Plant Physiology

A. Transport

  1. Two main issues for a plant:
    1. Water and minerals must go up
    2. Sap (glucose) must go down  - or up (early spring)!
  2. Hypotheses:
    1. Water moves up the stem by diffusion or capillary action 
    2. Water moves up the stem by positive (root) pressure 
    3. Water moves up the stem by negative pressure (suction)
  3. Mechanisms of water transport
    1. Root pressure:
    2. Transpiration:
  4. Mechanisms of phloem transport
    1. Source and sink principle
    2. Phloem loading & unloading
      • active transport
    3. Bulk flow

B. Hormonal regulation

  1. Auxins
    1. Cell elongation
    2. Secondary growth
    3. Fruit development
      • source: seed 
  2. Cytokinins
    1. Cell division
    2. Differentiation
  3. Gibberellins 
    1. Seed germination
    2. Spring bud growth
    3. Cell elongation & Cell division
  4. Abscisic Acid
    1. Growth inhibition in buds, meristems, seeds
    2. Stress response
  5. Ethylene
    1. Fruit ripening
    2. Leaf abscission

C. Response to the environment

  1. Gravitropism: gravity sensors (statoliths)
  2. Phototropism: light receptors (e.g. phytochromes)
  3. Thigmotropism: touch receptors
  4. Turgor movements
  5. Circadian rhythms
  6. Photoperiodism: red light receptors (phytochrome)

D. Reproduction

  1. Review: Life cycle/Alternation of Generations
  2. Flower: Reproductive organ system
    1. Sepals - modified leaves 
    2. Petals - modified leaves 
    3. Stamen = Anther + Filament
    4. Carpel = Ovary + Style + Stigma
    5. Complete vs. Incomplete flowers (Grass)
    6. Perfect vs. imperfect flowers (Corn)
    7. Monoecious vs. dioecious (Date palm)
  3. Gametophyte development
    1. Male gametophyte
      • pollen sac microsporocytes meiosis 4 microspores (N) pollen grain 2 sperm cells (N)
    2. Female gametophyte
      • ovule megasporocytes meiosis 1 megaspore (N) embryo sac egg (N) 
  4. Pollination
    1. Pollen transfer
    2. Avoiding self-pollination
      • dioecius plants
      • stamen + anther development
      • anatomical separation
      • biochemical incompatibility
  5. Fertilization
    1. Pollen tube grows into stigma, style
    2. Double fertilization
      • 1 sperm fertilizes egg = 2N embryo
      • 1 sperm fertilizes 2N central cell = 3N cell = endosperm
  6. Fate of the flower
    1. Sepals, petals, stamen:
      • degenerate (pea)
      • become part of fruit (apple)
    2. Ovary Fruit
      • simple fruit (cherry) 
      • aggregate fruit (blackberry): >1 ovary/flower
      • multiple fruit (pineapple): >1 flower
    3. Ovule seed