Effect of Salinity on Leaf Ionic Content and Photosynthesis of Taxodium distichum L.

Publisher Website
Google Scholar
Abstract
Bald cypress (Taxodium distichum L.) seedlings were subjected to flooding with salinity levels ranging from 0-140 moles m-3 NaCl. Imposition of salinity was designed to simulate the increase in salinity level which some of Louisiana''s [USA] extensive cypress forests are currently experiencing due to rapid subsidence in the Mississippi River Deltaic Plain. The effect of salt water on leaf tissue ion concentrations and subsequent changes in net photosynthesis were measured. Leaf concentrations of Na, K, Ca and Mg increased substantially as salinity of flood water increased. Net photosynthesis declined from 7.6 .mu.mol .cntdot. m-2s-1 to 0.9 .mu.mol .cntdot. m-2s-1 when salinity increased from 0-140 moles m-3 NaCl. Despite the parallel reduction in both stomatal conductance and net photosynthesis, the leaf internal CO2 concentrations remained relatively constant over the entire range of salt concentrations. These results suggest that elevated floodwater salinity causes excess accumulation of several ions in the bald cypress leaf tissue. Consequently, increase in leaf ionic content is primarily the cause of reductions in photosynthesis which is accompanied by simultaneous diffusional limitations caused by stomatal closure.