hong Kong and previously held a visiting
faculty appointment at Boise State
University. He earned a Swiss Higher Diploma in Hotel
Management at the University Centre
César Ritz in Brig, Switzerland, a BA in Hotel and Restaurant
Administration at Washington
State University, and a PhD in Business Administration
(Management Information Systems)
at Washington State University. His teaching interests include
the management of information
systems and web design.
About the Authors
http://misq.org
viii ABOUT THE AUTHORS
Dr. Schneider is an active researcher. His primary research
interests include human–com-
puter interaction, electronic commerce, and computer-mediated
collaboration. His research has
appeared in peer-reviewed journals, such as Information
Systems Research, Management Infor-
mation Systems Quarterly, Management Science, and IEEE
Transactions on Professional Com-
munication; further, he has presented his research at various
international conferences, such as
the International Conference on Information Systems, the
European Conference on Informa-

tion Systems, and the Hawaii International Conference on
System Sciences. He serves as a
member of the International Steering Committee of the
International Conference on Informa-
tion Systems Development (ISD) and as senior editor at
Information Systems Journal.
ix
Preface xix
Chapter 1 Managing in the Digital World 2
Chapter 2 Gaining Competitive Advantage Through
Information
Systems 48
Chapter 3 Managing the Information Systems Infrastructure and
Services 90
Chapter 4 Enabling Business-to-Consumer Electronic
Commerce 138
Chapter 5 Enhancing Organizational Communication and
Collaboration Using Social Media 182
Chapter 6 Enhancing Business Intelligence Using Big Data and
Analytics 224
Chapter 7 Enhancing Business Processes Using Enterprise
Information
Systems 270

Chapter 8 Strengthening Business-to-Business Relationships
via Supply
Chain and Customer Relationship Management 306
Chapter 9 Developing and Acquiring Information Systems 344
Chapter 10 Securing Information Systems 390
Technology Briefing Foundations of Information Systems
Infrastructure 442
Acronyms 491
Glossary 493
Name Index 513
Organization Index 514
Subject Index 517
Brief Contents
PM04/12/15 4:22 PM

xi
Preface xix
Chapter 1 Managing in the Digital World 2
MANAGING IN THE DIGITAL WORLD: Open Innovation 2
Information Systems Today 4
The Emergence of the Digital World 4
Globalization and Societal Issues in the Digital World 7
◾ COMING ATTRACTIONS: Memory Crystals 7
Five IT Megatrends That Shape the Digital Future 10
◾ WHO’S GOING MOBILE: Wearable Technologies 10
◾ GREEN IT: The Green Internet of Things 16
Information Systems Defined 16
Data: The Root and Purpose of Information Systems 18
Hardware, Software, and Telecommunications Networks: The
Components of
Information Systems 18
People: The Builders, Managers, and Users of Information
Systems 19
◾ SECURITY MATTERS: Ransomware 24
Organizations: The Context of Information Systems 25
◾ WHEN THINGS GO WRONG: Technology Addiction 28
The Dual Nature of Information Systems 29
Case in Point: An Information System Gone Awry: Outages
Outrage Gamers 29
Case in Point: An Information System That Works: FedEx 29
Information Systems for Competitive Advantage 30
◾ ETHICAL DILEMMA: The Social and Environmental Costs
of the Newest
Gadgets 31
IS Ethics 32

Information Privacy 32
Intellectual Property 36
The Need for a Code of Ethical Conduct 37
◾ INDUSTRY ANALYSIS: Business Career Outlook 38
Key Points Review 39 • Key Terms 39 • Review Questions 40 •
Self-
Study Questions 40 • Problems and Exercises 41 • Application
Exercises 42 • Team Work Exercise 42 • Answers to the Self-
Study
Questions 43
◾ APPLE 44
◾ HEALTHCARE IS 45
Chapter 2 Gaining Competitive Advantage Through Information
Systems 48
MANAGING IN THE DIGITAL WORLD: Startups and New
Business Models 48
Enabling Organizational Strategy through Information Systems
50
Organizational Decision-Making Levels 50
Organizational Functional Areas 52
Contents
http://amazon.com
xii CONTENTS

