Experiments were carried out on plants living in different environments to measure the size of the leaf stomata at different times of the day - HSC - SSCE Biology - Question 11 - 2009 - Paper 1

In a dry environment, plants tend to close their stomata during the hottest part of the day to minimize water loss through transpiration. This behavior results in a graph that shows a reduced stomatal size during daylight hours, particularly at noon when temperatures are highest. Therefore, the best representation of a plant in a dry environment amongst the given graphs is option D. This graph demonstrates a pattern of stomatal size that remains relatively small during the day, peaking minimally at night, aligning with the adaptations of plants to conserve water.