Effects Of Salt Stress On Growth And Physiological Characteristics Of Salicornia Europaea Seedlings

Salicornia europaea as an annual herbaceous plants of Chenopodiaceae,with a high degree of succulence characteristics of the stem.It is widely studied as one of the most salt tolerant euhalophytes in the world.Its salt tolerance ability is very prominent,with important scientific research value.In this paper,S.europaea produced in the Aiding Lake area of Turpan,Xinjiang were used as the research object,and the effects of different concentration of NaCl treatments on growth and physiological activity changes at different stages were explored by a pot experiment.The main results were as follows:(1)Growth indexes research showed that:the plant height and fresh weight increased first and then decreased with the increase of stress time and salt concentration.The plant growth under the condition of200 and 400 mmol/L NaCl concentration was significantly better than that of other concentrations.Within 7d,the amount of extravasation in the control and 800 mmol/L high salt treatment was higher than that in the other concentrations,after that,which increased with the increase of salt concentration and treatment time.The results showed that under low salt concentration,the cell membrane was less damaged and could maintain good stability.Chlorophyll a,chlorophyll b,total chlorophyll content and chlorophyll a/b with the strengthening of salt stress intensity showed a trend of decrease.(2)Research on water physiological indexes showed that:the relative water content,water potential,free water/bound water ratio decreased with the increase of stress time and salt concentration.While bound water content showed an increasing trend.On the one hand,the plants under low salt concentration had higher relative water content and sufficient water will help dilute the excess salt in the body;on the other hand,when stress time after 35 d,treatment of high salt concentrations in plants had higher ratio of free water/bound water,plant metabolism was strong,resistance was low.(3)Antioxidant enzyme system research showed that:SOD,POD activity decreased first and then increased with salt concentration increased,and the value of 200 mmol/L salt concentration was the lowest.Indicating that the stress of plant under 200 mmol/L NaCl treatment was the lightest,did not need to produce a large number of antioxidant enzymes to eliminate excessive free radicals.The change trend of CAT activity was not consistent with the increase of salt concentration in different stages.Three kinds of antioxidant enzymes were decreased with the extension of treatment time,indicating that the stress time was too long,the activity of antioxidant enzymes would be greatly weakened,leading to cell damage.(4)Organic osmotic regulation substances research showed that:the content of soluble protein,proline and betaine increased with the extension of stress time.The content of soluble protein was not significantly different between control and salt treatment,and the latter increased with the increase of salt concentration.It was suggested that among the response to salt stress,soluble protein played a regulatory role to the smaller,mainly through increased significantly the content of proline and betaine for osmotic regulation,to balance the high concentrations of salt in the body and improve the ability of tolerance.(5)The content of K~+?Na~+and ratio of K~+/Na~+research showed that:the content of K~+?Na~+in the shoots and roots increased with the extension of stress time.With the increased of salt concentration,the K~+in the shoots showed a decreasing trend,the K~+in the roots increased first and then decreased,and the Na~+in the shoots and roots showed a rising trend.The ratio of K~+/Na~+in the shoots and roots decreased with the prolongation of treatment time and the enhancement of salt stress.The plant under 200 mmol/L NaCl treatment had higher content of K~+and ratio of K~+/Na~+in the shoots and roots,which suggested that with that concentration,the nutrient was more balanced and the concentration of ions was stable in plant.In summary,in a view of growth indexes,water physiological indexes and antioxidant enzyme system,organic osmoregulation substances,the vigorous growth of S.europaea had a requirement for salt,the indexes of 200-400 mmol/L NaCl concentration showed a good level,the concentration of 200 mmol/L NaCl was the optimum concentration of growth,without salt or high salt conditions would be a stress to its normal growth.In this experiment,it was shown that the S.europaea was by keeping higher relative water content,reducing water potential,ratio of free water/bound water,while improving bound water content,improving the content of SOD?POD?proline?betaine?K~+these osmoregulation substances and ratio of K~+/Na~+to tolerate high salt stress.The growth status and water physiological condition of S.europaea showed that it had strong salt tolerance.