Information Systems for Automating: Doing Things Faster 53
Information Systems for Organizational Learning: Doing Things
Better 55
Information Systems for Supporting Strategy: Doing Things
Smarter 56
Identifying Where to Compete: Analyzing Competitive Forces
56
Identifying How to Compete: Choosing a Generic Strategy 57
Identifying How to Compete: Resources and Capabilities 58
◾ GREEN IT: The Electric Navy 59
Identifying How to Compete: Analyzing the Value Chain 60
The Role of Information Systems in Value Chain Analysis 60
The Technology/Strategy Fit 61
Business Models in the Digital World 61
◾ WHO’S GOING MOBILE: Digital Nomads 62
Revenue Models in the Digital World 62
◾ WHEN THINGS GO WRONG: The Pains of Uber in China
65
Platform-Based Business Models and the Sharing Economy 65
Service-Based Business Models 67
◾ ETHICAL DILEMMA: The Ethics of the Sharing Economy
68
Valuing Innovations 69
The Need for Constant IS Innovation 71
Successful Innovation Is Difficult 72
Open Innovation 73
Organizational Requirements for Innovation 74
◾ COMING ATTRACTIONS: The CITE Project 75
The Innovation Process 75
◾ SECURITY MATTERS: The Bangladesh SWIFT Theft 78
Startups and Crowdfunding 78
◾ INDUSTRY ANALYSIS: Education 80
Key Points Review 81 • Key Terms 81 • Review Questions 82 •

Self-
Study Questions 82 • Problems and Exercises 83 • Application
Study
Questions 84
◾ GROUPON 85
◾ STREAMING VIDEO 86
Chapter 3 Managing the Information Systems Infrastructure and
Services 90
MANAGING IN THE DIGITAL WORLD: From Google to
Alphabet 90
The IS Infrastructure 92
◾ �WHO’S GOING MOBILE: Mobile Payments Are
Transforming Developing
Countries 94
Applications and Databases Supporting Business Processes 96
◾ ETHICAL DILEMMA: Putting People’s Lives Online 97
IS Infrastructure Components 98
Hardware 98
System Software 100
Storage 102
◾ COMING ATTRACTIONS: Making Death Optional? 102
Networking 103
◾ GREEN IT: Alphabet Renewables 109
Data Centers 111
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CONTENTS xiii
Issues Associated with Managing the IS Infrastructure 112
Rapid Obsolescence and Shorter IT Cycles 112
Big Data and Rapidly Increasing Storage Needs 115
Demand Fluctuations 115
Increasing Energy Needs 116
Cloud Computing 116
◾ �WHEN THINGS GO WRONG: Old and Dirty Energy
Drives Global Internet
Growth 117
What Is Cloud Computing? 117
Managing the Cloud 121
Advanced Cloud Applications 124
◾ SECURITY MATTERS: Car Hacking 126
Green Computing 129
◾ INDUSTRY ANALYSIS: Movie Industry 130
Key Points Review 131 • Key Terms 131 • Review Questions
132 • Self-
Study Questions 132 • Problems and Exercises 133 •
Application
Study
Questions 135
◾ A CATALYST FOR INNOVATION: AMAZON WEB
SERVICES 135
◾ THE DARK WEB 136
Chapter 4 Enabling Business-to-Consumer Electronic
Commerce 138

MANAGING IN THE DIGITAL WORLD: Taobao and the
World of E-commerce 138
E-Commerce and E-Government 140
Types of Electronic Commerce 140
E-government 141
E-finance 142
Business-To-Consumer E-Commerce 143
◾ COMING ATTRACTIONS: The AI Hedge Fund 144
E-tailing: Capabilities and Opportunities 146
Benefits of E-tailing 149
◾ ETHICAL DILEMMA: The Ethics of Reputation
Management 150
Drawbacks of E-tailing 151
Electronic Commerce Websites and Internet Marketing 151
Designing Websites to Meet Online Consumers’ Needs 152
◾ SECURITY MATTERS: Too Small to Be Hacked? 152
Internet Marketing 154
◾ WHEN THINGS GO WRONG: Buying Likes 158
Mobile Commerce, Consumer-To-Consumer EC, and
Consumer-To-Business EC 159
C2C EC 161
C2B EC 162
Securing Payments and Navigating Legal Issues in EC 163
Securing Payments in the Digital World 163
◾ GREEN IT: Green Online Shopping 164
◾ WHO’S GOING MOBILE: Mobile Payments 165
Legal Issues in EC 168
◾ INDUSTRY ANALYSIS: Retailing 171

xiv CONTENTS
173 • Self-
Application
Study
Questions 176
◾ WEB ANALYTICS 177
◾ ROCKET INTERNET—CLONING BUSINESS MODELS 178
Chapter 5 Enhancing Organizational Communication and
Collaboration Using Social Media 182
MANAGING IN THE DIGITAL WORLD: Facebook 182
The Need for Communication and Collaboration 184
Virtual Teams 184
Groupware 185
Videoconferencing 186
◾ GREEN IT: Green IT Fueling Renewable Energy 188
Intranets and Employee Portals 188
The Evolving Web 190
◾ COMING ATTRACTIONS: Dissolvable Electronics 191
Evolving Web Capabilities 191
Evolving Social Interaction 192
The Evolving Workspace 193
Future Web Capabilities 193
Social Media and the Enterprise 194

