1. Plant Development PS452 Feng Chen 01/21/2014
Department of Plant Sciences
University of Tennessee
01/21/2014

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.

3. (2) How does a seed (1) How is a seed formed? become a seedling?
(3) How is shoot formed?
(4) How is root formed?
(5) How is a flower
formed?
Fruiting
Seedling
Plant Life Cycle
Flowering
Mature plants

4. (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?

5. Flower Structure

6. Figure 4.2

7. Male and Female Gametophyte
Gametophyte – anther
Gamete – two sperm cells (in pollen grain or tube)
Female
Gametophyte – embryo sac
Gamete – egg

8. Anther Pollen mother cells Pollen sac (Microsporocytes) Tapetum 21-14
(nutritive)
Anther
(lily)
Epidermis
Raven et al., 1999; Biology of Plants

9. Pollen mother cell (Microsporocyte) Nucleus of vegetative cell
Pollen Development
Pollen mother cell (Microsporocyte)
(2n)
“‘diploid’”
Meiosis
Nucleus of vegetative cell
Generative cell
Tetrad
(n)
Free microspores
(n)
Mature pollen
(n)
“‘haploid’”

10. Ovule Development outer funiculus integument embryo sac inner
20.8
embryo
sac
inner
integument
nucellus
micropyle
Esau, 1977; Anatomy of Seed Plants

11. Megasporogenesis “Megasporogenesis” Megasporocyte (mother cell) (2n)
Meiosis
“Megasporogenesis”

12. Egg Cell Differentiation
Buchanan et al., 2000’ Biochemistry and Molecular Biology of Plants

13. Haploid Egg
Antipodal cells
Central nuclei
Synergid
cells
Egg cell

14. Fertilization Fertilization
stigma
Pollen tube
ovule
Fertilization

15. Double Fertilization Antipodal cells Central nuclei Sperm nuclei
Endosperm
Egg cell
Embryo
Synergid cell

16. Embryogenesis
Figure 4.4

17. 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.

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. Water Uptake: the First Event in Germination
Dry seeds
Imbibed seeds

20. Events Occur during Seed Germination
Two purposes:
Bewley, Plant Cell

21. Water Relations and Seed Germination
High water availability
Medium water availability
Low water availability

22. Temperature and Seed Germination

23. Some Seeds Require Light for Germination
Dark
Dark

24. Tomato Seed Anatomy
Seed coat
0.5 mm
Endosperm
Embryo

25. Embryo
Embryo
Endosperm
Endosperm
Seed Coat
Seed Coat

26. Embryo Endosperm Seed Coat
Constraint
Growth Potential
Embryo
Endosperm
Seed Coat

27. Involvement of Expansin Genes in Seed Germination
LeEXP4
LeEXP8
Dissecting seed

28. (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?

29. Figure 4.1

30. Formation of SAM
Taiz and Zeiger, Plant Physiology

31. Shoot Apical Meristem (SAM)
CZ: central zone; PZ: peripheral zone; RZ: rib zone
Taiz and Zeiger, Plant Physiology

32. Leaf Formation: Leaf Primordium

33. Figure 4.7

34. Leaf Anatomy
Taiz and Zeiger, Plant Physiology

35. 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”

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 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

39. Cells of the root epidermis develop projections called root hairs
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?

41. Flower Structure

42. 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

43. Formation of Floral Meristems
Vegetative SAM
Reproductive SAM

44. Genetic Control of Flower Development
Taiz and Zeiger, Plant Physiology

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

49. Mutations in Floral Organ Identify Genes
Figure 4.8

50. (2) How does a seed (1) How is a seed formed? become a seedling?
(3) How is shoot formed?
(4) How is root formed?
(5) How is a flower
formed?
Fruiting
Seedling
Plant Life Cycle
Flowering
Mature plants