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?
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
Double Fertilization
Antipodal cells
Central nuclei
Egg cell
Synergid cell
Sperm nuclei Endosperm
Embryo
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?
Water Relations and Seed Germination
High water availability
Medium water availability
Low water availability
(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?
CZ: central zone; PZ: peripheral zone; RZ: rib zone
Shoot Apical Meristem (SAM)
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?
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.
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.