Enhancing Communication Using Social Media 194
Enhancing Cooperation with Social Media 197
◾ SECURITY MATTERS: Terrorism Is Winning the Social
Media Battle 200
Enhancing Collaboration with Social Media 201
◾ WHO’S GOING MOBILE: Going SoLoMo: Yelp 203
Enhancing Connection with Social Media 205
◾ ETHICAL DILEMMA: Anonymity, Trolling, and
Cyberharassment 207
Managing Social Media Applications in the Enterprise 208
Organizational Issues 208
◾ WHEN THINGS GO WRONG: Crowdfunding Failures 210
Downsides and Dangers of using Social Media Applications 211
◾ INDUSTRY ANALYSIS: Online Travel 213
215 • Self-
Application
Study
Questions 218
◾ LIVING IN A BUBBLE: FACEBOOK, NEWSFEEDS, AND
JOURNALISM 218
◾ LIKE FARMING AND CLICKBAIT 219
Chapter 6 Enhancing Business Intelligence Using Big Data and
Analytics 224
MANAGING IN THE DIGITAL WORLD: Intelligence Through
Drones 224
Enhancing Organizational Decision Making 226
Why Organizations Need Business Intelligence and Advanced

Analytics 226
◾ �GREEN IT: Big Data, Internet of Things, and Analytics
Fuel Greener
Facilities 229
Databases: Providing Inputs into Business Intelligence and
Advanced
Analytics 229
CONTENTS xv
◾ WHEN THINGS GO WRONG: Twitter Fever—Look Before
You Tweet 233
◾ COMING ATTRACTIONS: Emotion Aware Gaming 239
Business Intelligence and Advanced Analytics 239
Business Intelligence 240
◾ WHO’S GOING MOBILE: Identifying Malaria Hotspots 245
Advanced Analytics 245
◾ ETHICAL DILEMMA: Orwellian Internet of Things 247
◾ �SECURITY MATTERS: Hacktivists Versus Fembots: The
Ashley Madison
Case 253
Knowledge Management and Geographic Information Systems
254
Knowledge Management Systems 254
Geographic Information Systems 257
◾ INDUSTRY ANALYSIS: Healthcare 260

262 • Self-
Application
Study
Questions 265
◾ NSA: NATIONAL SURVEILLANCE AGENCY? 265
◾ GATHERING SOCIAL INTELLIGENCE 266
Chapter 7 Enhancing Business Processes Using Enterprise
Information Systems 270
MANAGING IN THE DIGITAL WORLD: Amazon.com 270
Core Business Processes and Organizational Value Chains 272
Core Business Processes 272
Organizational Activities Along the Value Chain 274
◾ GREEN IT: Why Your Enterprise Systems Should Be in the
Cloud 277
Value Systems: Connecting Multiple Organizational Value
Chains 279
Enterprise Systems 279
The Rise of Enterprise Systems 280
Supporting Business Processes 281
◾ ETHICAL DILEMMA: Too Much Intelligence? RFID and
Privacy 282
◾ �COMING ATTRACTIONS: The Internet of Things Will
Transform ERP and
Organizations 285
Enterprise Resource Planning 288
Responding to Compliance and Regulatory Demands 289
Choosing an ERP System 289

◾ �SECURITY MATTERS: To Update or Not to Update, That
Shouldn’t Be the
Question 290
Enabling Business Processes Using ERP Core Components 291
ERP Installation 294
ERP Limitations 294
Achieving Enterprise System Success 294
◾ WHO’S GOING MOBILE: Big ERP Systems Embracing
Small Mobile
Devices 295
Secure Executive Sponsorship 295
Get Help from Outside Experts 296
Thoroughly Train Users 296
Take a Multidisciplinary Approach to Implementations 296
Evolve the Implementation 296
◾ �WHEN THINGS GO WRONG: Software Error Frees
Prisoners Early and Is
Linked to Killings 297
http://amazon.com
xvi CONTENTS
◾ INDUSTRY ANALYSIS: The Automobile Industry 298
300 • Self-
Application
Study

