Slide1 : 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) Visit www.worldofteaching.com
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Slide2 : 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
Slide3 : 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.
Slide4 : XEROPHYTES
Slide5 : 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
Slide6 : 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;
Slide7 : Xerophyte adaptations summary:
Slide8 : All Cacti are xerophytes
Slide9 : 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.
Slide10 : Transverse Section Through Leaf of Xerophytic Plant
Slide11 : XEROPHYTE
SPECIES STUDY:
MARRAM GRASS
Slide12 : Marram grass possesses: rolled leaves, leaf hairs and sunken stomata. These adaptations make it resistant to dry conditions and of course sand-dunes which drain very quickly retain very little water.
Slide18 : BYB3 June 2001 Question 8 part c
Slide19 : BYB3 June 2001 Question 8 part c
ANSWERS
Slide20 : BYB3 Jan 2002 Question 6 part c
Slide21 : BYB3 Jan 2002 Question 6 part c
ANSWERS