7. Alternation of Generations
Life cycle involves alternation of generations
Sporophyte (2n):
Multicellular individual that produces spores by
meiosis
Spores is haploid cell that will become gametophyte
Gametophyte (1n):
Multicellular individual that produces the gametes
Gametes fuse in fertilization to form zygote
Zygote is a diploid cell that becomes a s
sporophyte
7
9. Other Terrestrial Adaptations
Vascular tissue transports water and nutrients to the
body of the plant
Cuticle provides an effective barrier to water loss
Stomata bordered by guard cells that regulate
opening, and thus water loss
9
10. Nonvascular Plants: Bryophytes
Nonvascular plants (bryophytes)
Lack specialized means of transporting water and
organic nutrients
Do not have true roots, stems, and leaves
Dependent sporophyte consists of a foot, stalk and
sporangium
Gametophyte is dominant generation
Produce eggs in archegonia
Produce sperm in antheridia
Sperm swim to egg in
film of water to make
zygote
10
11. Nonvascular Plants
Hornworts (phlym Anthocerophyta) have small
sporophytes that carry on photosynthesis
Liverworts (phylum Hepatophyta) have either
flattened thallus or leafy appearance
Mosses (phylum Bryophyta) usually have a leafy
shoot, although some are secondarily flattened
Can reproduce asexually by fragmentation
11
13. Seedless Vascular Plants: Lycophyta
Club Mosses (phylum Lycophyta)
Typically, branching rhizome sends up short aerial
stems
Leaves are microphylls (have only one strands of
vascular tissue)
Most likely evolved as a simple side extensions of the
stem
Sporangia occur on surfaces of sporophylls
13
Grouped into club-shaped strobili
14. Seedless Vascular Plants
Roots evolved as lower extensions of the stem
today’s lychophytes, also called club mosses, include
three groups of 1,150 species:
o Ground pines (Lycopodium)
o Spike mosses (Selaginella)
o Quillwort (Iseotes)
14
15. Seedless Vascular Plants: Pteridophytes
Includes Ferns and their Allies (horsetails and
whisk ferns)
Have megaphylls (broad leaves)
allow plants to effectively collect solar energy
Produce more food and the possibility of producing more offspring
than plants without megaphylls
Horsetails
rhizome produces tall aerial stems
Contains whorls of slender, green branches
Small, scale like leaves also form whorl at the joint
15
16. Microphylls and Megaphylls
single strand of
vascular tissue
a. Microphyll
branched
vascular tissue
Megaphyll
One branch began to
dominate the stem system.
branched
stem system
b. Megaphyll evolution process
16
The side branches flattened
into a single plane.
Tissue filled in the spaces
between the side branches.
megaphyll
leaf
18. Figure 29.13-3
Key
Haploid (n)
Diploid (2n)
MEIOSIS
Spore
dispersal
Spore
(n)
Rhizoid
Underside
of mature
gametophyte
(n)
Sporangium
Sporangium
Antheridium
Young
gametophyte
Mature
sporophyte
(2n)
Sorus
New
sporophyte
Sperm
Archegonium
Egg
Zygote
(2n)
FERTILIZATION
Gametophyte
Fiddlehead (young leaf)
1 µm
In contrast with bryophytes, sporophytes
of seedless vascular plants are the
larger generation, as in familiar ferns
19. Seed Plants
Seed plants are the most plentiful plants in the
biosphere
Seed coat and stored food allow an embryo to survive
harsh conditions during long period of dormancy
Heterosporous
Drought-resistant pollen grains
Ovule develops into seed
19
20. Gymnosperms
Gymnosperms have ovules and seeds exposed on the surface of sporophylls
Conifers
Conifers, as well as other gymnosperm phyla, bear cones
Tough, needlelike leaves of pines conserve water with a thick cuticle and recessed stomata
Considered a “soft” wood because it consist primarily of xylem tissue (water flow)
Cycads
Large, finely divided leaves that grow in clusters at the top of the stem
Pollen and seed coats on separate plants
Ginkgoes
Dioecious: Some trees producing seeds and others producing pollen
Gnetophytes
20
None have archegonia
21. Figure 30.3-3
If a pollen grain germinates,
Immature
it gives rise to a pollen tube
ovulate cone that discharges sperm into
the female gametophyte
within the ovule
Female
gametophyte (n)
Integument (2n)
Spore wall
Micropyle
Pollen grain (n)
(a) Unfertilized ovule
Spore
wall
Egg nucleus
(n)
Megaspore (n)