Questions 302
◾ SOFTWARE AS A SERVICE: ERP BY THE HOUR 303
◾ AMAZON’S ORDER FULFILLMENT, AUTOMATION,
AND TECHNOLOGICAL
UNEMPLOYMENT 304
Chapter 8 Strengthening Business-to-Business Relationships
via Supply Chain and Customer Relationship
Management 306
MANAGING IN THE DIGITAL WORLD: Walmart 306
Supply Chain Management 308
What Is a Supply Chain? 308
Business-to-Business Electronic Commerce: Exchanging Data in
Supply
Networks 308
Managing Complex Supply Networks 311
Benefits of Effectively Managing Supply Chains 312
Optimizing the Supply Chain Through Supply Chain
Management 314
◾ �WHEN THINGS GO WRONG: SpaceX Rocket Failure due
to Supply Chain
Failure 315
Developing an SCM Strategy 316
◾ GREEN IT: Nike’s Green Supply Chain 317
Supply Chain Planning 317
Supply Chain Execution 318
Supply Chain Visibility and Analytics 321
Customer Relationship Management 321
◾ COMING ATTRACTIONS: Augmenting Supply Chain
Success 322

◾ �SECURITY MATTERS: Disclosing the Customer Data of
the Most
Vulnerable 325
Developing a CRM Strategy 325
Architecture of a CRM System 326
◾ �WHO’S GOING MOBILE: Developing a Mobile CRM App
for
Customers 330
◾ ETHICAL DILEMMA: When Algorithms Discriminate 334
Ethical Concerns with CRM 335
◾ INDUSTRY ANALYSIS: Manufacturing 335
337 • Self-
Application
Study
Questions 339
◾ SUPPLY CHAIN HAVOC 340
◾ EFFICIENTLY DELIVERING PRODUCTS OVER THE
“LAST MILE” 341
Chapter 9 Developing and Acquiring Information Systems 344
MANAGING IN THE DIGITAL WORLD: The Maker Movement
344
Making the Business Case 346
Business Case Objectives 346
The Productivity Paradox 346
Making a Successful Business Case 348
◾ GREEN IT: Project Natick—Microsoft’s Underwater Data
Centers 350

CONTENTS xvii
◾ COMING ATTRACTIONS: Harvesting Human Energy 352
Presenting the Business Case 354
◾ ETHICAL DILEMMA: Ethical App Development 356
The Systems Development Process 357
Custom Versus Off-the-Shelf Software 357
Open Source Software 358
Systems Integration: Combining Custom, Open Source, and Off-
the-Shelf
Systems 359
IS Development in Action 359
The Role of Users in the Systems Development Process 361
Systems Development Controls 361
Steps in the Systems Development Process 361
◾ WHO’S GOING MOBILE: Creating Mobile Apps 362
Phase 1: Systems Planning and Selection 362
Phase 2: Systems Analysis 363
Phase 3: Systems Design 366
Phase 4: Systems Implementation and Operation 367
Repeating the SDLC: Systems Maintenance 369
◾ SECURITY MATTERS: Mobile Cybercrime 371
Other Approaches to Designing and Building Systems 371
Acquiring Information Systems 373
External Acquisition 373
◾ WHEN THINGS GO WRONG: Top Security Threats 374
Outsourcing Systems Development 378
◾ INDUSTRY ANALYSIS: Broadcasting 380

382 • Self-
Application
Study
Questions 385
◾ NEXT GENERATION IDENTIFICATION: FBI, ICE
DATABASES EXPAND AND
JOIN FORCES 386
◾ BIG DATA, HADOOP, MAP REDUCE 387
Chapter 10 Securing Information Systems 390
MANAGING IN THE DIGITAL WORLD: Not So
“Anonymous”—Activists,
Hacktivists, or Just Plain Criminals? 390
Computer Crime 392
Hacking and Cracking 392
Types of Computer Criminals and Crimes 392
◾ �GREEN IT: Anonymous Protests the Killing of Dolphins
and Whales in
Japan 396
Computer Viruses and Other Destructive Code 397
◾ �WHEN THINGS GO WRONG: The Bug That Almost
Killed the
Internet 402
Cyberharassment, Cyberstalking, and Cyberbullying 404
Software Piracy 404
Cybersquatting 406
Laws Against Computer Crime 406

