Xerophytes + Hydrophytes

• Hydrophyte

  • Issue of water-logging, air spaces need to be full of air, not water; helps plants float on surface for more light
  • Adaptations:
  • Thin to no waxy cuticle
  • Floating leaves, due to spaces
  • Large + thin
  • Upper surface stomata in contact with air, many always open
  • No support structures; water supports
  • Smaller roots, less uptake needed
  • Elongated petioles/leaf stalks
  • Aerial flowers
  • Poor xylem
  • Little to no lignin in vascular bundles
  • Few sclereids or fibres
  • Arenchyma:
  • Spongy tissue in roots, leaves + stems
  • Filled w/ O_2 from photosynthesis
  • Help buoyancy
  • Low-resistant O_2 pathway to diffuse to tissue below water
  • Pneumatophores:
  • Roots water-logged
  • Air short supply
  • Special aerial roots w/ lenticels + raised pores; let gases into roots
• Xerophyte

  • Thick waxy cuticle
  • Rolled leaves
  • Reduces air exposure
  • Stomata on inside
  • Inc water vapour in roll + humid air near stomata
  • Hairy leaves
  • Trap saturated air layer
  • Reduced area
  • Some plants lose leaves if water unavailable
  • Sunken stomata
  • Stomatal hair, trichores, keep humid air
  • Low stomata density, smaller SA
  • Extensive roots; max water uptake
  • Succulents
  • Water in specialised stem + root tissues
  • Inc water vapour near stomata reduces WP gradient; slows water loss
  • Marram Grass:
  • Rolled leaves w/ sunken stomata in
  • Trichomes trap water vapour
  • Water evaporated via stomata collects in rolled leaf
  • Reduces WP gradient + water loss