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Xerophyte adaptations to reduce water loss


Jonny Hall

on 11 December 2011

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Transcript of Xerophyte adaptations to reduce water loss

Xerophytes General Factors of living in ARID conditions Both textbook's love this:
Marram Grass
and their adaptations If water loss is greater than water uptake, plants lose their turgidity and plants lose structure (wilt) and the plant will die.

Xerophytes are plants that have a number of adaptations to prevent water loss. What are the factors that contribute to preventing water loss? Opuntia=Cactus Flattened, photosynthetic stems that store water Spine like leaves, reducing the surface area and protection from animals One of the few plants that can survive in mobile sand dunes; very dry conditions. The leaves can roll up, exposing a tough waterproof cuticle Stomata are found deep in pits of the. Water has to diffuse a long way before it reaches air, slowing water loss. Hinge cells cause the opening and the closing of the marram grass in response to air humidity. Leaf rolling traps air inside the rolled leaf and the air can remain humid. Hairs on the cell keep the humid air trapped inside the rolled leaf.
When the leaf is unrolled, the hairs again help to trap a layer of moist air close to the leaf surface reducing air movement and increasing the layer of thicknes, AS WELL as keeping humid air at the surface. Summary:
-Stomata deep in pits
-Hinge cells
-Leaf rolling traps
-Hairs on the cell keep humid air inside the rolled leaf Leaves with small surface area- pine needles are a prime example. Reduces amount of water lost by transpiration Densely packed spongy mesophyll. Reduces the cell surface area that is exposed to the air inside the leaves, meaning less water will evaporate. Hairs trap a layer of air close to the surface, where it becomes saturated, reducing the water vapour potential gradient, reducing water loss. Closing the stomata when water availability is low reduces water loss and therefore reduce need to take up water. Pits containing stomata at their base help to reduce water loss because of changing the water vapour potential gradient when the base traps air (that's later saturated with water vapour) Mesophyll Layer
(I think) Rolling the leaves so that the lower epidermis isn't exposed to the atmosphere, and can trap air that is saturated. Reduces transpiration as you should know (Little Steve Can't Lift The Heavily Weighted Webcam) In Summary... -Xerophytes are plants in extreme conditions...
-Marram Grass has : 1)rolled up leaf to trap air 2)thick waxy cuticle 3)Hairs to reduce water movement
-In general, remember a roll up leaf keeps gases for plant functions or to later reduce the WV potential gradient to reduce water lost.
-High concentration of salts in the cells to reduce water potential gradient
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