Effects of Daylength on Endogenous Gibberellins in Leaves of Solanum andigena

Less gibberellin‐like activity was detected in extracts of potato leaves under short day than under long day conditions. Significant decreases in gibberellin levels were detected after two short day cycles. Using thin‐layer chromatography coupled with several solvent systems and various bioassays, at least four zones of gibberellin‐like activity, A, B, C and D were found in the potato leaf. Under long days only zones C and D were apparently present. However, preliminary purification using polyamide columns revealed that substances A and B were actually present in higher levels under long day than under short day conditions. The chloroplasts of leaves exposed to short days contained less gibberellin‐like substances than those from leaves grown under permanent long day conditions.