Comparative study of nitrogen fixation and carbon metabolism in two chick-pea (Cicer arietinum L.) cultivars under salt stress

Two cultivars of Cicer arietinum with differentialtolerance to salinity have been compared by analysing growth,photosynthesis, nodulation, nitrogenase activity, and carbon metabolism inthe nodule cytosol. The aim was to help elucidate the relationshipsbetween, on the one hand, sucrose and malate metabolism in nodules and, onthe other, the inhibition of nitrogen fixation under salt stress. Chick-peacultivars Pedrosillano (sensitive) and ILC1919 (tolerant) inoculated withMesorhizobium ciceri strain Ch-191 were grown in acontrolled environmental chamber and were treated with salt (0, 50, 75, and100 mM NaCl) from sowing to harvest time (28 d). Plant growth andphotosynthesis were more affected by salt in Pedrosillano than in ILC1919.Also the effect of salt on nodulation and nitrogen fixation was much morepronounced in Pedrosillano. The increase in nodular mass in ILC1919 canpartially counteract the inhibition of nitrogenase activity. The enzymes ofsucrose breakdown were inhibited by NaCl, but in ILC1919 a rise in alkalineinvertase was observed with salinity, which could compensate for the lackof the sucrose synthase hydrolytic activity. The activity of PEPC wasstimulated by salt in ILC1919. Also, this cultivar showed higher malateconcentrations in root nodules.