Parental influences on salt adaptive divergence of Sonneratia apetala (Buch.-Ham.) seedlings along the salinity gradient in the Sundarbans of Bangladesh

Abstract

Salt adaptive variability facilitates mangroves to cope with salinity increase due to climate change. Sonneratia apetala is a pioneer mangrove species growing in the less-saline, moderate-saline and high-saline zones of the Sundarbans. A growth study with S. apetala seedlings of the three saline zones was conducted at different salinities in randomized block design to examine the parental effects on the variability in salt adaptability of this species along the salinity gradient in the Sundarbans. The highest survival (100%) from 0 to 10% salinities indicates the facultative nature of S. apetala. The survival, chlorophyll, diameter, height and biomass increment, proline, nutrients (N, P and K) and Na accumulation in different parts of the seedlings collected from the less-saline, moderate-saline and high-saline zones didn't vary significantly (p > 0.05) up to 20% salinity. However, at higher salinities, all the growth traits of the seedlings of the moderate-saline and high-saline zones were significantly (p<0.05) higher than those of the less-saline zone. These results demonstrated that the seedlings of S. apetala of the moderate-saline and high-saline zones are more salt adaptive than those of less-saline zone and clearly reflect the parental effects of S. apetala on its seedlings growth under different salinities. This divergence in salt adaptability among different saline zones due to parental effects makes S. apetala survive and grow in a wider salinity range in the Sundarbans and coastal plantations in Bangladesh.