Plants communicate and regulate growth through electrical signals and chemical messengers like plant hormones. The document discusses several key plant hormones: 1) Auxins promote upward growth and inhibit lateral branching through a process called apical dominance. Gibberellins stimulate stem elongation and seed germination. 2) Abscisic acid induces stomatal closure in response to drought stress and may play a role in leaf senescence. 3) While many plant hormones are involved in growth and stress responses, their levels and effects are controlled through complex interactions rather than isolated pathways.