Far red light control of elongation in light-grown bean hypocotyl: Effect on different age zones and interaction with indole-3-acetic acid

摘要

The effect of far red light on the light-grown bean hypocotyl and its interaction with indole-3-acetic acid (IAA) were studied. Elongation of younger zones of the hypocotyl was inhibited but that of older zones was promoted by far red light. This was controlled by phytochrome. Both the hook and shank portions could receive far red light and its effect could be transmitted to either portions of the hypocotyl.When IAA was applied to the upper cut surface of the hypocotyl unit, elongation of the shank portion was promoted even without far red irradiation. IAA did not change the aspect of the growth curves but amplified the elongation of each zone. When IAA was applied to each zone of the shank portion, elongation of zones older than the treated one was promoted but that of younger zones was inhibited. This effect was emphasized by far red light. When IAA was applied to the older shank portion, elongation of the treated zone was synergistically promoted by IAA and far red light, but when applied to the elbow or younger shank portion, far red light completely nullified the promoting effect of IAA.