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Plant Development

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Plant Development

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  1. PS452 Plant Development Feng Chen 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 become a seedling? (1) How is a seed formed? (3) How is shoot formed? (4) How is root formed? (5) How is a flower formed? Seed 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 Male Gametophyte – anther Gamete – two sperm cells (in pollen grain or tube) Female Gametophyte – embryo sac Gamete – egg

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

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

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

  11. Megasporogenesis Megasporocyte (mother cell) (n) (n) (2n) (n) 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 stigma Pollen tube ovule Fertilization

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

  24. Tomato Seed Anatomy Seed coat Endosperm 0.5 mm Embryo

  25. Embryo Embryo Endosperm Endosperm Seed Coat Seed Coat

  26. Growth Potential Constraint 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. 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

  47. Mutations in Floral Organ Identify Genes Figure 4.8

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