Effects Of Ca?NO₃?₂ Stress On Mitochondria And Nitrogen Metabolism In Cucumber Seedlings Root

Cucumber is one of the important vegetable crops for facility.In recent years,with the continuous development of vegetable facilities,research on plants salt tolerance has been deepened.Thorough studies of plant mitochondria have suggested salt tolerance mechanisms and the development of salt-tolerant varieties.Salt-sensitive'CQ'and salt-tolerant'BM'were used as test material and treated with Ca?NO₃?₂ stress.Root morphology,mitochondrial oxidative damage,antioxidation systems,mitochondrial electron transport chain,mitochondrial membrane properties and nitrogen metabolism were determined in this experiment.The main results are as follows:1.Six cucumber varieties were tested for their roots after Ca?NO₃?₂ treatment,then salt-sensitive'CQ'and salt-tolerant'BM'were selected as test materials.The Ca?NO₃?₂stress concentration was 70 mM Ca?NO₃?₂.2.Ca?NO₃?₂ stress inhibited root growth of cucumber seedlings that reduced root length,decreased surface area and number of root tips,and significantly increased root diameter.'BM'root length,surface area and number of root tips were significantly larger than'CQ'.Root diameter'BM'was lower than'CQ'.3.Mitochondrial MDA content,H₂O₂ content and O₂.^-producing rate of two cucumber roots were gradually increased with Ca?NO₃?₂ treatment.The activity of SOD and POD were gradually increased,and CAT activity was gradually decreased.These results showed that salt stress could increase oxidative damage of cucumber,but the antioxidant enzyme was damaged,which led to oxidative damage increase.4.Electron transport chain activity of'BM'was higher than'CQ'under Ca?NO₃?₂ stress.‘BM'activity in the complex II had higher than'CQ'.With increasing of complex II activity,it increased electron transfer and energy supply.5.Ca?NO₃?₂ stress was destroyed membrane structure of mitochondria,so that mitochondrial body tended to bend,double membrane digestion,internal hollow.With destruction of structure and mitochondrial permeability increased,and fluidity decreased,the ion through increased.Then mitochondrial energy supply was stopped for a certain period of time.6.Under the stress of Ca?NO₃?₂,NO₃^-content of seedlings increased significantly.The contents of NH₄⁺and NO,activities of NR,NIR and NOS were decreased significantly.