Everything Life Sciences Grade 10

• Transpiration: Transpiration is the loss of water from the stomata of plants. It creates
  a ’suction’ or transpirational pull that is important for the movement of water through
  the plant. Transpiration is affected by environmental conditions e.g wind, temperature,
  humidity and light intensity. The rate of transpiration is measured using a potometer.
  In order to prevent excessive transpiration, plants have developed adaptations such
  as thickened cuticle, position of stomata, hairs on leaves, reduction of leaf size, leaf
  spines, leaf arrangements and rolling of leaves.


• Translocation: Translocation is the transport of food material (synthesised in the leaves)
  to other parts of the plant via phloem. This mode of transport is multi-directional,
  but requires energy as it occurs by active transport against a concentration gradient.
  Phloem vessels consist of sieve-tube elements and companion cells which are con-
  nected by plasmodesmata. Companion cells act as the regulators and energy stores of
  the phloem.


• Wilting and guttationare processes of water loss in the plant. Wilting entails excessive
  loss of water through plasmolysis resulting in excessive cell death, at times resulting in
  death of the entire plant. Guttation is the release of water via the hydathodes due to
  high humidity.


• Manufactured foodis moved in the phloem tube. Phloem vessels have attached com-
  panion cells which act as energy stores to allow movement in the vessel.

Exercise 6 – 1: End of chapter exercises

1. The water loss in two plants was recorded over a 12 hour period. Study the information
   below and then answer the questions that follow. The results for the two plants were
   recorded in the following table.

Time of

Day

06h00 08h00 10h00 12h00 14h00 16h00 18h00

Water

loss in

Plant A

(cm^3 )

0,0 0,4 1,6 6,0 9,0 8,0 7,6

Water

loss in

Plant B

(cm^3 )

0,2 0,7 4,0 14,0 19,0 18,2 17,7

a) What is the correct biological term for water loss in a plant?

b) From which plant was the greatest amount of water loss recorded?

c) Which time of day was the greatest water loss recorded for both Plants A and B.

Why do you think this is so?

d) At 18h00 the rate of water loss lower. Why did this occur?

e) What is the apparatus that was used in the laboratory to measure the rate of water

loss in plants A and B.

2. What do you understand by guttation and how does the process of guttation occur?


3. Tabulate the differences between guttation and transpiration.


4. Briefly discuss the movement of water through the dicotyledonous root.


5. Give a short explanation for the following:
   
   
   • Capilliarity
   
   
   
   

186 6.5. Summary