Signals of salinity fluctuation in Nypa fruticans seedling growth: a case study from lower Gangetic plain

Abstract

Salinity induced pigment changes were studied in hydroponically grown plants of a freshwater loving mangrove, Nypa fruticans. The seedlings of the species were analyzed for Chl a, Chl b, total chlorophyll, Chl a:b ratio and carotenoid at five different salinity levels. The concentrations of chlorophyll and carotenoid pigments exhibited significant negative correlations with salinity (p < 0.01). The total chlorophyll expressed, on unit fresh wt. basis decreased by 25.00%, 32.72%, 33.01% and 29.34% at the end of 7th, 14th, 21st and 30th day due to salinity change from 2 to 15 psu. The carotenoid decreased by 28.57%, 47.37%, 31.25% and 66.66% at the end of 7th, 14th, 21st and 30th day due to similar change in salinity level. The Chl a:b ratio in the plant remained almost constant throughout the period of investigation. The results show that Nypa fruticans of Indian Sundarbans region can be sustained and propagated under low saline environment. At 15 psu, the plants become acclimated in one to two weeks, but at 20 psu the seedlings could not survive. The present study is extremely relevant as the Central Indian Sundarbans of Lower Gangetic Plain is experiencing a gradual rise in salinity over a period of two decades.