ADAPTIVE RESPONSES TO SALINITY: SEED GERMINATION TRAITS OF SONNERATIA APETALA ALONG SALINITY GRADIENT IN SUNDARBANS, BANGLADESH

Water and soil salinity of the Sundarbans are increasing due to continuous reduction in fresh water flow from upstream and noticeable change in rainfall pattern. Sonneratia apetala is an important tree species for coastal afforestation in Bangladesh. It was hypothesised that S. apetala may show adaptive responses to salinity gradient in terms of morphological and physiological traits. This study examined the adaptive responses of S. apetala, growing in three saline zones (less, moderate and high) of the Sundarbans, in terms of fruit weight and seed germination traits. The fruits of less saline zone was comparatively heavier (9.09 +/- 0.08 g) than moderate and high saline zone. The final germination percentage (FGP), germination initiation time (GIT) and germination index (CI) of S. apetala seeds varied significantly (ANOVA, p < 0.05) among the saline zones and saline treatments. The FGP and GI showed a significant (p < 0.05) negative correlation with salinity levels. While, GIT showed a significant (p < 0.05) positive correlation with salinity treatments. Seeds of moderate and high saline zones germinated faster and vigorously than the seeds of low saline zone at higher salinity levels.