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.