Download Chapter 12 – Plant structure

Junior Certificate Biology
more is sucked into the leaves through
the xylem vessels.
Plant structure
Part
Root
Stem
Leaf
The functions of transpiration are:
Function
1. Anchorage.
2. Absorb water and
minerals.
3. Store food.
1. To transport water through the
plant.
2. To carry minerals up from the
roots to the leaves.
3. To cool the plant.
1. Hold leaves up to the
light.
2. Hold up flowers
3. Transport water and
food.
The factors which affect the rate of
transpiration;
1. Sunlight – bright sunlight causes
the pores to open and a lot of
water to be lost.
2. Heat – warm temperatures cause
the pores to open and a lot of
water loss.
3. Wind – a gentle wind will cause
pores to open and loss of water.
4. Humidity – low humidity (dry air)
increases the amount of water loss
from the plant.
5. Soil water – high amounts of water
in the soil means high intake of
water by plants. This will result in a
lot of water lost by the plant.
1. To make food by
photosynthesis.
Flowers
1.To make fruit and
seeds for reproduction.
Buds
1. To make new flowers
and leaves.
Transport in Plants
The flow of water from the roots to the
leaves is called the transpiration
stream.
Transpiration is the loss of water
vapour from the surface of the leaf.
Water is lost from the leaf through tiny
pores on the undersurface called
stomata. As water is lost from the leaf
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Junior Certificate Biology
Experiment; To demonstrate
transpiration
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Set up a potted plant, as shown
above.
Leave the plant in sunlight for
several hours.
The bag will become ‘fogged-up’.
Test this liquid from the inside of
the bag with blue cobalt chloride
paper.
The paper will turn pink, indicating
that the liquid is water.
Set up a plant, as shown above.
Leave the plant in sunlight for
several hours.
After several hours, it will be
noted that the level of water in
the test-tube has fallen.
The only explanation for this is
that the roots must have
absorbed the water.
Note; The layer of oil is to
prevent the water level from
dropping due to evaporation.
Experiment; To the show the
movement of water in plants
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Experiment; To show the absorption of
water by the roots
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Use the same set-up as for the
previous experiment, except use
red dye food dye instead of water.
After several days, remove the
plant and rinse off the excess dye.
Cut across the root and examine
the cut section. You should note a
red spot in the middle of the root.
Cut across the stem and examine
the cut section. You should note
several red spots around the
outside of the stem.
This demonstrates that water
travels up the middle of the root
and along the outer cells of the
stem.