Cyberwar and Cyberterrorism 407
◾ WHO’S GOING MOBILE: Backdoors in Every Mobile
Phone? 408
Cyberwar 408
Cyberterrorism 409
xviii CONTENTS
Foundations of Information Systems Infrastructure 442
Foundational Topics in IS Hardware 443
Input Technologies 443
Processing: Transforming Inputs into Outputs 445
Output Technologies 449
Foundational Topics in IS Software 450
System Software 451
Programming Languages and Development Environments 451
Foundational Topics in Networking 457
Evolution of Computer Networking 457
Types of Networks 459
Packet Switching 462
Network Standards and Protocols 462
Network Technologies 466
The Internet 472
Foundational Topics in Database Management 478
Relational Database Design 478
Advanced Database Models 483
Key Points Review 483 • Key Terms 484 • Review

Questions 485 • Self-Study Questions 486 • Problems and
Exercises 487 • Answers to the Foundational Hardware Self-
Study
Questions 489 • Answers to the Foundational Software Self-
Study
Questions 489 • Answers to the Foundational Networking Self-
Study
Questions 489 • Answers to the Foundational Database Self-
Study
Questions 489
Acronyms 491
Glossary 493
Name Index 513
Organization Index 514
Subject Index 517
TECHNOLOGY
BRIEFING
◾ �ETHICAL DILEMMA: Ethics and Cyberwar: Just Because
We Can, Should
We? 412
Managing Information Systems Security 412
Assessing Risks 414
Developing a Security Strategy 416
Implementing Controls and Training 418
◾ �SECURITY MATTERS: Back to the Future: Analog May
Be the Future of
Securing Critical Infrastructure 419

◾ COMING ATTRACTIONS: Can You Become Your
Password? 425
Monitoring Security 428
◾ INDUSTRY ANALYSIS: Cybercops Track Cybercriminals
431
433 • Self-
Application
Study
Questions 437
◾ STOPPING INSIDER THREATS: EDWARD SNOWDEN
AND THE NSA 438
◾ CHINA’S GREAT (FIRE) WALL 439
xix
Approach
Information systems have become pervasive. Mobile devices,
social media, and cloud computing
have transformed organizations and society. Organizations see
the possibilities of the Internet of
Things, in that not only computers but various sensors, motors,
actuators, or even cameras can
generate a wealth of potentially useful data. Businesses face
unprecedented opportunities, but
also challenges, through the ability to utilize Big Data. What
does all this mean? What are the
catalysts of these concepts and of all this change? More

important, how can organizations thrive
in this dynamic and highly competitive marketplace? The
answer to these and many similar ques-
tions is that information systems and related information
technologies are driving innovation, new
business models, and hypercompetiti on. It is little wonder that
teaching an introductory course on
information systems has never been more crucial—or more
challenging.
One of the greatest challenges that we face in teaching
information systems courses is how
to keep pace in the classroom with what is happening out in the
real world. Being relevant to
students while at the same time providing the necessary
foundation for understanding the breadth,
depth, and complexity of information systems has never been
more difficult. We wrote Informa-
tion Systems Today, Eighth Edition, with this overarching goal
in mind, to be both rigorous and
relevant. To accomplish this, we want students not only to learn
about information systems but
also to clearly understand the importance of information
systems for individuals, organizations,
and society. Additionally, we do not want to simply spoon-feed
students with technical terms and
the history of information systems. Instead, students must
understand exactly what innovative
organizations are doing with contemporary information systems
and, more important, where
things are heading. Finally, we want to empower students with
the essential knowledge needed to
be successful in the use and understanding of information
systems in their careers.
To this end, we wrote Information Systems Today, Eighth

Edition, so that it is contemporary,
fun to read, and useful, focusing on what business students need
to know about information sys-
tems to survive and thrive in the digital world.
Audience
Information Systems Today, Eighth Edition, is primarily for the
undergraduate introductory infor-
mation systems course required of all business students. The
introductory information systems
course typically has a diverse audience of students majoring in
many different areas, such as
accounting, economics, finance, marketing, general
management, human resource management,
production and operations, international business,
entrepreneurship, and information systems.
This book was also written for students studying topics outside
of business, especially in the
growing and broad area of information sciences. Given the
range of students taking this type of
course, we have written this book so that it is a valuable guide
to all students, providing them with
the essential information they need to know. Therefore, this
book has been written to appeal to a
diverse audience.
Information Systems Today, Eighth Edition, can also be used
for the introductory course
offered at the graduate level—for example, in the first year of
an MBA program. Such usage
would be especially appropriate if the course heavily focused on
the diverse set of cases provided
in each chapter.
What’s New to the Eighth Edition
Our primary goal for Information Systems Today, Eighth

