Biology B3 - Plants and Transpiration

Leaves

Leaves are designed for making food.

• The waxy cuticle stops it losing water and drying out
• The palisade cells contain the most chloroplasts. They are long to maximize the chance of the light hitting them and although you cant see it on this diagram they have spaces to allow gas diffusion - increase surface area (Carbon dioxide in, oxygen out)
• The vascular bundle (also know as the leaf vein) contain the xylem and phloem (Phloem = Food). These cover all the leaf and bring water, while taking away the glucose created in photosynthesis.
• The stomata are tiny pores which let carbon dioxide in, and oxygen and water vapour out. However, if the water supply they close automatically so the plant doesn’t dry up.
• The guard cells actually close the stomata. Open = Turgid --- Closed = Flaccid. While this stops loss of water vapour by transpiration, it also stops photosynthesis.
• The leaf is very thin which minimises the distances which carbon dioxide has to travel
• They are also arranged in the best way for absorbing the maximum amount of light energy without blocking out the light for other leaves

The shape of the leaf also aids it.

• The leaf is very thin which minimises the distances which carbon dioxide has to travel by diffusion
• Becuase it is thin and flat, it has a increased surface area

Transpiration

Transpiration – The loss of water from a plant through evaporation

Advantages -

• This creates a slight shortage of water in the leaf which draws more water up…