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biology 0610printed 97 · PDF 97
328 pagesrevision 46933
printed 97 · PDF 97
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Core
1
2
Describe transpiration as the loss of water vapour
from leaves
State that water evaporates from the surfaces of
the mesophyll cells into the air spaces and then
diffuses out of the leaves through the stomata as
water vapour
Investigate and describe the effects of variation
of temperature and wind speed on transpiration
rate
Supplement
Explain how water vapour loss is related to:
the large internal surface area provided by the
cells and the size and number of stomata
Explain the mechanism by which water moves
upwards in the xylem in terms of a transpiration
pull that draws up a column of water molecules,
held together by forces of attraction between
water molecules
Explain the effects on the rate of transpiration of
speed and humidity
7 Explain how and why wilting occurs
Core Supplement
1 Describe translocation as the movement of
sucrose and amino acids in phloem from sources
to sinks
2 Describe:
(a) sources as the parts of plants that release
sucrose or amino acids
(b) sinks as the parts of plants that use or store
sucrose or amino acids
3 Explain why some parts of a plant may act as a
source and a sink at different times
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