A Preliminary Study On Seed Dormancy Characteristics And Germination Physiology Of Cyclocarya Paliurus (Batal.) Iljinskaja

Cyclocarya paliurus seeds germinate on the second year or the third year in nature, belonging to a type of comprehensive deep dormancy. In this study the dormancy characteristics of Cyclocarya paliurus seeds are studied through experiments such as morphological dissecting of the seeds, the seeds coats microstructure under the scanning electron microscope, the water absorption of seeds coats and the biotic measurement of the methanol extract of Cyclocarya paliurus seeds coats. The quick dormancy-breaking techniques of Cyclocarya paliurus seeds are studied through two kinds of treatments. One treatment is soaking the seeds in concentrated sulphuric acid first, soaking the seeds in GAs 48 hours, and then stratifying seeds under different temperatures. The other treatment is stratifying seeds under natural temperatures. And during the stratification treatment, the content of starch , the content of soluble sugar, the content of endogenous hormones and the activity of the amylase in the seeds are measured to find out the germination physiology of Cyclocarya paliurus seeds. The results are as followings.Three layers are found in the seed coat of Cyclocarya paliurus under the scanning electron microscope: external seed coat, mid seed coat, and inner seed coat. The epidermis of external seed coat is cutinized, and the mid seed coat is phellem, and the inner seed coat is lignified and hard. All these characteristics show a big hindrance and permeability barrier in the seed coat of Cyclocarya paliurus, preventing the water and gas from exchanging and resulting in blocking the water absorbing and germinating of the seed. And the result of water absorption of seeds coats show that seeds which are treated by concentrated sulphuric acid absorb water more quickly than the control seed do. The water consent of the seeds shows that the embryos of untreated seeds also absorbed some water in the water absorption experiment. So the mechanical restraint of the seed coat which restrain radicel growing is one of the main reasons to cause the seed dormancy of Cyclocarya paliurus.The biotic measurement results of the methanol extract of Cyclocarya paliurus seeds coat show that the methanol extract contains some germination-restrauiing substance which could reduce cabbage seed germination and simplified vigor index(SVI),and suppress seedling and root growth, especially at high concentration treatment.. This result shows that some germination-restraining substances in Cyclocarya paliurus seeds coat could result in the dormancy of the young embryos.During seeds stratification under different temperatures to break dormancy, the content of abscisic acid (ABA) in the Cyclocarya paliurus seeds reduces gradually, but the contents ofgibberellic acid (GA),indole-3-acetic acid (IAA) and cytokinin (CTK) increase at the same time, and the ratios of gibberellic acid (GA)/ abscisic acid (ABA), indole-3-acetic acid (IAA)/ abscisic acid (ABA), cytokinin (CTK)/ abscisic acid (ABA) increase ultimately. The results of the experiments make sure that GA promotes seeds germination and that indole-3-acetic acid (IAA) and cytokinin (CTK) affect the seeds germination too. During seeds stratification under nature temperatures, the total activity of the amylase increases, amylolysis accelerates, the content of starch reduces, the content of soluble sugar increases continuously, and the content of soluble sugar in the stratified seeds is more than in the control seeds.