Xerophytes

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Slide 1

Aims of the session:

Take measurements of leaves + see if xerophytes have a different pattern of mass loss

Learn about the adaptations xerophytes have

See what type of question they can ask about xerophytes (and be able to answer it)

Slide 2

Plant adaptations to habitats

Plants in different habitats possess different adaptations:

Mesophytes: plants adapted to a habitat with adequate water

Xerophytes: plants adapted to a dry habitat

Halophytes: plants adapted to a salty habitat

Hydrophytes: plants adapted to a freshwater habitat

Slide 3

Hydrophyte

Leaf undersurface of the tree fern. Extremely high number of stomata per unit in a species living in tropic cloud forests where is is very moist.

Slide 4

Xerophytes

Slide 5

Stomata sunken in pits creates local humidity/decreases exposure to air currents;

Presence of hairs creates local humidity next to leaf/decreases exposure to air currents by reducing flow around stomata;

Thick waxy cuticle makes more waterproof impermeable to water;

Xerophytes possess some or all of these adaptations to prevent excessive water loss

Slide 6

Xerophytes possess some or all of these adaptations to prevent excessive water loss cont.

Stomata on inside of rolled leaf creates local humidity/decreases exposure to air currents because water vapour evaporates into air space rather than atmosphere e.g. British Marram grass

Fewer stomata decreases transpiration as this is where water is lost;

Slide 7

Xerophyte adaptations summary:

Slide 8

All Cacti are xerophytes

Slide 9

Left and right Epidermis of the cactus Rhipsalis dissimilis.

Left: View of the epidermis surface. The crater-shaped depressions with a guard cell each at their base can be seen.

Right: X-section through the epidermis & underlying tissues. The guard cells are countersunk, the cuticle is thickened. These are classic xerophyte adaptations.

Slide 10

Transverse Section Through Leaf of Xerophytic Plant

Slide 11