Effects Of Different Degree Of Saline-alkali Stress On Physiological And Biochemical Characteristics Of Rape Seedling

Soil salinization is a widespread environmental problem worldwide,which severely affects the growth and development of crops,limits the quality and yield of crops,and develops economic and ecological benefits of saline-tolerant crop resources that have received increasing attention.This experiment uses Pot experiment,planting rape under complex saline-alkali stress,analyzing physiological and biochemical characteristics of rape seedling growth,osmotic adjustment,photosynthetic parameters,ion transport,etc.,exploring the physiological response mechanism of rapeseed to salt-alkali stress in order to further reveal the salt tolerance of rape The mechanism provides a theoretical basis.The main conclusions are as follows:?1?Effects of different levels of saline-alkali stress on photosynthetic parameters and biomass of rape seedlings.With the increase of the degree of combined saline-alkali stress,the net photosynthetic rate,stomatal conductance and transpiration rate of rapeseed seedlings decreased first and then increased,and intercellular CO₂ showed a downward trend.Compared with the pre-emergence stage,the decline was the largest under severe stress,which were 45.3%,74.9%,46.7%,and 44.2%,respectively.Rapeseed seedlings showed a decreasing root height,Compared with the mild and moderate treatments,the pre-emergence stage was reduced by 25.50%,41.83%,37.04%,and 46.30%;the post-emergence stage was reduced by 21.55%,15.19%,9.09%,and17.05%,respectively.Saline-alkali stress inhibited the increase of photosynthetic parameters and plant height and root length in rapeseed.The degree of inhibition at the early seedling stage was higher than that at the later stage of seedling,and the degree of severe saline-alkali stress inhibition was more obvious.?2?Effects of different levels of saline-alkali stress on soluble sugar and proline content in rape seedlings.With the increase of salinity,the soluble sugar content in the leaves of rapeseed seedlings showed a decreasing trend,in which the late seedling stage was higher than the pre-seedling stage,which were 115.6%,139.8%,and 52.9%of the pre-seedling stage;In order to increase first and then decrease,the post-emergence stage showed a downward trend,and the latter stage was 318.8%,210.1%,and 181.0%of the pre-emergence stage.When rapeseed seedlings were subjected to saline-alkali stress,they showed osmotic stress in the early stage of seedlings,and later in the body began to adapt and accumulate proline and soluble sugar to make corresponding adjustments.?3?Effects of different levels of saline-alkali stress on protective enzyme activities in rape seedlings.With the increase of salinity,the activities of SOD and POD enzymes decreased in the late seedling stage compared with the pre-seedling stage.Activity increased,and the increase was 79.9%,131.1%,2460.3%.Under saline-alkali stress,rape seedlings in the early stage of seedlings can increase their SOD and POD enzyme activities to remove the superoxide anion free radicals and H2O2 produced by stress,while in the later stage of seedlings,they can increase CAT enzyme activity to reduce oxidative damage and adapt its adversity.?4?The effects of saline-alkali stress on ion absorption and transportation in rapeseed seedlings.Under different levels of saline-alkali stress,Na⁺accumulated in the stems and leaves was larger than that in the roots at the early seedling stage,and the contents of the stems and leaves were 45.63,1.02,and 2.63 times that of the roots,respectively.The ratio is larger than the root,and the ratio of Na⁺/Ca²⁺is smaller than that of the root.In the late seedling period,the accumulated Na⁺in stems and leaves is smaller than the root,especially under moderate and severe stress,the ratios of Na⁺/K⁺,Na⁺/Ca²⁺are smaller than the root,and the ratio of Na⁺/Mg²⁺is larger than the root.Under compound saline-alkali stress,the ions in rapeseed seedlings in the early stage of seedlings are distributed regionally,and Na⁺is preferentially accumulated in the stems and leaves to ensure the normal growth of the roots;Na⁺is trapped in the roots in the late stage of seedlings to ensure that other nutrients are transported to the stems and leaves.Maintain ion balance in seedlings.?5?Effects of different levels of saline-alkali stress on soil pH and microbial diversity.When rapeseed grows to the five-leaf stage under salt stress,the pH of the soil decreases compared to before planting;as the degree of saline-alkali increases,the soil bacterial diversity decreases;the structure of the bacterial community significantly increases with the increase of saline-alkali stress The gradient structure of bacterial communities in mild and moderate saline-alkali soils is similar,and the structure of bacterial communities in severe saline-alkali soils is quite different.