The tomato plant, Solanum lycopersicum, does not tolerate periods of drought (water shortage). Researchers have produced a tomato plant that has an improved tolerance of drought. The researchers measured the width and the length of open stomata in plants that are tolerant of drought and tomato plants that are not tolerant. Fig. 3.1 is the formula used to calculate the size of an open stoma (stomatal aperture). stomatal aperture = width of open stoma length of open stoma Fig. 3.2 shows the mean stomatal aperture of the two groups of tomato plants. Fig. 3.3 shows the rates of transpiration of the two groups of tomato plants when kept in identical conditions of drought. The water uptake of leafy shoots taken from the two groups of tomato plants was measured using potometers. The leafy shoots were of similar mass and had the same number of leaves. The results are shown in Fig. 3.4.

1. (a)With reference to Fig. 3.2, Fig. 3.3 and Fig. 3.4, describe and explain the differences between the plants that are drought tolerant and the plants that are non-drought tolerant.[5]
2. (b)The nuclei of plants produce small lengths of RNA known as microRNAs. MicroRNAs in guard cells have been shown to prevent the synthesis of some proteins. The guard cells of the drought-tolerant tomato plants produced more microRNA molecules than the guard cells of the non-tolerant plants. MicroRNA molecules do not prevent transcription but interact with messenger RNA (mRNA). Suggest how this microRNA can interact with mRNA to prevent the production of proteins in guard cells of S. lycopersicum.[3]

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