A student investigated the effect of wind speed on the rate of transpiration in a plant shoot. Figure 1.1 shows the apparatus used. As water is taken up by the plant shoot, the air bubble in the capillary tube moves towards the shoot.

Figure 1.1, a potometer, marked not to scale: a plant shoot sealed into a water-filled tube joined to a reservoir with a tap, and a horizontal capillary tube lying along a ruler with an air bubble in it, its end dipping into a beaker of water

The student used a fan set at different speeds to change the wind speed. He measured the distance travelled by the air bubble in 300 seconds. The results of the student’s investigation are shown in Table 1.1.

1(a)(i)Maths Skills BiologyEasy1 mark

Calculate the rate of transpiration for a wind speed of 10 m s

^{- 1}

where the distance moved by the bubble was 135 mm in 300 seconds. Write your answer in Table 1.1.

wind speed / m s $^{- 1}$	distance travelled by the air bubble in 300 s / mm	rate of transpiration / mm s $^{- 1}$
0	2	0.01
2	12	0.04
4	20	0.07
6	35	0.12
8	115	0.38
10	135	Table answer r6_rate of transpiration / mm s$^{-1}$

1(a)(ii)Plant Structure TransportMedium2 marks

Describe the effect on the rate of transpiration of increasing the wind speed in this investigation.

Answer

0 words

1(a)(iii)Plant Structure TransportEasy1 mark

Suggest why the rate of transpiration is only an estimate of water uptake in a plant.

Answer

0 words

1(a)(iv)Plant Structure TransportEasy2 marks

State two other environmental factors that can change the rate of transpiration in a plant shoot.

Two answers required.

1(b)Plant Structure TransportHard4 marks

Explain how transpiration causes the movement of water in the xylem.

Answer

0 words