Studies On The Relationship Of Gibberellins, Abscisic Acid And Seed Vigor In Maize

The level of seed vigor determines the germination rate, the seedling growth potential and the plant yield and quality. The levels of GA and ABA within seed affect seed germination and seedling growth potential. Maize (Zea mays cv. Zhengdan 958) seeds were used to analyse the contents of GA and ABA in scutellum of fresh, old maize seeds and their isolated embryos, which germinated three days and were different germination states;and tested the activity of antioxidant system enzymes(CAT,POD,SOD)and the contents of free amino acids, soluble sugar, GA and ABA of the embyos with different seed vigor; and tested the influences of GA3 and ABA treatment on seed germination and seed vigor of naturally aged seeds;investigated the realationship of GA, ABA and seed vigor.The main results are represented below.1. The relationship of endogenous GA , ABA and seed vigorAfter the seed soaking, the contents of GA and ABA are significant different among the embryos of the high, low vigor and nonviable of old seeds. The contents of GA and ABA in high vigor embryos are lower than in low vigor embryos; the content of GA in nonviable embryos is highest, and the content of ABA in nonviable embryos is lowest. Nonviable seeds which could not germinate are no correlation with the GA and ABA within the embryos. The contents of GA and ABA in old and viable embryos increase with the seed vigor reducing. After the fresh, old seeds and in vitro embryos germinated 3 days, the contents of GA and ABA have significant difference within the different germination states. The scutellums of seeds and in vitro embryos, which were viable but did not germinate, have the high levels of ABA and low contents of GA. The content of GA in scutella of rapidly germinated embryos is higher than it in scutella of slowly germinated embryos. The contens of ABA in scutella of the germinated embryos are no correlation with the germination rate of the seeds and in vitro embryos.2. The changes of physiological and biochemical characteristics in old seed embryosThe various antioxidant enzymes(CAT,POD,SOD)and the content of free amino acid in old seed embryos reduce with the seed vigor decreaseing; the content of soluble sugar in old seed embryos increases with the seed vigor decreasing.3. The influence of exogenous GA3 and ABA on the old seed's vigorThe series of concentration of GA3 and ABA treat with the naturally aging seeds of maize. Compared with the control, (1) All treatments of GA3 (10~1000mg?L-1) could promote the batch seeds'germination, and significantly increased seed vigor;?in particular, the treatment of 100mg?L-1 GA3 significantly increase seed vigor and promote the aging seeds'germination. (2)?The treatment of 10 mg?L-1 ABA could significantly increase seed vigor, and promote the aging seeds'germination; the treatments of 30~100 mg?L-1 ABA could reduce seed vigor, and the effect on seed vigor index is more significant with the concentrations of ABA increasing. (3) The treatment of T1(10 mg /L GA3/10 mg?L-1 ABA,1:1), T3(10 mg?L-1 GA3/10 mg?L-1 ABA, 2:1)and T6(20 mg?L-1 GA3/20 mg?L-1 ABA,2:1)could significantly improve the seed vigor, but the other treatments has no significant effect on seed vigor.4. The influence of exogenous GA3 and ABA on the old seed's physiological and biochemical characteristicsCompared with the control,?the treatments of 100 mg?L-1 GA3 and 10 mg?L-1 ABA could significantly increase the contents of free amino acids in the embryo; the treatment of T1 and 40 mg?L-1 ABA could significantly reduce the contents of free amino acids. All the treatments could significantly increase the contents of soluble sugar in embryos, the max increment of soluble sugar in embryos is the treatment of 10 mg?L-1 ABA, the second is the treatment of 40mg?L-1ABA, the third is the treatment of T1, and the treatment of 100 mg?L-1 GA3 had the minimum amount.