Adaptive phenotypic plasticity of Avicennia officinalis L. across the salinity gradient in the Sundarbans of Bangladesh

Abstract

Adaptive phenotypic plasticity of Avicennia officinalis across the salinity gradient in the Sundarbans of Bangladesh was studied. Propagule morphology was compared through use of a completely randomized design. Propagule growth initiation traits across the salinity gradient (from 0 to 35 ppt at 5 ppt interval) were studied by means of a randomized block design. Propagules showed variability in length, width, and weight across the salinity gradient in the Sundarbans. Propagule growth initiation time, mean growth initiation time, growth initiation index, and propagule growth initiation percentage of A. officinalis varied significantly with the increasing salinity and among low, medium, and high saline zones. However, propagules originating from the high and medium saline zones started their growth initiation more rapidly and vigorously at high salinities compared to those from the low saline zone. Therefore, A. officinalis exhibited adaptive phenotypic plasticity in terms of variability in propagule size and weight as well as physiologically adaptive plastic responses during propagule growth initiation across the salinity gradient in the Sundarbans. A. officinalis in high and medium saline zones of Sundarbans is the most salt-adapted phenotype, and a good knowledge about this will be widely useful for successful regeneration, coastal afforestation, and conservation of this species in increasing saline environments in the future.