Key Stage 3 (KS3) Plants Practice Test

Plants respond to light primarily through a growth response known as phototropism. This is a specific behavior where plants grow towards light sources. The mechanism behind this involves the distribution of hormones within the plant, particularly auxins, which promote cell elongation on the side of the plant that is away from the light. Consequently, the plant bends towards the light as those cells grow faster. This adaptation allows plants to maximize their light exposure, which is essential for photosynthesis, the process they use to convert sunlight into energy.

The other options, while related to plant behavior and adaptation, do not specifically describe the primary response of plants to light. Developing deeper roots typically pertains to seeking water and nutrients rather than directly responding to light. Changing leaf color can occur due to various environmental factors such as temperature or health rather than a direct response to light. Increasing water intake is more about moisture absorption and is not a direct response mechanism to light stimuli. Phototropism distinctly illustrates how light specifically influences plant growth directionally, making it the most accurate description of their response to light.