Response Of Drought Stress To Physiological Mechanism And Drought Resistance Evaluation Of Yellow Seed Rapeseed In Tibet

Rapeseed is one of China’s important crops,but also the main oil crop,occupies a very important position in China’s oil market,for China’s agricultural development has played an irreplaceable role.Yellow seed rape is a unique rapeseed variety in Tibet and is widely distributed in Tibet.Drought is one of the main reasons restricting the development of rapeseed in China,especially the low annual average rainfall in Tibet,which directly affects the production of rapeseed in Tibet.Therefore,it is very important to understand the drought resistance of rapeseed and master the drought resistance mechanism of rapeseed.In this study,24 pieces of cabbage-type yellow rapeseed rape from different regions of Tibet were selected to explore the effects of different concentrations of PEG-6000 solution on the germination of yellow seed rape,determine the suitable concentration,and evaluate the drought resistance of all the participating varieties by using the relative value of suitable concentration.Ten yellowseed rapeseed with strong drought resistance were selected for drought treatment at seedling stage,and the effects of drought stress on photosynthetic indexes and physicochemical indexes at seedling stage were explored.According to relevant data indicators,the most drought-resistant yellow seed rape varieties were evaluated.The main conclusions of this paper are as follows:1)PEG-6000 simulates the germination characteristics and drought resistance evaluation of yellow seed rapeseed under drought stress.Through the analysis of the relative germination rate,relative germination potential,germination drought resistance index,relative bud length,relative root length,relative total length,relative root-to-head ratio,and relative fresh weight under the concentration treatment of different concentrations of PEG-6000 solution,it was concluded that the yellow seed rape variety from Longdan Village had the strongest drought resistance,the yellow seed rape variety from Baijusi No.2 had the worst drought resistance,and the rest of the varieties were in between.2)Effects of different drought degrees on the physiology of rapeseed seedlings.According to the results of comprehensive evaluation of drought resistance during the germination period of yellow seed rape,10 Tibetan cabbage yellow seed rape with excellent drought resistance were selected.The drought resistance of the varieties at the germination stage was evaluated by comparing the relative water content,chlorophyll content,soluble protein content,superoxide dismutase activity（SOD）,peroxidase activity（POD）,malondialdehyde content（MDA）,and free proline content（PRO）of the test varieties,and the final results were sorted according to the drought resistance:variety in Zhanang County>Qiangbainsi variety>Jiding Village variety>Zangyou No.3>Chaya varieties>Nimu County varieties>Qusong rape varieties>Longdan village varieties.3)Through the comprehensive drought resistance analysis of four indexes,including stomatal conductance,transpiration rate,intercellular CO₂ concentration and net photosynthetic rate,the results showed that varieties in Chaya County>varieties in Zhanang County>varieties in Nimu County>varieties in Longdan Village>Zangyou No.3>varieties in Qusong County>varieties in Qiangbain Temple>varieties in Jiding Village.