Effect Of Exogenous Spermidine On Longzi Black Highland Barley In Saline Alkali Environment The Impact Of Physiological Metabolism And Dry Matter Formation

Longzi black highland barley has high nutritional value and has been widely favored by the public in recent years.However,the saline-alkali environment in Longzi County,the main production area of black highland barley,severely restricts the production of black highland barley.As a polyamine substance,spermidine can effectively alleviate the damage caused by the saline-alkali environment to crops,significantly improve the photosynthetic performance of leaves,actively regulate dry matter transport,and increase crop yield.Based on this,this experiment was mainly conducted in Longzi County,Tibet,focusing on the effects of exogenous spermidine on the growth and physiological characteristics of black highland barley seedlings under salt and alkali stress,as well as the effects of exogenous spermidine on physiological metabolism and dry matter formation of black highland barley after flowering under salt and alkali environments.The purpose is to provide technical support for promoting the industrialization of black highland barley in Tibet and for local rational spraying of exogenous spermidine to alleviate the damage caused by the saline and alkaline environment.The main results of the experimental study are as follows:（1）When the seedlings of black barley were sprayed with exogenous spermidine under saline-alkali stress,the chlorophyll content and relative water content of the seedlings increased significantly,and the photosynthetic capacity was significantly enhanced;The activities of peroxidase and superoxide dismutase were significantly increased.The contents of soluble protein and proline increased significantly,while the relative conductivity and malondialdehyde content showed a downward trend.Above-and below-ground biomass has increased significantly.This showed that exogenous spermidine could reduce the damage of saline-alkali stress to black barley seedlings.（2）Spraying exogenous spermidine helps to alleviate the damage of saline-alkali environment to black barley leaves,which is conducive to the improvement of photosynthesis.Compared with the control S1（spraying water）,the photosynthetic indexes were improved to different degrees at each time point after flowering,and the treatment with different concentrations of exogenous spermidine was better overall.Based on the photosynthetic physiological indexes of Longzi black barley,the concentration was 750μmol·L^-1has the best S4 treatment.（3）Spraying exogenous spermidine can regulate the distribution of dry matter in various periods of black barley and improve the distribution ratio of vegetative organs in saline-alkaline environment.Exogenous spermidine spraying can effectively regulate the dry matter storage level of leaves during the flowering period,and reduce the dry matter accumulation and distribution rate of stems,sheaths and ears.Exogenous spermidine spraying can reduce the proportion of dry matter distribution in mature vegetative organs and increase the proportion of grain distribution.Furthermore,the spraying of exogenous spermidine can improve the damage of the saline-alkali environment to leaves,change the pre-distribution ratio,increase the post-flower assimilation,and increase the contribution of post-flower assimilation to the grain.The comprehensive results showed that S4 and S5 treatments had the most obvious effect compared with S1 in regulating the distribution ratio of dry matter in various periods.（4）Spraying exogenous spermidine can increase the plant height,effective panicles,grains per panicle,thousand-grain weight,and yield of black highland barley in saline and alkaline environments to varying degrees.Among them,S3,S4 and S5 treatments performed better,with yields increased by 29.97%,31.23%and 24.92%compared to control S1,respectively.