Evaluation And The Mechanism Of The Chilling Tolerance Of Germination Ability Of Rapeseed

Rapeseed is one of the world's four largest oil crops,and is the fifth largest crop in China with an annual planting area of 7.52 million hectares.Rapeseed not only provides people with edible oil,but is also a source of protein feed for animal husbandry.Therefore,the development of rapeseed production is of great significance.the Yangtze River Basin is the main growing regions of winter rapeseed.In recent years,rice growth duration was prolonged.The low temperature became the limiting factor of wintering cultivation.Serious chilling caused great damage to winter rapeseed,finally the yield and quality were decreased.As the first stage of plant growth,low temperature will delay seed germination time,decreased seed germination rate,and inhibit the seedling development.So clarifying their physiological mechanism of low-temperature tolerant cultivars is very important.In this experiment,31 different rapeseed varieties with different cold tolerance were used as experiment materials.In the different temperature(CK:22?,LT:10?)conditions,the germination indexes,antioxidant enzymes activity,the content of hormone and osmotic adjustment substance osmotic stress substances such as Pro were measured.The results appear as shown below.1.The results showed that the relative germination rate,germination index,germination potential,vigor index and fresh and dry plant weight were measured at 10?and 22?,respectively.The low temperature could decrease the germination rate and germination index between varieties,but the decrease amplitude of the varieties with cold tolerance was lower,which can maintain a relatively higher germination rate and so on.2.The comprehensive value of these six indexes was evaluated by membership function and principal component analysis,and 31 rapeseed varieties were divided into sensitive type,intermediate type and cold tolerance type,respectively.3.Three rapeseed varieties with different type were selected for germination test at different temperature at 10? and 22?,and physiological and biochemical indexes related to cold tolerance were determined.The results showed that reactive oxygen species(ROS)level increased and activity of antioxidant enzymes such as SOD,CAT,POD,GR and APX were upregulated under low temperature.In addition,the antioxidant enzymes activity of rapeseed with stronger cold tolerance was higher,which indicated that strong cold tolerant varieties could resist the low temperature damage by improving the activity of their antioxidase system.4.ABA was positively correlated with cold tolerance.IAA,ZR and GA3 were negatively correlated with cold tolerance.Under the low temperature stress,the balance of the hormones level in the seedling was broken.In this experiment,the stronger cold tolerance varieties can maintain the higher ABA content and ratio of ABA/IAA,ABA/ZR and ABA/GA3 to resist the low temperature.whichso can creat a normal intracellular metabolism evironment.5.Under the low temperature stress,the content of soluble protein,soluble sugar and proline in rapeseed seeds were increased significantly,which enhanced the capacity of osmotic potential and water retention in the cells,so that the protoplasm could be protected.In this experiment,with the prolongation of low temperature stress,the soluble protein,soluble sugar and proline content and dosage in the varieties with stronger cold tolerance were higher and the dosage was higher,and the content of the sensitive varieties was smaller.