Effects Of Exogenous Γ-ambutyric Acid On Relevant Indicators Of Carbon And Nitrogen Metabolism Of Non-heading Cabbage Under Waterlogging Stress

In the present study,waterlogging-tolerant non-heading Chinese cabbage cultivar Xinxiaqing’ and waterlogging-sensitive cultivar ’Xinaiqing’ were chosen as experimental materials,and were cultivated in flooding conditions simulated in the greenhouse.The study has researched the changes of non-heading Chinese cabbage seedling growth and photosynthetic characteristics,nitrogen and carbon metabolism under waterlogging stress by spraying exogenous spraying γ-aminobutyric acid(GABA);and has investigated the mechanism of exogenous GABA alleviating waterlogging stress damage,and has provided the theoretical basis for finding effective measures of improving plant ability-resistant to waterlogging.The main research results were as follows:1.Waterlogging stress significantly inhibited the two varieties of non-heading Chinese cabbage seedling growth,plant the plant height,root length,leaf area and fresh weight were significantly decreased;but spraying suitable GABA on foliar can effectively alleviate the inhibition on the growth of stress,the growth index were sigificantly improved,and the effect of 40 mmol/L concentration treatment was the best.Constrated with CK,chlorophyll content of the seedlings under flooding stress significantly decreased,but the suitable concentrations of GABA could increase chlorophyll a,chlorophyll b and total chlorophyll,and when the 40mmol L GABA,they reached maximum,significantly higher than the flooding treatment group;and effectively alleviated destruction on photosynthetic pigment from waterlogging stress.It had illustrated that the flooding treatment significantly reduced the photosynthesis efficiency,Fv/FM,QP3 ETR and yield decreased significantly,QN increased significantly,the fluorescence system of seedlings were destructed.And the PN,GS and TR decreased significantly,Cl increased significantly,the photosynthetic efficiency decreased significantly;but spraying suitable GABA on foliar could effectively alleviate inhibition of photosynthesis under waterlogging stress.The effect on Xinxiaqing was better than ’Xinxiaqing’.2.With the extension of stress time,waterlogging stress significantly decreased the content of soluble protein,increased the content of free amino acid,ammonium nitrogen(NH4+-N)and nitrate nitrogen(NO3--N)significantly.And the activity of nitrate reductase(NR),glutamine synthesis enzyme(GS),glutamate synthase(GOGAT)and glutamine dehydrogenase(GDH)were also increased significantly.But exogenous 40mmol/L GABA can effectively increase the content of soluble protein under waterlogging stress;further increased the content of free amino acid;decreased the content N3--N and NH4+-N;improved the activity of NR,GS,GOGAT;but the activity of GDH decreased little.The effective period of GABA was in three to five days.The effect on Xinxiaqing was better than ’Xinxiaqing’.It showed that spraying GABA under waterlogging stress could effectively alleviate the resistance on the growth,had some regulatory role in nitrogen metabolism,and the regulation on nitrogen metabolism of ’Xinxiaqing’ under waterlogging stress was better the ’Xinaiqing’.3.Compared to normal cultivation,flooding stress on non-heading Chinese cabbage seedling increased the content of leaf starch,soluble sugar and sucrose,and improved the activity of SS,SPS,AI,and ALDOLASE.And exogenous 40mmol/L GABA increased the content of leaf starch,soluble sugar and sucrose further;improved the activity of SS,SPS,AI,ALDOLASE.The effective period of GABA was in three to five days.And the effect on Xinxiaqing was better than ’Xinxiaqing’.These results suggested that GABA was involved in the regulation of the metabolism of carbohydrates on non-heading Chinese cabbage,and played an important role in adaptability to waterlogging stress plays;and the regulation on carbon metabolism of ’Xinxiaqing’ under waterlogging stress was better the’Xinaiqing’.