Effect of Sodium Chloride on Photosynthesis of Lemna minor L.

Abstract

Summary Lemna plants grown in the presence of salt showed, in comparison to control, increased activities of PEP-carboxylase, NAD+-specific MDH, NADP+-specific malic enzyme, RuDP-carboxylase and ribulose-5-phosphate kinase, although the activities of NADP+-specific MDH, NADP+-specific GPD, and NAD+-specific GDP remained more or less unaffected. The lowest salt concentration (17 mM) promoted the rate of 14C incorporation, but higher concentrations proved inhibitory. An inhibition in the rate of photosynthesis of Lemna plants grown in the presence of higher salt concentrations may be due to the inhibition of Hill-reaction activity. Salt had no effect on the pattern of 14CO2 fixation into photosynthetic products, nor did it affect the formation of malate to any significant extent. An appreciable influx of sodium and chloride ions could be detected in the salt grown Lemna plants. In comparison to control, ABA level was found to be about 1.5 times higher in the salt treated plants. The implications of the results in relation to adaptation of plants under stress have been discussed.