Photosynthesis and water-use efficiency of some mangroves from Sundarbans, India

Abstract

We studied seasonal fluctuations in the rates of photosynthesis, transpiration, PAR, and stomatal conductance for 16 species of true mangroves from the Sundarbans region of West Bengal. Soil salinity and pH were also measured. Leaf temperatures were almost always higher than the ambient temperature. We observed considerable seasonal (summer vs winter) as well as interspecific variations in photosynthesis, with the highest rates occurring inHeritiera fomes (13.21 pmol m-2s-1) andAvicennia marina (11.8 mol m-2s-1), and the lowest inNypa fruticans (1.56 mol m-2s-1) andCeriops decandra (2.32 pmol m-2s-1), in many species, an abrupt rise in leaf temperature retarded the photosyn-thetic process. In winter, the rate of transpiration and stomatal conductance reached their maxima inA. marina (4.83 mmol ra-2s-1 and 124.23 m mol m-2s-1, respectively) and their mimima inExcoecaria agallocha (1.85 mmol m-2s-1 and 49.19 mmol m-2s-1, respectively). In contrast, the maximum summer readings were recorded in E.agallocha (6.07 mmol m-2s-1 and 192.74 mmol m-2s-1 respectively).