Cold Resistance Research Of Abscisic Acid On Winter Rapeseed (Brassica Rapa L.) In North China

For winter rapeseed are vulnerable to the low temperature freezing injury in the northern China, where the wether is characterized with cold in winter, the experiment was conducted to analysis the effects of exogenous abscisic acid spraying on winter rapeseed(Brassica rapa L.)seedling physiology response, photosynthetic characteristics under low temperature, and growth and development characteristics, over-wintering rate, cold resistance and yield by taking Brassica rapa cv. Longyou6, Longyou7( ultra strong cold tolerant cultivar), Longyou8(strong cold tolerant cultivar) and Tianyou2, Tianyou4(cold sensitive cultivar), Neib(not cold tolerant cultivar) and Brassica napus(Vision, Meiqieshi) as materials and to research effects of endogenous ABA content to cold resistance on Brassica rapa and Brassica napus, developing of cold resistance agent adjust to the winter rapeseed in the northern region, to provide theoretical foundation for safely production and applying exogenous hormones technology to increase cold resistance of winter rapeseed in north China. Specific results are as follows:1. In north China, folar spraying exogenous ABA can improve cold resistance by increasing the activities of protective enzyme(SOD, POD, CAT) and content of osmotic regulation(SP, SS, Pro) of winter rapeseed at low temperature stress, reduce the MDA content and membrane permeability and resist cold by increasing the collar diameter, the weight of roots and the number of lateral roots, finally, improving wintering rate and cold resistance.2. The appropriate spraying period and concentration of foliar ABA for mitigating of low temperature injury to winter rapeseed was selected, which, the effects of six leaf stage sprayed 20 mg/L exogenous ABA was excellent, and the over wintering rate is highest(86.3%), which improve 26.7% than CK.3. Spraying ABA can significantly improve content of photosynthesis pigment which mainly include chlb and carotenoid after low temperature stress(-5℃). And that spraying ABA can increased stomatal aperture and ratio of aperture stomata to result in the Pn, Gs, Ci improved remarkably. It also can stimulate rooting which contribute to the weight of roots by increasing the collar diameter and the number of lateral roots and the root/shoot ratio increased. Keeping the roots have exuberant vitality to maintain the status of roots continue to grow at low temperatures by increasing root activity. These all contribute to the wintering rate improved 15.3%~39.5%, and the weak cold resistance have more potential to improve the wintering rate, and finally improved yield and economic coefficient.4. Five types of cold resistance agent(T1: distilled water(CK); T2:20 mg/L ABA; T3:20 mg/L ABA+300 mg/L PEG-6000; T4:20 mg/L ABA+50 mg/L PP333; T5:20 mg/L ABA+300 mg/L PEG-6000+50 mg/L PP333; T6:20 mg/L ABA+300 mg/L PEG-6000+50 mg/L PP333+10 g/L Co(NH2)2) all can increase over-wintering rates of winter rapeseed Brassic rapa, and the over-wintering rate of T5 reached the highest(91.97%), which increase18.87% compared with ck. The root collar diameter, branches, pods per plant, yield of per plant, economic coefficient, and yield all increased significantly.5. There is different response mechanism for endogenous ABA content between winter rapeseed Brassica rapa and Brassica napus in low temperature stress, this effect resulted to the chlorophyll contents of Brassica rapa lower than Brassica napus, the wilt leaf date of Brassica rapa comes and go into the wintering stage in advance, increased the resistance to low temperature and avoidanced of low temperature freezing injury. So, the endogenous ABA content increased after low temperature stress is the main reason that result leaf wilting period come in advance of winter rapeseed Brassica rapa and have strong cold resistance than Brassica napus.