Megasporangium
(2n)
Seed
coat
Discharged
sperm nucleus
(n)
Pollen tube
Male gametophyte (n)
(b) Fertilized ovule
Food
supply (n)
Embryo (2n)
(c) Gymnosperm seed
A seed is a sporophyte embryo, along with
its food supply, packaged in a protective
coat
22. Angiosperms
Ovules are always enclosed within diploid tissues
Two classes of flowering plants
22
Monocotyledones (Monocots) – 1 cotyledon
Eudicotyledones (Dicots) – 2 cotyledons
23. Monocots vs Eudicots
Number of cotyledons -- The cotyledons are the "seed leaves" produced by the embryo. They serve to
absorb nutrients packaged in the seed, until the seedling is able to produce its first true leaves and begin
photosynthesis.
The number of cotyledons found in the embryo is the actual basis for distinguishing the two classes
of angiosperms, and is the source of the names Monocots ("one cotyledon") and Eudicots ("two
cotyledons").
Number of flower parts -- Monocot flowers = divisible by three, usually three or six. Dicot flowers =
multiples of four or five
This character is not always reliable, however, and is not easy to use in some flowers with reduced
or numerous parts.
Leaf veins – Monocots = veins which run parallel the length of the leaf. Eudicots, = numerous veins
which reticulate between the major ones.
Stem vascular arrangement -- Vascular tissue occurs in long strands called vascular bundles. These
bundles are arranged within the stem of eudicots to form a cylinder, appearing as a ring of spots when
you cut across the stem. In monocots, these bundles appear scattered through the stem, with more of
the bundles located toward the stem periphery than in the center.
Root development -- In most eudicots (and gymnosperms) the root develops from the lower end of the
embryo, from a region known as the radicle. The radicle gives rise to an apical meristem which
continues to produce root tissue for much of the plant's life. By contrast, the radicle dies in monocots,
and new roots arise from nodes in the stem.
These roots may be called prop roots when they are clustered near the bottom of the stem.
Secondary growth – Gymnosperm and eudicots increase their diameter through secondary growth,
producing wood and bark. Monocots (and some dicots) do not produce wood.
26. The Flower
Peduncle (flower stalk) expands at tip into a receptacle
Bears sepals, petals, stamens, and carpels, all attached to receptacle in
whorls
Each stamen consists of an anther and a filament (stalk)
Carpel has three major regions
Ovary – swollen base
Style – elevates stigma
Stigma – sticky receptor of pollen grains
fruit
Calyx (collection of sepals) protects flower bud before it opens
Corolla (collection of petals)
26
29. Figure 30.2
PLANT GROUP
Mosses and other
nonvascular plants
Gametophyte Dominant
Sporophyte
Ferns and other seedless
vascular plants
Seed plants (gymnosperms and angiosperms)
Reduced, independent
(photosynthetic and
free-living)
Reduced (usually microscopic), dependent on surrounding
sporophyte tissue for nutrition
Reduced, dependent on
Dominant
gametophyte for nutrition
Dominant
Gymnosperm
Sporophyte
(2n)
Sporophyte
(2n)
Microscopic female
gametophytes (n) inside
ovulate cone
Gametophyte
(n)
Angiosperm
Microscopic
female
gametophytes
(n) inside
these parts
of flowers
Example
Gametophyte
(n)
Microscopic male
gametophytes (n)
inside pollen
cone
Sporophyte (2n)
Microscopic
male
gametophytes
(n) inside
these parts
of flowers
Sporophyte (2n)
32. Pearson – The Biology Place - http://www.phschool.com/science/biology_place/biocoach/plants/tissue.html
33. Ground Tissue
Parenchyma cells
–
–
–
–
–
Have thin and flexible primary walls
Lack secondary walls
Are the least specialized
Perform the most metabolic functions
Retain the ability to divided and diffrentiate
Collenchyma cells help support young parts of the plant shoot
They have thicker and uneven cell walls
The cells provide flexible support without restraining growth
Sclerenchyma cells are rigid because of thick secondary walls
strengthened with lignin
They are dead at functional maturity
There are two types:
1. Sclereids are short and irregular in shape and have thick
lignified secondary walls
2. Fibers are long and slender and arranged in threads
34.
