Studies on nodule functioning and hydrogen peroxide scavenging enzymes under salt stress in chickpea nodules

Abstract

Forty-five day old chickpea plants grown in dune sand in earthenware pots under natural light conditions were subjected to 50 and 100 mM NaCl treatments for 7 and 14 days, respectively. NaCl treatment of the plants accelerated nodule greening, accompanied by a concomitant decrease in leghemoglobin (Lb) content of the nodules. With 50 mM NaCl, increase in duration of the treatment from 7 to 14 days, the Lb content recovered by 15% (rising from 41% to 56% of the control). However, under NaCl 100 mM treatment Lb content declined further dropping from 27% to 18% of the control 14 days after treatment (DAT). The decline in nodule cytosolic proteins was much slower as compared to that in Lb content thus indicating that preferential degradation of Lb occurs under salt treatments. A 63% and 70% decrease in acetylene reduction activity (ARA) was observed with 50 and 100 mM NaCl, respectively, seven DAT. However, 14 DAT 50 mM NaCl treated plants showed considerable recovery with the ARA increasing from 37% of the control to 71% of the control. But with 100 mM NaCl, the ARA declined further 14 DAT. Contrary to other parameters the total soluble carbohydrates increased under salt stress thus suggesting that they are playing an osmoregulatory role which is also evident from the considerable recovery in ARA under 50 mM NaCl treatments 14 DAT. Among the H 2 O 2 scavenging enzymes studied, peroxidase registered a 2.5 to 3 fold increase 7 DAT with 50 and 100 mM NaCl, respectively. Fifty and 100 mM NaCl treatment induced a 21% to 31% decline in catalase activity 7 DAT and 44% to 47% decline, 14 DAT. Glutathione reductase and ascorbate peroxidase activity also decreased under salt stress but to lesser extent as compared to catalase. These results thus indicate that there is a link between N 2 fixation and protection against H 2 O 2 .