The Non-reversible Effects of Red and Far Red Light on the Content of Gibberellin-like Substance in Pea Internodes

The endogenous gibberellin-like substances, extracted from the third interriodes of 7-d-old etiolated pea seedlings were determined after short intervals following a brief light treatment. Red light of 660 nm induces a transient increase in gibberellins after 20 min, followed by a decline to a very low level within next 2 h. Far red light, applied immediately after red, did not reverse either effect, although the same light treatment did reverse the inhibition of internode elongation and the opening of the apical buds in the same plant. The possible relationship of gibberellin changes, phytochrome and these growth phenomena is discussed.