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 differential tolerance to salinity ha ve been compared by analysing growth, photosynthesis, nodulation, nitrogena se activity, and carbon metabolism in the nodule cytosol, The aim was to he lp elucidate the relationships between, on the one hand, sucrose and malate metabolism in nodules and, on the other, the inhibition of nitrogen fixati on under salt stress, Chick-pea cultivars Pedrosillano (sensitive) and ILC1 919 (tolerant) inoculated with Mesorhizobium ciceri strain Ch-191 were grow n in a controlled environmental chamber and were treated with salt (0, 50, 75, and 100 mM NaCl) from sowing to harvest time (28 d), Plant growth and p hotosynthesis were more affected by salt in Pedrosillano than in ILC1919, A lso the effect of salt on nodulation and nitrogen fixation was much more pr onounced in Pedrosiliano, The increase in nodular mass in ILC1919 can parti ally counteract the inhibition of nitrogenase activity, The enzymes of sucr ose breakdown were inhibited by NaCl, but in ILC1919 a rise in alkaline inv ertase was observed with salinity, which could compensate for the lack of t he sucrose synthase hydrolytic activity. The activity of PEPC was stimulate d by salt in ILC1919, Also, this cultivar showed higher malate concentratio ns in root nodules.