L6 - Xerophytes and Hydrophytes

What are xerophytes?

Plants that are adapted to live in dry areas.

e.g. conifers. mariam grass, cacti.

Adaptions of xerphytes?

• thick waxy cuticle

• sunken stomata - control microclimates

• reduced number of stomata - reduced water loss

• reduced number of leaves - less surface area to lose water

• hairy leaves - reduce air movement to increase humidity

• succulents - specialised water stores in parenchyma and roots

• loss of leaves in dry seasons

• long + deep roots that spread in an area to catch water

• When die they leave behind seeds to germinate when rain falls.

How does sunken stomata control microclimates?

The sunken stomata creates a tiny space where water is not blown away, creating a humid microclimate. Water potential in and out of leaf is kept high.

What are Hydrophytes?

Plants that live in water - submerged on the surface.

e.g. water lilies, water cress, duckweeds, marginals

Adaptions of Hydrophytes?

• Very thin, no waxy cuticle (no need to conserve water)

• Loads of stomata that stay open with inactive guard cells

• stomata on upper surface of floating plants - contact with air

• Wide flat surface to capture as much light

• small roots - water directly diffuses into stem + leaves

• air sacs for leaves to float

• aerenchyma (specialised parenchyma) - large air spaces formed from apoptosis (programmed cell death)

  • allows leaves to be buoyant