| Brassica napus L.(Rapeseed)is the largest oil crop in China.80% of rapeseed is distributed in the rice-oil rotation area in the Yangtze River Basin.With the continuous delay of the rice harvest period and the continuous expansion of the area under the triple cropping system of rice-rice-oil,the planting period of rapeseed in the Yangtze River is constantly delayed.5-hydroxytryptamine(5-HT)and melatonin(Met),as plant hormones,have been widely used to improve plant resistance to drought and salt stress.This study aims to study the effects of 5-HT and Met on the physiological and biochemical characteristics of plants under low temperature stress,which has very important theoretical and practical significance for improving the low temperature tolerance of rapeseed.The main results are as follows:(1)66 rapessed varieties(lines)in 22 ? and 9 ? under the condition of germination experiments,the results showed that 9 ? low temperature will decreased germination vigor,germination rate,germination index,extend the mean germination time,materrials from mid-land were more tolerant than those from north,semi-winter-type lines wre more tolerant than spring-and winter-type materials,conventional varieties were more tolerant than hybrids.In addition,using the method of membership function of 66 rape varieties(or lines)is used to comprehensive evaluation of the low-temperature tolerance,and through the cluster analysis is divided into the following six levels: level ?,extreme low temperature resistant varieties;? level,strong low temperature resistant varieties;? level,low temperature resistant varieties;? level,medium low temperature resistant varieties;? level,low temperature resistant varieties;? level,sensitive varieties.sensitive varieties.H5(hybrid of Qinyou 8 ×e6013)was the extremely low-tempererature-resistant variety,and S10(Huifeng 1)was the sensitive one.(2)The spring hybrids with the composite membership function value of 0.407,cold resistance index of 11.1 and Guanyouza 303 were used as the materials.The seeds and seedlings were pretreated with 0,0.01,0.02,0.03,0.04 g/L of 5-HT and 0,0.005,0.0075,0.01,0.015,0.02 g/L of Met,and then treated with low-temperature stress.The results showed that 5-HT and Met could improve the germination vigor,germination rate and germination index of rapeseed seeds under low temperature stress,and shorten the average germination time.It can improve the survival rate of rapeseed seedlings under low temperature stress.When the concentration of 5-HT and Met was 0.03 g/L and 0.01 g/L,the germination vigor of rapeseed seeds under low temperature stress was increased by 19.1% and 20.9%,respectively,the germination rate was increased by 10.7%,the germination index was increased by 22.2% and 26.7%,the mean germination time was shortened by 1.1 d and 1.2 d,respectively,and the survival rate of rapeseed seedlings under low temperature stress was increased by 75%.Finally,based on the results of germination and seedling stage,the optimal dosage of 5-HT was 0.03 g/L and the optimal dosage of Met was 0.01 g/L.(3)0.03 g/L 5-HT and 0.01 g/L Met treatment of rapeseed seedlings to low temperature stress and CK treatment,at the same time sampling of osmotic regulation substances(SS,SP,PRO)content,membrane lipid peroxidation products(MDA)content and antioxidant enzymes(CAT,POD,SOD)activity and the low temperature stress response gene(CBF,COR)expression of quantity analysis.The results showed that under low temperature stress,compared with CK,5-HT and Met could significantly increase the content of osmotic regulatory substances,significantly reduce MDA content,significantly increase the activities of CAT,POD and SOD,significantly increase the expression of SOD gene and the expressions of COR6.6,COR15 and CBFs.And based on the above research results,speculated that exogenous 5-HT and Met by increasing osmoregulation substances(SS,SP,PRO)content,antioxidant enzyme system(CAT,POD,SOD)activity and transcription,reduce the membrane lipid peroxidation products(MDA)content,promote the expression of CBF,COR,thus improve the rapeseed tolerance to low temperature stress. |
PDF Full Text Request