35.
36. Roots
A root is an organ with important functions:
1. anchoring the plant
2. Absorbing minerals and water
3. Storing carbohydrates
In most plants, absorption of water and minerals
occurs near the root hairs, where vast numbers of
tiny root hairs increase the surface area
37. Figure 35.14
Epidermis
Cortex
Endodermis
Vascular
cylinder
100 µm
(a) Root with xylem and
phloem in the center
(typical of eudicots)
50 µm
Pericycle
Core of
parenchyma
cells
Xylem
Phloem
Endodermis
Pericycle
Xylem
Phloem
100 µm
(b) Root with parenchyma in the
center (typical of monocots)
Key
to labels
Dermal
Ground
Vascular
38. Figure 35.13
Cortex
Vascular cylinder
Epidermis
Root hair
Zone of
differentiation
Key
to labels
Dermal
Ground
Vascular
Zone of
elongation
Zone of cell
division
(including
apical
meristem)
Root cap
Mitotic
cells
100 µm
39. Most eudicots and gymnosperms have a taproot
system, which consists of:
A taproot, the main vertical root
Lateral roots, or branch roots, that arise from the taproot
Most monocots have a fibrous root system, which
consists of:
Adventitious roots that arise from the stems or leaves
Lateral roots that arise from adventitious roots
40. Stems
A stem is an organ consisting of
An alternating system of nodes, the point at which leaves are attached
Internodes, the stem segments between nodes
An axillary bud is a structure that has the potential to form a lateral
shoot, or branch
An apical bud, or terminal bud, is located near the shoot tip and
causes elongation of a young shoot
Apical dominance helps to maintain dormancy in most axillary buds
Many plants have modified stems (eg. Rhizoids, bulbs, stolons, tuber)
41. The vascular tissue of a stem or root is collectively
called the stele
In angiosperms the stele of the root is a solid
central vascular cylinder
The stele of stems and leaves is divided into
vascular bundles, strands of xylem and phloem
43. Seeds
Seed coat, or testa can be impenertrable, especially in long
dormancy need
Cotyledons are leaf-like structures in the seed that provide
nourishment while the seed germinates
Radicle = embryonic root
Plumule = seed shoot
Epicotyl = portion of stem above the point where the stem is
attached to the cotyledon
Hypocotyl = portion of stem below the cotyledon
Endosperm = source of nutrients
Hillum = point of attachment of seed to the ovary wall
Micropyle = small opening near hillum
44.
45.
46. Secondary growth increases the diameter of stems and
roots in woody plants
Secondary growth occurs in stems and roots of
woody plants but rarely in leaves
The secondary plant body consists of the tissues
produced by the vascular cambium and cork
cambium
Secondary growth is characteristic of gymnosperms
and many eudicots, but not monocots
47. Lateral meristems add thickness to woody plants,
a process called secondary growth
There are two lateral meristems: the vascular
cambium and the cork cambium
The vascular cambium adds layers of vascular
tissue called secondary xylem (wood) and secondary
phloem
The cork cambium replaces the epidermis with
periderm, which is thicker and tougher
