Question

(a) A student investigates the effect of temperature on the rate of transpiration.
Transpiration is estimated by recording the loss in mass.
The student keeps one plant at 20°C and one plant at 40°C.
The student records the mass of each plant every day for 5 days.
Fig. 4.1 shows the apparatus the student uses.

Fig. 4.2 is a graph of the results.

    (i) Complete the sentences to describe and explain the results shown in Fig. 4.2.
       The mass of the plant kept at 40°C decreased in mass by …………………g between day 1 and day 5.
       As temperature increases, the water molecules gain more ……………………. energy.
       This increases the rate of evaporation from the surfaces of the …………….. cells.
       There is also an increase in the rate of diffusion of ………………. through the ………………… into the atmosphere.

   (ii) State how an increase in humidity would affect the results shown in Fig. 4.2.

(b) Water is transported to the leaves by xylem.
    (i) State how the water molecules are held together in the xylem.

    (ii) State one other function of xylem, apart from transport.

    (iii) State the name of one other transport tissue in plants.