Stomata & Guard Cells

I. Overview

• located in epidermis
• have chloroplasts
• found in stems, floral parts, fruits

II. Stomata: morphology

• Guard Cells
  • ellipitical
  • dumbbell shape (grasses)
• Subsidary cells
• radial micellation (walls)
  • thickened by pore
  • thin outer wall
• substomatal cavity
• found on upper, lower, or both (amhistomatous)
  • floating leaves:epistomatous
• 1% of leaf surface area

III. Physiology of stomata

• Opening/closing of stomata
• related to turgor pressure changes
• light receptors
  • Red
  • blue
  • cryptochrome: flavin molecule
  • compare blue vs red light
• Accumulation K+ ions in guard cells
• ATPase pump of H+
  • respiratory inhibitors (CN-)
  • no O2
  • shut down opening
• Counter ion
  • Cl- or malate 2-
• Evidence
  • no counter ion
  • pH drop
  • ion concentrations in subsidary cells

IV. Environmental Factors

• Light
• temperature
• Relative humidity
• carbon dioxide
• wind