Edition, was to emphasize the impor-
tance of information systems to all business students as the role
of information technology and
systems continues to expand within organizations and society.
Most notably, we extensively
Preface
xx PREFACE
examine how five big megatrends—mobile, social media, the
Internet of Things, cloud comput-
ing, and Big Data—are transforming individuals, organizations,
and society. Given this clear
focus, we are better able to identify those topics most critical to
students and future business
professionals. Consequently, we have made substantial revisions
to the basic content of the chap-
ters and pedagogical elements as well as introduced several new
elements that we believe help
achieve this goal. New or expanded chapter topics include the
following:
�■ An extensively revised chapter—Chapter 1, “Managing in
the Digital World”—focuses
not only on defining what an information system consists of but
also provides new content
on globalization and societal issues in the digital world as well
as the role of five IT mega-
trends in fueling and addressing these issues.
�■ An extensively revised chapter—Chapter 2, “Gaining

Competitive Advantage Through
Information Systems”—provides new content describing how
information systems play a
key part in enabling different types of innovation and
innovative business models.
�■ A revised chapter—Chapter 3, “Managing the Information
Systems Infrastructure and
Services”—provides updated content on the need for a reliable,
adaptable, and scalable
infrastructure to support the needs of today’s organizations as
well as on essential infra-
structure concepts related to hardware, software, storage,
networking and the Internet, data
centers, and cloud computing.
�■ A revised chapter—Chapter 4, “Enabling Business-to-
Consumer Electronic Commerce”—
provides updated content related to e-commerce involving the
end consumer as well as new
and expanded coverage of e-finance, fintech, and related issues.
�■ A revised chapter—Chapter 5, “Enhancing Organizational
Communication and Collabora-
tion Using Social Media”—centers around various topics related
to the need for organiza-
tional communication and provides updated content on how
individuals and organizations
use both traditional communication and collaboration tools and
social media for communi-
cation, collaboration, cooperation, and connection.
�■ An extensively revised chapter—Chapter 6, “Enhancing
Business Intelligence Using Big
Data and Analytics”—provides extended coverage on business
intelligence and advanced

analytics and greatly expanded content on machine learning,
predictive modeling, artificial
intelligence, unstructured data analytics, and spatial decision
support.
�■ A revised chapter—Chapter 8, “Strengthening Business-to-
Business Relationships via
Supply Chain and Customer Relationship Management” —
provides updated content
on business-to-business electronic commerce and supply chain
management as well as
customer relationship management (CRM).
�■ A revised chapter—Chapter 9, “Developing and Acquiring
Information Systems”—
provides updates to various topics and extended content on
alternative system development
methodologies.
�■ A revised chapter—Chapter 10, “Securing Information
Systems”—provides an update to
all topics and deeper coverage on industrial espionage and
cyberterrorism.
�■ A revised Technology Briefing covers foundational concepts
related to various informa-
tion technologies. The Technology Briefing provides the
foundations for a deeper under-
standing of the topics introduced in Chapter 3 and is intended
for use in more technically
oriented courses. Each section of this briefing was designed to
stand alone—it can be read
with or without the other sections.
In addition to the changes within the main chapter content, we
have also added two new

features to each chapter—Green IT and Security Matters. Green
IT presents environmental issues
arising from the use of information systems. For example, in
Chapter 4, we discuss the environ-
mental impacts of online shopping. Security Matters presents
some current issues and threats
arising from the ubiquitous use of information systems. For
example, in Chapter 5, we discuss
how hacktivists challenged the extramarital dating website
Ashley Madison.
Beyond the chapter content and features, we have also made
substantial changes and refine-
ments to the end of each chapter. In particular, we carefully
revised many of the end-of-chapter
problems and exercises to reflect content changes and new
material. Further, we have carefully
updated the end-of-chapter cases about contemporary
organizations and issues to illustrate the
complexities of the digital world. Each case mirrors the primary
content of its chapter to better
emphasize its relevancy within the context of a real
organization. All these elements are discussed
more thoroughly next.
PREFACE xxi
Our goal has always been to provide only the information that is
relevant to all business
students, nothing more and nothing less. We believe that we
have again achieved this goal with
Information Systems Today, Eighth Edition. We hope you

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