2. Plant Growth: an irreversible change in the size of a cell, organ or
whole organism.
Differentiation: Cells taking on specialized form and function.
Plant Development: the orderly and progressive change from seed
germination through juvenility, maturity, flowering and fruiting.
7. Male and Female Gametophyte
Gametophyte – embryo sac
Gametophyte – anther
Gamete – egg
Gamete – two sperm cells (in pollen grain or tube)
Male
Female
17. Simplified Structure of A Mature Seed
Seed coat
Embryo
Endosperm
Seed coat is dead tissue.
It protects everything
inside it.
Embryo is a minute
plant .
Endosperm provides energy
for seed germination and
early seedling growth.
18. (1) How is a seed formed?
(2) How does a seed become a seedling?
(3) How is shoot formed?
(4) How is root formed?
(5) How is a flower formed?
19. Dry seeds Imbibed seeds
Water Uptake: the First Event in Germination
35. From: PM Ray, “The Living Plant”
Apical dominance is a
phenomenon in which the
apical bud tends to
“dominate” stem growth in
the sense that all of the
axillary buds immediately
below it do not grow out to
form branches. Thus the
stem grows tall, not wasting
resources by growing wide.
The idea is that auxin
produced in the apical bud is
transported down the stem
and suppresses the
outgrowth of the lateral
(axillary) buds. If the tip is
cut off the auxin source is
removed and the buds begin
to develop into branches.
36. (1) How is a seed formed?
(2) How does a seed become a seedling?
(3) How is shoot formed?
(4) How is root formed?
(5) How is a flower formed?
37. Root Systems
Taproot system: characterized by
having one main root (the taproot)
from which smaller branch roots
emerge. When a seed germinates,
the first root to emerge is the radicle,
or primary root. In conifers and
most dicots, this radicle develops
into the taproot.
Fibrous root system: characterized by
having a mass of similarly sized roots. The
radicle from a germinating seed is short lived
and is replaced by adventitious roots.
Adventitious roots are roots that form on
plant organs other than roots. Most monocots
have fibrous root systems.
38. Root tip has 4 developmental zones
Root cap: Protects RAM and push
Meristematic zone: Primary root
Elongation zone: Rapid cell
elongation, rate of division
decreases with distance from
meristem
Maturation zone: Cells get their
mature differentiated features.
No lateral organs produced from apical
meristem to avoid hindrance in soil
penetration
Branch roots arise from non
growing region
Root System development
39. Cells of the root epidermis develop projections called root hairs. These
elongate by “tip growth” and increase surface area for water and mineral
uptake. Root hairs are found away from the root tip, in the region of
maturation.
Note that the root hair develops as an
outgrowth from individual epidermal
cells; that is, the root hair is not a cell
separate from the epidermal cell. The
Figure shows (bottom to top) four
stages of root hair development: cell
specification, root hair initiation, tip
growth, and maturation.
40. (1) How is a seed formed?
(2) How does a seed become a seedling?
(3) How is shoot formed?
(4) How is root formed?
(5) How is a flower formed?
42. Internal factors
Phase change
Hormones
External factors
Light
Temperature
Total light radiation
Water availability
Cues for Flower Evocation
Flower Evocation: The events occurring in the shoot apex that
specifically commit the apical meristem to produce flowers.
45. Three Types of Genes Control Floral Identify
1. Gene A activity controls the first and second whorls
2. Gene B activity controls the second and third whorls
3. Gene C activity controls the third and fourth whorls.
46. ABC Model for Flower Development
Taiz and Zeiger, Plant Physiology
