Growth Responses of Alaska Pea Seedlings to Visible Radiation and Gibberellic Acid.

SUMMIARY Exposure of a dwarf pea (Morse's Progress # 9) to a single brief irradiation with red light results in an inhibition of growth whiich persists for several days. After 4 or 5 days the plants resume growth at the dark-grown rate. Far-redl irradiation will negate the red effect. The effect of a series of gibberellin (loses on the growth responses of irra(liated or dark-grown peas has been determined. In the absence of applied gibberellin the growth of irradiated plants is inhibited compared to that in darkness. At saturating (loses of gibberellin the irradiated andl dlark-grown plants are the same height. The proportionate responses of irradiated andl dark-grown plants are equal at e(jual doses of gibberellin. It is concluded that visible radiation probably inhibits stem growth in this species througlh an effect on the level of endogenous gibberellin.