Effects Of Waterlogging Stress On Photosynthetic Characteristics And Roots Growth Of Non-heading Chinese Cabbage

Under different waterlogging stress,this paper studied the effects of waterlogging stress on photosynthetic characteristics,root respiration and ascorbic acid metabolism of two non-heading chinese cabbage cultivars by using simulation experiment.Under waterlogging stress,waterlogging stress can significantly affect the Photosynthetic parameters of non-heading chinese cabbage and with the increase of waterlogging time and flooding depth,the damage was more serious.Under waterlogging stress,the aerobic respiration in roots of non-heading chinese cabbage was inhibited,while the anaerobic respiration was promoted.Waterlogging treatment can lead to the accumulation of reactive oxygen species and the rising of key enzymes activities and antioxidant content in ascorbic-glutathione cycle,and then the reducing in the end of waterlogging stress.The main research results showed that:1.Under the waterlogged conditions,the net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)of non-heading chinese cabbage seedlings decreased significantly,while the intercellular carbon dioxide concentration(Ci)was significantly increased,indicating that non-stomatal limitation may be the main reason of the decrease of Pn.After different level of waterlogging stress,the transpiration rate(Tr)and water use efficiency(WUE)were decreased significantly,indicating that the different waterlogged treatment had different degree of damage to the function of water use of the leaves.2.With the prolongation of waterlogging time and the increase of waterlogging depth,the chlorophyll content of non-heading chinese cabbage seedlings were decreased significantly,but the Chla/Chlb value of Chla/Chlb maintained at a higher level,which means the decent degree of chlorophyll a content less than chlorophyll b content.In the photosynthetic process,more chlorophylls a were combined with reaction center of photosystem,while chlorophyll b mainly combined with the light harvesting protein complex.Regulating the value of Chla/Chlb can reduce the damage of waterlogging stress on the center of the photosynthesis.3.Under the waterlogging treatment,the maximal photochemical efficiency(Fv/Fm),electron transport rate(ETR),photochemical quenching coefficient(qP)and PS ? effective photochemical quantum yield(Yield)were significantly decreased,while the non photochemical quenching coefficient(qN)increased significantly,which showed that waterlogging stress decreased the primary conversion of light energy of photosystem ?,inhibiting the electron transportation and photosynthetic primary reaction process of photosynthesis and the energy accumulation.4.Compared with the control,the root fresh weight,root length,root activity of non-heading chinese cabbage were suppressed significantly after different waterlogging stress,and the decent degree of semi-submerged treatment was more than root submerged.The lactate dehydrogenase(LDH)and alcohol dehydrogenase(ADH)activity were significantly increased,while the malate dehydrogenase(MDH)and succinate dehydrogenase(SDH)activity decreased significantly,and the semi-submerged treatment fell more than root submerged.5.Waterlogging stress significantly increased the Hydrogen Peroxid content(H2O2)and the producing rate of superoxide anion radical(O2-)in non-heading chinese cabbage seedlings.With the rising stress levels increase,the Hydrogen Peroxid content(H2O2)and the producing rate of superoxide anion radical(O2-)increased.Under the waterlogging treatment,the the abscisic acid(ASA)content,glutathione(GSH)content,ascorbic acid peroxidase(APX),dehydroascorbic acid reductase(DHAR),reductase(GR)activity,dehydroascorbic acid(DHA)content and oxidized glutathione(GSSG)content were significantly increased,while the the ASA/DHA value and GSH/GSSG value decreased significantly.6.Under waterlogging stress,the lactic acid fermentation in 'xin ai qing' was weaker than 'xin xia qing 2',while the ethanol fermentation is opposite,resulting in the accumulation of lactic acid in 'xin xia qing 2' roots was more than 'xin ai qing' and the cytoplasmic acidification was more serious to reduce waterlogging tolerance.The amplification of Hydrogen Peroxid content(H2O2)and the producing rate of superoxide anion radical(O2-)in 'xin ai qing' roots was below the 'xin xia qing 2'.And the abscisic acid(AsA)content,glutathione(GSH)content,ascorbic acid peroxidase(APX),dehydroascorbic acid reductase(DHAR),glutathione reductase(GR)activity in roots of'xin ai qing' seedlings were higher than 'xin xia qing 2' at the same period of waterlogging stress,while the dehydroascorbic acid(DHA)content and oxidized glutathione(GSSG)content of 'xin ai qing' seedlings below the 'xin xia qing 2';the AsA/DHA value and GSH/GSSG value of 'xin ai qing' was lower than the 'xin xia qing 2',indicating that during the period of stress,'xin ai qing' can maintain a higher AsA-GSH circulation efficiency and effectively inhibit the accumulation of H2O2,which may be the one of important reasons for its strong resistance to waterlogging.