Which type of plant hormones regulate growth and development in response to environmental stimuli?

The correct answer is phytohormones, as they encompass a broad category of plant hormones that regulate growth and development in response to environmental stimuli. Phytohormones, including auxins, gibberellins, and cytokinins, play crucial roles in processes such as cell elongation, fruit development, and the response of plants to light and gravity.

Auxins, for example, are primarily involved in the elongation of plant cells and help in processes like phototropism, where plants grow towards light. Gibberellins promote seed germination and stem elongation, while cytokinins are involved in cell division and shoot formation. While each of these hormones has specific roles, referring to them collectively as phytohormones highlights their shared function in responding to environmental cues and regulating various growth processes in plants.