The effect of photoperiod on the levels of seven endogenous gibberellins in the long-day plant Agrostemma githago L.

The following seven gibberellins (GAs) have been identified by gas chromatography-mass spectrometry in shoots and leaves of the long-day plant Agrostemma githago: GA53, GA44, GA19, GA17, GA20, GA1, and 3-epi-GA1. The levels of these compounds were measured, using selected ion monitoring, during photoperiodic induction. The levels of GA44, GA19, GA17, and GA20 all increased to a peak at eight long days (LD), followed by a decline, while the levels of GA1 and 3-epi-GA1 did not reach a peak until 12 LD. The level of GA53 remained steady over the first 10-12 LD. Later in the LD treatment the levels of GA53, GA44, GA19, and GA17 increased again. The rate of metabolism of all GAs except GA53 was higher after 12-16 LD than under short days. These data thus provide indirect evidence for an effect of photoperiodic induction on GA turnover in A. githago.