Research Of CaCl₂ On Drought Resistance Mechanism Of Cotton

This study adopted the indoor soil culture,water planting and field pot culture method respectively,used drought-resistant variety Yumian-19 and water sensitive variety GK20 and control variety Lumianyan-28 applied in the production as the materials,set the drought,drought+20mmol/L CaCl₂,drought+40mmol/L CaCl₂,drought+80mmol/L CaCl₂ treatment.The drought treatment was set as control?CK?,indoor nutritional soil culture used 10% PEG-6000 drought stress simulation treatment,indoor water planting set 15% PEG-6000 drought stress simulation treatment,and the field pot experiment controlled the relative soil water content of 45%-55% as the drought treatment.Through the analysis of CaCl₂ treatment on changes in agronomic characters,cytological characteristics and related physiological indexes of different varieties of cotton in different periods under drought stress,the influence of CaCl₂ on drought resistance of cotton was studied.The main results were as follows:1.Influence of CaCl₂ treatment on the agronomic characters of cotton under the drought stress.This study mainly measured the germination potential,germination rate,fresh weight,dry weight,water content,plant height,root length and SPAD values of cotton treated by different concentration of CaCl₂ under drought stress.Results showed that compared with CK,20mmol/LCaCl₂ treatment could obviously improve the germination potential and germination rate of cotton under drought stress,fresh weight,dry weight,water content,plant height and root length of cotton seedlings.It also can significantly improve the fresh weight,dry weight,water content,plant height and SPAD values of GK20 in the seedling stage and bud stage.Compared with CK,40mmol/LCaCl₂ treatment can significantly improve fresh weight,dry weight,water content of Yumian-19 and Ruyanmian-28 under drought stress,plant height in the bud stage,and SPAD value in the seeding stage and bud stage.80mmol/L CaCl₂ treatment aggravated the stress on the cotton.2.Cytological characteristics of cotton root system treated by different concentration of CaCl₂ under drought stress.This study mainly measured the total root length,root surface area,total volume of root of cotton treated by different concentration of CaCl₂ under drought stress,and microscopic observation was conducted on various treated root transverse sections.Results showed that compared with CK,20mmol/L CaCl₂ treatment can significantly improve the total root length,root surface area,total volume of root volume and developed root system of cotton under drought stress.We found through root slice observation that the root transverse section of GK20 treated by 20mmol/LCaCl₂ kept round,with minimum cortex water loss deformation degree and developed xylem,and it was least influenced by drought stress,while Yumian-19 and Ruyanmian-28 treated by 40mmol/L CaCl₂ were influenced by drought stress.But cortical cells of root system treated by 80mmol/L CaCl₂ invaginated due to water loss,and the serious shrinkage deformation phenomenon occurred in root system.3.Influence of CaCl₂ treatment on the physiological indexes of cotton under drought stress.This study mainly measured SOD and POD activity,proline and MDA content of cotton treated by different concentration of CaCl₂ under drought stress cotton.Results showed that compared with CK,SOD and POD activity,proline content of GK20 treated by 20mmol/L CaCl₂ were increased significantly,MDA content was decreased significantly,so the concentration was optimal for GK20;SOD and POD activity,proline content of Yumian-19 and Ruyanmian-28 treated by 40mmol/LCaCl₂ were increased significantly,MDA content was decreased significantly,so the concentration was optimal for Yumian-19 and Ruyanmian-28;SOD,POD activity and proline content treated by 80mmol/L CaCl₂ were significantly lower than those of CK,MDA content was significantly higher than that of CK,so the stress aggravated.The difference of different treatment of pot experiment from 6d was significant and SOD,POD activity and proline content increased at first and decreased subsequently with the drought time,while MDA accumulation increased gradually,showing that CaCl₂ treatment effect gradually weakened when the degree of drought was too high.To conclude,CaCl₂ treatment can reduce the influence of drought stress on cotton growth and development within a certain range,and its mechanism is that exogenous calcium promotes cotton seed germination,improves the growing potential,makes root system developed,can absorb enough water and nutrient under dry conditions to maintain growth,inhibits membrane lipid peroxidation reaction,maintains the stability of cell membrane structure,reduces the membrane damage,and improves the drought resistance of cotton.