PS452
Plant Development
Feng Chen
Department of Plant Sciences
University of Tennessee
01/21/2014
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.
Seed
(1) How is a seed formed?
(2) How does a seed
become a seedling?
Fruiting
Seedling
Plant Life Cycle
(3) How is shoot formed?
Flowering
(5) How is a flower
formed?
Mature plants
(4) How is root formed?
(1) How is a seed formed?
(2) How does a seed become a seedling?
(3) How is shoot is formed?
(4) How is root is formed?
(5) How is a flower formed?
Flower Structure
Figure 4.2
Male and Female Gametophyte
Male
Gametophyte – anther
Gamete – two sperm cells (in pollen grain or tube)
Female
Gametophyte – embryo sac
Gamete – egg
Anther
Pollen sac
Pollen mother cells
(Microsporocytes)
21-14
Anther
(lily)
Epidermis
Tapetum
(nutritive)
Raven et al., 1999; Biology of Plants
Pollen Development
Pollen mother cell (Microsporocyte)
(2n)
“‘diploid’”
Nucleus of
vegetative cell
Meiosis
Generative cell
Tetrad
(n)
Free microspores
(n)
Mature pollen
(n)
“‘haploid’”
Ovule Development
outer
integument
funiculus
embryo
sac
inner
integument
nucellus
20.8
micropyle
Esau, 1977; Anatomy of Seed Plants
Megasporogenesis
Megasporocyte
(mother cell)
(2n)
(n)
(n)
Meiosis
“Megasporogenesis”
(n)
Egg Cell Differentiation
Buchanan et al., 2000’ Biochemistry and Molecular Biology of Plants
Haploid Egg
Antipodal cells
Central nuclei
Synergid
cells
Egg cell
Fertilization
stigma
Pollen tube
ovule
Fertilization
Double Fertilization
Antipodal cells
Central nuclei
Sperm nuclei
Endosperm
Egg cell
Embryo
Synergid cell
Embryogenesis
Figure 4.4
Simplified Structure of A Mature Seed
Seed coat
Seed coat is dead tissue.
It protects everything
inside it.
Embryo
Embryo is a minute
plant .
Endosperm
Endosperm provides energy
for seed germination and
early seedling growth.
(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?
Water Uptake: the First Event in Germination
Dry seeds
Imbibed seeds
Events Occur during Seed Germination
Bewley, Plant Cell
Water Relations and Seed Germination
High water availability
Medium water availability
Low water availability
Temperature and Seed Germination
Some Seeds Require Light for Germination
Dark
Light
Dark
Tomato Seed Anatomy
Seed coat
0.5 mm
Endosperm
Embryo
Embryo
Embryo
Endosperm
Endosperm
Seed Coat
Seed Coat
Constraint
Growth Potential
Embryo
Endosperm
Seed Coat
Involvement of Expansin Genes in Seed Germination
LeEXP4
LeEXP8
Dissecting seed
(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?
Figure 4.1
Formation of SAM
Taiz and Zeiger, Plant Physiology
Shoot Apical Meristem (SAM)
CZ: central zone; PZ: peripheral zone; RZ: rib zone
Taiz and Zeiger, Plant Physiology
Leaf Formation: Leaf Primordium
Figure 4.7
Leaf Anatomy
Taiz and Zeiger, Plant Physiology
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.
From: PM Ray, “The Living Plant”
(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?
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.
Root System development
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
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.
(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?
Flower Structure
Cues for Flower Evocation
Flower Evocation: The events occurring in the shoot apex that
specifically commit the apical meristem to produce flowers.
Internal factors
Phase change
Hormones
External factors
Light
Temperature
Total light radiation
Water availability
Formation of Floral Meristems
Vegetative SAM
Reproductive SAM
Genetic Control of Flower Development
Taiz and Zeiger, Plant Physiology
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.
ABC Model for Flower Development
Taiz and Zeiger, Plant Physiology
Mutations in Floral Organ Identify Genes
Figure 4.8
Seed
(1) How is a seed formed?
(2) How does a seed
become a seedling?
Fruiting
Seedling
Plant Life Cycle
(3) How is shoot formed?
Flowering
(5) How is a flower
formed?
Mature plants
(4) How is root formed?