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Edexcel IGCSE Biology
What is the definition of transpiration?
loss of water vapour from the parts of the part above ground
How does loss of water occur?
through evaporation of water at the surfaces of the spongy mesophyll
diffusion of water vapour through the stomata
what do the many interconnecting air spaces between the mesophyll cells and stomata create?
large surface area which means evaporation can happen rapidly when the stomata are open
what is a transpiration stream
movement of water in a plant
water moves through the xylem vessels in a continuous transpiration stream from the roots to the leaves via the stem
this is to replace the water that has been lost through transpiration
describe the relationship between the rate of transpiration from the leaves and the speed of water molecules through the xylem?
as the rate of transpiration from the leaves increases…
…water molecules are pulled up the xylem quicker
what are some of the functions of transpiration?
transporting minerals
providing water to keep cells turgid to support the structure of the plant
providing water to leaf cells in photosynthesis
keeping the leaves cool
Note 
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