1. Basic attributes
common to many forms of life
Cellular structure and intracellular
compartmentalization; and
Metabolism and transfer of energy
Storage and transmission of genetic information
Reproduction
Development- each individual will go through
certain changes of form and function during
its life
2. A After a corn grain (seed) germinates, its
radicle and coleoptile emerge. The radicle
develops into the primary root. The
coleoptile grows upward and opens a
channel through the soil to the surface,
B The plumule develops into the seedling’s
primary shoot, which pushes through the
coleoptile and begins photosynthesis. In corn
plants, adventitious roots that develop from the
stem afford additional support for the rapidly
growing plant.
Fig. 31-3, p. 525
Stepped Art
hypocotyl
radicle
branch
root
branch
root
primary
root
primary root
adventitious
(prop) root
primary
leaf
coleoptile
coleoptile
coleoptile
4. Fig. 31-4a, p. 525
seed
coat radicle
cotyledons (two)
hypocotyl
primary root
A After a bean seed germinates, its radicle emerges
and bends in the shape of a hook. Sunlight causes the
hypocotyl to straighten, which pulls the cotyledons up
through the soil.
5. Fig. 31-4b, p. 525
primary
leaf
primary
leaf
withered
cotyledon
branch root
primary root
root nodule
B Photosynthetic cells in the cotyledons
make food for several days, then the
seedling’s leaves take over the task.
The cotyledons wither and fall off.
6. Fig. 31-22, p. 535
germination
mature
sporophyte
(2n)
zygote
in seed (2n)
fertilization
meiosis
in anther
meiosis
in ovary
DIPLOID
HAPLOID
microspores
(n)
megaspores
(n)
eggs (n) sperm (n)
male
gametophyte (n)
female
gametophyte (n)
7. Plant Development
• Plant development includes seed
germination and all events of the life cycle,
such as root and shoot development,
flowering, fruit formation, and dormancy
• These activities have a genetic basis, but
are also influenced by environmental
factors
10. Development- process – complex,
multicellular organism arises from a single
cell, a gradual process, so the complexity
of the embryo increases progressively.
Development –progressive-i.e. a simple
embryo with few cell types organized in a
crude pattern gradually refined to
generate a complex organism with many
cell types showing highly detailed
organization.
11.
12. Development- process by which an
organism changes to acquire new
structures and abilities. It occurs in
response to various levels of control:
1. Genetic instructions
2. Intercellular interaction
3. Environmental factors
14. Growth
: increase of size and weight,.
Diameter, height, volume and weight can
be measured.
Biochemical properties can also be
established:
Enzyme activity, pigment content,
protein content, DNA and RNA content may
be used to characterize the organism.
Single cells show 2 major components of
growth: division and enlargement
15. After imbibition of water by
seeds, the growth by which
the embryo becomes a young
seedling occurs by both
expansion of cells originally
present in the dormant embryo
and mitotic divisions resulting in
an increase in cell number
18. The plane in which a cell divides is
determined during late interphase.
First sign of this spatial
orientation is rearrangement
of the cytoskeleton In the
cytoplasm into a ring called
pre-prophase band. Band
disappears before
metaphase but it predicts the
future plane of division. It
predicts where the cell plate
will be inserted (the division
site).
The “imprint” consist of actin
microfilaments that remain
after microtubules disperse.
19. Fig. 35-25
of
ivision
s of cell division
Developing
guard cells
Guard cell
“mother cell”
ecialized
rmal cell
etrical cell division
If planes of division of the
descendants are parallel
to the plane of the ist cell
division, single file of cells
results.
Cell division in 3 planes
gives rise to a cube. If
planes vary randomly,
will be a disorganized
clump.
Guard cells
form
perpendicular
to the
first division
21. Cell expansion contributes to plant form.
Orientation of cell growth is in the plane
perpendicular to the orientation of the cellulose
microfibrils in the wall. Enzymes weaken cross-
links in the wall, and allow it to expand as water
diffuses into vacuole by osmosis.
22. The orientation of cellulose microfibrils (CMFs) is
a determining factor in cell growth. Elongation is
favored when CMFs are oriented transversely to
the direction of growth while elongation
is limited when CMFs are oriented in the oblique
or longitudinal direction.
Orientation of cellulose microfibrils in growth-
cell expansion. CA 80 CELLULOSE IN A MICROFIBRIL
23. Auxins in cell expansion
ENZYME THAT BREAKS CROSS LINKS
OR HYDROGEN BONDS BETWEEN
CELLULOSE MICROFIBRILS
25. Cell Differentiation
Cells become specialized in structure
and function. A fertilized egg gives rise
to many different kinds of cells, each
with a different structure and function.
A program of differential gene
expression (the expression of
different sets of genes by cells with
the same genome) leads to the
different cell types in a multicellular
organism
26.
27. Gene expression
Cells must continually turn genes on and off
in response to signals from external and
internal environment.
Regulation of gene expression is necessary
for cell specialization in multicellular
organisms.
The differences between cell types are not
due to different genes being present but to
differential gene expression, the expression of
different sets of genes by cells with the same
genome
28. DNA
Primary RNA
transcript
protein
inactive mRNA
Inactive protein
mRNA degradation
control
Translational control
by ribosome selection
among mRNAs
Protein activity
control
Transcriptional
control
1
2 Processing
control
3 Transport
control
mRNA
mRNA
6
4 5
Steps at which
gene expression
can be controlled
in eukaryotes
NUCLEUS
CYTOPLASM
29. Each stage is a
potential
control point at
which gene
expression can
be turned on or
off, accelerated
or slowed down.
In all organisms,
a common
control point for
gene expression
is at transcription
. In this stage regulation is often
in response to signals coming
from outside cell e.g. hormones
or other signaling molecules.
