BIOL 1001 Chapter : OUTLINE Chap45
Document Summary
Plants perceive and respond to environmental stimuli by regulating growth and development through the action of chemicals called plant hormones or growth regulators. Phototropism (the bending of plants towards sunlight) was the first plant response discovered and studied by charles and francis darwin. Peter boysen-jensen discovered the mechanism of the bending. He found that a chemical is produced in the tip and moves down the shoot causing cell elongation. If the tip of the plant was cut off, then the elongation and bending is stopped. If the tip of the coleoptile was replaced, then the elongation and bending is restored. If the replaced tip of the coleoptiles had a porous gelatin slab between the severed tip and shoot, then the elongation and bending is restored. If the replaced the tip of the coleoptiles had a thin layer of non-porous mica between the severed tip and shoot, then the response to light remained blocked.
