Influence of gibberellic acid on the sporulation of Azolla caroliniana, Azolla microphylla and Azolla pinnata

Azolla microphylla strains used in the study sporulate throughout the year while Azolla caroliniana and Azolla pinnata strains show sporulation only d uring November-March, the favourable period for sporulation. Application of gibberellic acid (GA) at a concentration of 2.5-100.0 mu g ml(-1) substant ially enhanced the sporulation frequency and number of sporocarps (mega plu s micro) per plant in Azolla microphylla (two strains) during the unfavoura ble period (September-October) by 77.3-200.0%. The increase in the number o f microsporocarps was more than that of the megasporocarps. The sporulation frequency and number of sporocarps in Azolla pinnata (two strains) and Azo lla caroliniana during the favourable season also increased considerably du e to GA (2.5-10.0 mu g ml(-1)) application. The optimum GA concentration fo r the sporulation of the three Azolla species was 2.5 mu g ml(-1), which wa s used in the subsequent investigations. Efficacy of GA for enhancing sporu lation was tested across 20 Azolla pinnata strains. A significant positive response was observed in all the strains. Of them, 17 strains for the sporu lation frequency and 15 strains for the sporocarp number showed a >25% incr ease due to GA treatment. Under field conditions, Azolla microphylla (two s trains), Azolla caroliniana and Azolla pinnata exhibited 66.0-88.1% higher sporulation frequency and 42.8-52.6% higher sporocarp number due to GA appl ication. However, the proportion of megasporocarps to total sporocarps did not change.