31. Pattern structure
Form –one of outstanding characteristics of living
organisms.
Though complex,various parts bear predictable,
repeated relations to one another.
Regularity or deviation from random distribution of
various parts of cells or tissues
32. O X O
O X O
O X O
The distribution of the specialized cell is not
random since the location of any given cell is at
least predictable from the location of other cells
B
X O
X O
X O
X O
X X
X X O O
X x O O
O O
C
D
Non-random
Non-random
Non-random
33. O X O
X
X O
O X
O X O
O X O
O X O
A
B
X O
X O
X O
X O
X X
X X O O
X x O O
O O
C
D
random
Non-random
Non-random
Non-random
34. Pattern formation-
Development of a spatial organization in which the tissues and
organs are all in their characteristic places.
It is the development of specific structures in specific locations.
Cells must be organized into multicellular arrangements of
tissue and organs.
Pattern formation is determined by positional information in the
form of signals that continuously indicate to each cell its
location within a developing structure
Each cell within a developing organ responds to positional
information from neighbouring cells by differentiating into a
particular cell type, oriented in a particular way.
- gradients of specific molecules
- hormones, proteins
-mRNA provide positional information
35. Pattern formation
First patterning event in the embryo- axis
specification. This reflects asymmetric
division of the zygote:
apical cell
basal cell
Establishment of the principal body axis
--ANTEROPOSTERIOR
--DORSOVENTRAL
embryo
Suspensor filament
41. Morphogenesis- creation of form
Physical process that give an organism its shape
in each cell type
The different kinds of cells not randomly
distributed but organized into tissues and organs in
a particular three- dimensional arrangement.
Reflects different aspects of cell structure and behavior
including: cell division, cell shape and size, interaction
between cells , and cell death.
42. In animals,
morphogenesis
– many involve
movement of
cells relative to
other cells
In plants, cells have cell walls
and middle lamella which
tightly cement cells together.
No relative cell movement or
migration.
Morphogenesis reflects a
restricted set of processes-
such as:
1.differential rates and
planes of cell division
2. changes in cell size
due to the increasing volume
of the vacuole.
43. Planes of cell division determine shape of
particular tissues.
Terms to describe planes of cell division:
anticlinal – SURFACE GROWTH.
occur in the plane of the sheet- expands
the sheet WITHOUT INCREASING THE
THICKNESS.
periclinal- occur at right angles to the
plane of a sheet so results in its expansion
into multiple layers.
Switching from anticlinal to periclinal cell
division is critical for some morphogenetic
processes, e.g. outgrowth of leaves.
44. Model organisms
Uses:
• to gain comprehensive knowledge about a
complete plant.
• to further detailed understanding of
mechanisms and processes in plants.
• to understand particular biological phenomena
with the expectation that discoveries made on
the model organism will provide insight into the
workings of other organisms
Select model organism that lend themselves to
study of a particular group and are
representative of a larger group.
46. Arabidopsis thaliana (wall cress)
Small, less than 30 cm
Life cycle-about 6-8 weeks, hermaphrodite
flowers, self-fertilizing flowers.
Easy to grow large numbers in the lab. Under
continuous light 25 degrees centigrade, up
to 10,000 to 50,000 seeds. Plants can grow
to form ripe seeds within 8 weeks
A single flower can produce 30-50 seeds.
Whole plant can produce several thousands, up
to 10,000 seeds per plant making study of
genetics easier.
Ideal for isolating mutants and for genetic
47. 2n=10, have 26,700 protein-encoding
genes but many are duplicates, ca 15,000
different types of genes,
It has one of the smallest genomes in
the plant kingdom: 115,409,949 base pairs
of DNA distributed in 5 chromosomes (2n
= 10).
Very little "junk" DNA
48. Transgenic plants can be made easily using Agrobacterium
tumefaciens as the vector to introduce foreign genes.
Mutations can be easily generated (e.g., by irradiating the
seeds or treating them with mutagenic chemicals).
It is normally self-pollinated so recessive mutations quickly
become homozygous and is expressed
49. Aim is to to establish a
blueprint for how plants
develop
50. inflorescences
• 2n=20, 10 large chromosome pairs
•Large no of progeny per cross ca 100 to 200 )
•Facilitated discovery of transposons (jumping genes)-mobile
genetic elements that disrupt the functions of some genes.
51.
52. Levels of developmental control
1. Genetic and intracellular control of
development.
An individual mature cell in the vegetative
body of the plant retains within nucleus all
the genetic information to reproduce the
dev. steps necessary to form the whole
organism.
Genetic constitution is expressed in terms
of the biochemical events within the cell
which lead to specific cell differentiation at
specific times.
57. Levels of developmental control
2. Hormonal and intercellular control of
development
A hormone may act by altering gene
expression
affect activity of existing enzymes
changing properties of membrane
Any of the above could redirect the
metabolism and development of a cell
responding to small number of molecules
63. MAIN Factor that affects
color is soil pH.
Acidic= pink/red flowers
Alkaline= blue flowers
Environmental factors
64. Etiolated shoot in potato –developing in the absence of light, turn
green upon exposure to light. The plant is able to detect the light
intensity and wavelength by using photoreceptors , but receptor
does not interact directly with the cell’s DNA but a signal
transduction chain is involved:phytochrome, blue light/UV-A
and UV-B receptors .
Editor's Notes
Figure 31.3 Early growth of corn ( Zea mays ), a monocot.
Figure 31.4 Early growth of the common bean plant ( Phaseolus vulgaris ), a eudicot.
Figure 31.4 Early growth of the common bean plant ( Phaseolus vulgaris ), a eudicot.
Figure 31.22 Summary of development in the life cycle of a typical eudicot.
Figure 14.4 Base pairing during ( a ) DNA synthesis and ( b ) transcription.
