MORPHOLOGICAL SIDE-EFFECTS OF USING GIBBERELLIC-ACID TO INDUCE GERMINATION - CONSEQUENCES FOR THE STUDY OF SEED DORMANCY

To assess the evolutionary significance of persistent seed banks, phen otypes of naturally germinating seeds must be compared with those that remain dormant under the same environmental conditions. Dormant seeds can often be induced to germinate by application of gibberellic acid (GA). However, this method is valid only if there are no phenotypic '' side effects'' of GA that could confound comparisons between dormant a nd naturally germinating seeds. We examined this assumption in Lesquer ella fendleri, a short-lived perennial mustard of the desert Southwest . We exposed 3840 seeds from 16 maternal sibships to two different GA treatments (0 or 1 g/L GA) in two different germination environments ( greenhouse and growth chamber), and measured germination and postgermi nation traits. As expected, application of GA increased germination. G A also had strong and long-lasting effects on seedling morphology. See ds that received GA developed into seedlings that were taller, with fe wer but longer leaves, than seeds that did not receive GA. Effects of GA on both dormancy and postgermination traits varied among maternal s ibships. Our results indicate that for this species and this concentra tion of GA, morphological effects can be substantial. Further study is required to determine whether such side effects are found for lower c oncentrations of GA, or under conditions that encourage faster seedlin g growth. Nonetheless, the present results illustrate the importance o f testing potential confounding effects of GA in studies of the evolut ion of seed dormancy and its influence on postgermination traits.