Effects of calcium nitrate stress on nitrogen and carbon metabolism in hydroponically-grown grafted eggplant seedlings

To investigate the salt tolerance mechanism of grafted eggplant,and response of its nitrogen and carbon metabolism system under stress by excess of Ca(NO3)2,using a Japanese salt tolerant eggplant cultivar Torvum Vigor(Solanum torvum Swartz) as rootstock and cultivar Suqiqie(Solanum melongena L.) as scion,grafting was made to compare the changes of nitrogen metabolism and carbon metabolism in leaves of hydroponically-grown grafted and non-grafted eggplant seedlings under 80 mmol/L Ca(NO3)2 stress.Under stress by excess of Ca(NO3)2,the plant height and biomass accumulation of grafted eggplant seedlings were significantly higher than those of non-grafted seedlings.The contents of NO3-and NH4+ in the leaves of both grafted and non-grafted eggplant seedlings increased significantly at the early stage of treatment,then decreased significantly,however,the contents of NO3-and NH4+ in grafted seedlings were significantly higher than those of non-grafted seedlings with prolonged stress time.Nitrate reductase(NR) activity in the leaves of grafted eggplant seedlings was significantly higher than that of non-grafted seedlings since the 9th day of treatment.Soluble protein content in the leaves of grafted eggplant seedlings was significantly higher than that of non-grafted seedlings during the whole stress process.Glutamine synthetase(GS) activity in the leaves of eggplant seedlings increased significantly at the early stage of treatment,then decreased significantly,however,GS activity in grafted eggplant seedlings were significantly higher than that of non-grafted seedlings with prolonged stress time.Soluble sugar content in the leaves of grafted eggplant seedlings increased significantly at the early stage of treatment,then decreased significantly,but soluble sugar content in non-grafted eggplant seedlings decreased and was significantly lower than that of grafted seedlings in the whole stress time.Starch content in leaves of grafted eggplant seedlings was significantly higher than that of non-grafted seedlings,but activities of α-amylase and β-amylase in the leaves of grafted eggplant seedlings were both significantly lower than those of non-grafted seedlings.Under stress by excess of Ca(NO3)2,nitrogen metabolism and carbon metabolism in grafted eggplant seedlings were more efficient than those of non-grafted seedlings.Grafted seedlings were more tolerant to stress by excess of Ca(NO3)2,according to the efficiency of energy storage and physiological metabolism.