Effects of NaCl on Photosynthetic and Physiological Properties of Ribes meyeri Maxim
In order to explore the response mechanism of Ribes meyeri Maxim under salt stress,the chan-ges of photosynthetic fluorescence and physiological characteristics of Ribes meyeri Maxim under salt stress were explored.Five groups of 4-year spring cup cuttings were watered with 0 mmol/L,200 mmol/L,400 mmol/L,600 mmol/L and 800 mmol/L NaCl solutions and the main response substances under salt stress were analyzed by measuring the changes of plant height,root-shoot ratio,ground diame-ter,photosynthetic fluorescence parameters and physiological indexes of salt tolerance in the leaves of Ribes meyeri Maxim.The results showed that with the increase of salt stress concentration and stress days,the plant height increment showed a decreasing trend,the amplitude of the 400 mmol/L and 600 mmol/L treatments was larger,the root-shoot ratio showed a trend of first increasing and then decreasing,and then increasing and then decreasing,while the ground diameter increment showed a trend of first decreasing,then increasing and then decreasing,all of which changed significantly in the 600 mmol/L treatment.The net photosynthetic rate(Pn),transpiration rate(Tr)and stomatal conductance(Gs)all showed a down-ward trend,while the intercellular CO2 concentration(Ci)decreased first and then increased,and the maxi-mum photochemical quantum yield(Fv/Fm),potential photochemical efficiency(Fv/F0),photochemical quenching coefficient(qP)and PSⅡ showed a downward trend.When the NaCl concentration exceeded 600 mmol/L on the 6th day of treatment,the rate of the four fluorescence indexes decreased significantly,and the maximum fluorescence yield(Fm)increased first and then decreased,reaching the lowest value on the 9th day of 600 mmol/L treatment.The non-photochemical quenching coefficient(qNP)showed an upward trend,and the content was at the lowest value on the third day of 400 mmol/L treatment.The ac-tivities of soluble protein(SP),soluble sugar(SS)and free proline(Pro),malondialdehyde(MDA),super-oxide dismutase(SOD)and catalase(CAT)all showed an upward trend,and the content of osmotic regu-lators accumulated significantly on the 6th day of 600 mmol/L treatment,and the activities of soluble sug-ar,proline,SOD reached the maximum.When the treatment exceeded 600 mmol/L,the activities of SOD and CAT in the seedlings decreased significantly,and the increase of malondialdehyde(MDA)content did not change significantly.Peroxidase(POD)activity showed a decreasing trend.Overall,salt stress de-stroyed the photosynthetic mechanism of Ribes meyeri Maxim,and inhibited the net photosynthetic rate,stomatal conductance,transpiration rate,maximum photochemical quantum yield,potential photochemical efficiency.The photochemical quenching coefficient and the actual photoquantum efficiency reduced the u-tilization rate of light energy,resulting in the decrease of photosynthetic and fluorescence rates;The adapt-ability of Ribes meyeri Maxim was mainly alleviated by increasing the content of osmotic regulators and increasing the activity of antioxidant enzymes,thereby improving the adaptability to salt stress;Ribes mey-eri Maxim showed stronger adaptability and stronger salt tolerance under salt stress,and its salt concentra-tion was greater than 600 mmol/L NaCl treatment.In that case it displayed obvious symptoms of victimi-zation.
Ribes meyeri MaximNaCl stresslight and fluorescence parametersgrowth physiological characteristics
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