Regulation Of Germination And Growth Of Suaeda Salsa Under Combined Stress Of Salt And Heavy Metal

Suaeda salsa,a common dominant species in coastal wetland,plays a great role in ecological protection,including the modification of soil physical and chemical properties,water purification,biodiversity maintenance,etc.However,massive death of Suaeda salsa was found due to severe damages to its growth environment by various reasons such as soil salinization,heavy metal pollution and so on.This paper explored the suitable agents and optimal treatment conditions for Suaeda salsa germination by treating the seeds of Suaeda salsa with two kinds of agents——oxidant and phytohormone,at different concentrations and treatment time.Through the orthogonal experiment to explore Zn,Cu and salt under combined intimidation of Suaeda salsa germination and growth,the influence mechanism.In addition,the paper,treating the seed of Suaeda salsa with three suitable agents——KNO₃,GA and IAA in optimal conditions,studied the regulation effects of the three treatment measures on the germination and growth of Suaeda salsa under the combined stress of Zn,Cu and salt.The results showed that:（1）Both the oxidant and the phytohormone could promote the germination of Suaeda salsa seeds.Compared with CK,the germination percentage and germination speed of seeds treated by KMn O₄,H₂O₂and KNO₃ increased by 13.73%and 25.02%,17.65%and41.64%,17.65%and 77.39%,respectively,under the optimal conditions.The germination percentage and germination speed of seeds treated by GA,IAA and KT increased by 20.00%and 79.60%,17.65%and 136.84%,9.80%and 55.79%,respectively.（2）The concentration of agents was the main factor to promote the germination of Suaeda salsa seeds,and the appropriate concentration could significantly improve the germination percentage and accelerate the germination process.Effects of different agents on seed germination of Suaeda salsa under the optimal treatment conditions is IAA>GA>KNO₃>H₂O₂=KT>KMn O₄.Prolonging the treatment time of oxidant and phytohormone had no obvious effect on the germination percentage of Suaeda salsa seeds,and even caused the seed germination speed to decrease.（3）The germination of Suaeda salsa was more obviously inhabited by the combined stress of salt and heavy metals than single stress.The combined stress of Zn,Cu and salt in different concentrations showed significant differences in affecting the germination percentage and germination speed of Suaeda salsa seeds.The single Zn and Cu stress had little effect on the germination of Suaeda salsa,but Zn and Cu significantly enhanced the stress effect of salt on Suaeda salsa seeds.（4）Suaeda salsa responded to the combined stress of salt and heavy metals by increasing the contents of proline,soluble sugar and soluble protein.Proline showed maximum efficacy in maintaining the balance of cells.At the same time,with the increase of salt concentration in the compound stress,the activities of three antioxidant enzymes in Suaeda salsa increased first and then decreased.The CAT activity decreased most obviously under combined stress of Zn,Cu and high salt,which brought Suaeda salsa with severest damages that were beyond the regulation capacity of the soluble protein,soluble sugar and three antioxidant enzymes.（5）KNO₃,GA and IAA treatments had different effects on seed germination under combined stress.With the increase of salt concentration in combined stress,three treatments gradually enhanced the promotion effect on seed germination percentage and germination speed.Treatment by 100 mg/L GA,1.5 mg/L IAA and 0.3%KNO₃ displayed the most obvious increase in the germination percentage under the combined stress of low Zn,high Cu and high Na Cl,low Cu,high Zn and high Na Cl,medium Zn,medium Cu and high Na Cl.1.5 mg/L IAA treatment significantly promoted the germination of Suaeda salsa seeds under combined stress of various concentrations of Zn,Cu and salt stress.（6）The three treatments mainly increased the content of soluble protein and soluble sugar to cope with the combined stress of Zn,Cu and Na Cl.Among them,KNO₃ treatment mainly increased the content of soluble protein,IAA treatment mainly increased the content of soluble sugar,while GA treatment mainly increased the content of soluble protein and soluble sugar.All the three treatments could increase the activities of antioxidant enzymes,and the activities of SOD,CAT and POD were different in KNO₃,GA and IAA treatments under the combined stress of various concentrations of Zn,Cu and salt.