Plant Development

PS452

Feng ChenDepartment 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

Seedling

Mature plantsFlowering

Fruiting

Plant Life Cycle

(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?

(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

Gametophyte – embryo sac

Gametophyte – anther

Gamete – egg

Gamete – two sperm cells (in pollen grain or tube)

Male

Female

21-14

Anther

Tapetum(nutritive)Epidermis

Raven et al., 1999; Biology of Plants

Anther (lily)

Pollen sac Pollen mother cells(Microsporocytes)

Tetrad (n)

Free microspores (n)

Mature pollen (n)

Nucleus of vegetative cell

Generative cell

Pollen mother cell (Microsporocyte)(2n)

Meiosis

Pollen Development

“‘diploid’”

“‘haploid’”

Ovule Development

micropyle

funiculusouter integument

inner integument nucellus 20.8

Esau, 1977; Anatomy of Seed Plants

embryo sac

Megasporogenesis

(2n) (n) (n) (n)

Meiosis

Megasporocyte(mother cell)

“Megasporogenesis”

Egg Cell Differentiation

Buchanan et al., 2000’ Biochemistry and Molecular Biology of Plants

Haploid Egg

Antipodal cells

Egg cell

Synergid cells

Central nuclei

ovule

stigma

Pollen tube

Fertilization

Fertilization

Double Fertilization

Antipodal cells

Central nuclei

Egg cell

Synergid cell

Sperm nuclei Endosperm

Embryo

Figure 4.4

Embryogenesis

Simplified Structure of A Mature Seed

Seed coat

Embryo

Endosperm

Seed coat is dead tissue. It protects everything inside it.

Embryo is a minuteplant .

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?

Dry seeds Imbibed seeds

Water Uptake: the First Event in Germination

Bewley, Plant Cell

Events Occur during Seed Germination

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 DarkLight

Tomato Seed Anatomy

Endosperm

Seed coat

Embryo0.5 mm

Embryo

Endosperm

Embryo

Endosperm

Seed Coat Seed Coat

Embryo

Endosperm

Growth PotentialConstraint

Seed Coat

Involvement of Expansin Genes in Seed Germination

LeEXP4

Dissecting seed

LeEXP8

(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

CZ: central zone; PZ: peripheral zone; RZ: rib zone

Shoot Apical Meristem (SAM)

Taiz and Zeiger, Plant Physiology

Leaf Formation: Leaf Primordium

Figure 4.7

Leaf Anatomy

Taiz and Zeiger, Plant Physiology

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.

(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 tip has 4 developmental zonesRoot cap: Protects RAM and pushMeristematic zone: Primary rootElongation zone: Rapid cell elongation, rate of division decreases with distance from meristemMaturation 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

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

Internal factorsPhase change

Hormones

External factorsLight

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.

Vegetative SAM Reproductive SAM

Formation of Floral Meristems

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

Figure 4.8

Mutations in Floral Organ Identify Genes

Seed

Seedling

Mature plantsFlowering

Fruiting

Plant Life Cycle

(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?