Recalcitrant Behaviour of the Seeds of Endangered Syzygium Zeylanicum (L.) DC

Syzygium zeylanicum (L.) DC. is an endangered tree species indigenous to Western Ghats region and it is traditionally utilized to cure many diseases. The species is sparsely distributed in their natural stands with poor natural regeneration. The present investigation was undertaken with a view to understand the reasons that hinder regeneration process. Physiological, embryological and hormonal changes during embryogeny were studied to understand any developmental anomalies. Embryogeny was typical as that in other dicots with globular, heart, torpedo and cotyledonary stages and no deformations could be identified. Physiological data showed two distinct phases during embryogeny; histodifferentiation and reserve food accumulation stages, and no maturation drying stage. The predominant PGRs identified during histodifferentiation process were IAA (9.96 ng gfw −1 ), GA 4 (9.33 ng gfw −1 ), BA (484.85 ng gfw −1 ), ABA (10.58 ng gfw −1 ), 24-epiBL (18.34 ng gfw −1 ) and cisJ (10.92 ng gfw −1 ). Reserve food accumulation phase was marked by the rapid influx and accumulation of IAA (140.17 ng gfw −1 ), IBA (21.43 ng gfw −1 ), GA 4 (25.53 ng gfw −1 ), BA (790.04 ng gfw −1 ), ABA (111.31 ng gfw −1 ) and cisJ (15.21 ng gfw −1 ) from the maternal tissues. The seed shedding stage showed the accumulation of higher quantities of GA 4 (90.12 ng gfw −1 ) and lower ABA (26.93 ng gfw −1 ) with GA 4 /ABA ratio of 3.34 indicating clear hormonal antagonism during germination. SA was found to accumulate in exceptionally high quantities during embryogeny (from 5335.88 ng gfw −1 to 14699 ng gfw −1 ). Germination and desiccation study indicated the extreme desiccation intolerance of the seeds and the critical moisture content was found to be 23.70% with an electrolyte leakage of 134.65 µS cm − 1 . The results indicate the true recalcitrant behaviour of Syzygium zeylanicum seeds.