Which substance can control physiological processes in plants and may be synthetic?

The correct answer is indicated as a hormone because hormones play a vital role in regulating various physiological processes within plants. These substances, often found naturally within plants, can also be synthetically produced to initiate or modify growth responses, such as cell division, elongation, and differentiation, among others.

In the context of plant physiology, hormones can influence processes like flowering, fruiting, and even the response to environmental stimuli. For example, auxins promote stem elongation, while gibberellins can trigger seed germination and flower development. The use of synthetic hormones in agriculture allows for enhanced control over these processes, making them a powerful tool in modern plant management.

While pesticides, fertilizers, and insecticides also play significant roles in plant health, their functions differ dramatically from those of hormones. Pesticides are primarily designed to eliminate pests, fertilizers provide essential nutrients for growth, and insecticides target insect pests specifically. None of these options manipulate the inherent physiological processes of plants in the way hormones do.