Response Of Different Genotypes Of Chinese Cabbage To Exogenous Silicon Under High Temperature Stress

In this experiment,Hoagland nutrient solution hydroponic method was used.Using Na₂SiO₃·9H₂O as the silicon source.Based on the identification of silicon sensitivity of different genotypes of Chinese cabbage?Brassica campestris L.ssp.pekinensis?,different sensitive varieties were selected to study the growth and some physiological characteristics of Chinese cabbage under high temperature stress.Chinese cabbage cultivation provides reference for summer cultivation.The main findings are as follows:1.The growth of different genotypes of Chinese cabbage increased with the increase of silicon concentration in nutrient solution.It increased first and then decreased.It was suitable for 1.2 mmol/L.When it reached 1.8 mmol/L,growth was inhibited,but different genotypes.There were significant differences in the growth,silicon content and leaf pigment content of Chinese cabbage under the same silicon level.Through cluster analysis,Chinese cabbage was divided into three types:silicon-sensitive,insensitive and intermediate.Among them,the silicon-sensitive varieties were Fushan and Fengkang 7789,and the silicon-insensitive varieties were Degao No.1 and Degao No.8.2.The addition of proper amount of silicon in nutrient solution promoted the growth of different silicon-sensitive Chinese cabbage varieties,but the performance of silicon-sensitive varieties was more prominent,such as the concentration of silicon in'Fushan'and'Degao 1'Chinese cabbage.The growth under 1.2 mmol/L increased by 37.2%and 2.24%,respectively,compared with no application of silicon.Under the conditions of day and night temperature of25/18°C,32/25°C and 39/32°C,the fresh weight of'Fushan'treated with silicon was increased by 39.4%,25.5%and 54.8%,respectively.'Degao 1'increased by 4.9%,2.2%and-3%respectively.3.Under the conditions of day and night temperature 32/25°C and 39/32°C,the thermal damage index of 1.2 mmol/L silicon-treated'Fushan'Chinese cabbage was 5.1 and 12.4,respectively,which was 75.18%and 76.69 lower than that without silicon treatment.The heat damage index of'Degao 1'silicon treatment was 10.34 and 20.83,respectively,which was51.1%and 44.9%lower than that of silicon treatment.4.Under the conditions of day and night temperature of 25/18°C,32/25°C and 39/32°C,the silicon content of 1.2 mmol/L silicon-treated'Fushan'Chinese cabbage leaves increased by 43.6%and 33.9%,respectively.And 43.7%,'Degao 1'increased by 21.7%,26.2%and47.6%.The contents of N,P and K in the leaves of Chinese cabbage had similar changes with the silicon content.For example,the nitrogen content in the leaves of'Fushan'Chinese cabbage treated with silicon was increased by 15.7%,0.68%and 16.1%.The application of silicon in nutrient solution can improve the photosynthesis rate of Chinese cabbage leaves under high temperature stress,especially in silicon sensitive varieties.For example,at day and night temperatures of 25/18°C,32/25°C and 39/32°C,the Pn of 1.2mmol/L silicon-treated'Fushan'Chinese cabbage was increased by 15.9%,14.1%and 12.2%;'Degao 1'cabbage increased by 3.6%,6.1%and 5.2%;the Tr,WUEI and Gs of Chinese cabbage leaves increased first and then decreased with the increase of temperature,but Silicon application can effectively reduce the reduction ratio.For example,at day and night temperature of 39°C/32°C,the Tr of 1.2 mmol/L silicon-treated'Fushan'and'Degao 1'Chinese cabbage leaves are higher than those without silicon treatment.53.5%and-2.4%.Under high temperature stress,the application of silicon in nutrient solution can significantly increase the antioxidant enzyme activity and reduce the MDA content of Chinese cabbage.For example,at day and night temperatures of 25/18°C,32/25°C and 39/32°C,the SOD activity of 1.2 mmol/L silicon-treated'Fushan'Chinese cabbage leaves increased by 0.45%and 2.55%.1.03%,POD activity increased by 7.2%,5.2%and 12.2%,,CAT activity increased by 27.0%,20.5%and 16.4%,and MDA content decreased by 21.4%,22.5%and 2.4%.The SOD activity of'Degao 1'Chinese cabbage leaves increased by 1.15%,0.62%and 1.22%,respectively,and the MDA content decreased by 12.9%,11.1%and 13.3%.