The leaves of Mimosa pudica plants are made of a number of structures known as pinnae. The pinnae fold when the leaf is touched. This closes the leaf. Fig. 4.1 shows an open leaf of M. pudica before it is touched. Fig. 4.2 shows the same leaf that has closed after being touched. [Figure 4.1] [Figure 4.2]

1. (a)A touch stimulus to an M. pudica leaf causes an action potential to be generated. The action potential results in changes in cells, which cause the leaf to close. Fig. 4.3 shows the mechanism in M. pudica cells that causes the leaf to close. The leaves of M. pudica and the leaves of Venus fly traps move in response to touch stimuli, but the mechanisms that cause the responses are different. Describe the differences between the mechanism shown in Fig. 4.3 and the mechanism that causes the closure of the modified leaves in Venus fly traps.[3]
2. (b)The rate of photosynthesis decreases by 40% when the leaves of M. pudica close. Explain why the rate of photosynthesis decreases when the leaves of M. pudica close.[2]
3. (c)Plants can carry out cyclic photophosphorylation and non-cyclic photophosphorylation during the light-dependent stage of photosynthesis. These processes occur at the grana of chloroplasts. Outline the similarities and differences between cyclic photophosphorylation and non-cyclic photophosphorylation.[6]

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