The Study On Dormancy Causes And Physiological Characteristics Of Germination Of Three IIex Purpurea Seeds

The dormancy causes of IIex opaca, Ilex dipyrena Wall, Ilex aquifolium were studied in this thesis through the mensuration of the testa structure and permeability, the observation of embryo growth when seeds were ripe, and the bioassay of the solution extracted from different parts of seeds. In order to find the method for breaking seed dormancy, the seeds were treaded by combination pretreatment of acid scarification, hormones soaking, and stratification. The dynamic changes of some physiological indexes during stratification were also measured to reveal the physiological characteristics of seed germination could be revealed. The results were shown as follows:1. The testa of IIex opaca, Ilex dipyrena Wall, Ilex aquifolium seeds were dense, hard,and severely keratinized. The cells were compactly arrayed in this area, thereby the permeability of testa to gas is poor. The testa of IIex opaca reveals outstanding especially, which may cause some mechanical barrier for the seed dormancy. The permeability to water of Ilex dipyrena Wall and Ilex aquifolium was fine while that of IIex opaca was pool. The observation of seed embryo development and the mensuration of the ratio of embryo length to endosperm length showed that the differentiation of seed embryo was not completed at natural germinate. So the physiological after-ripening was needed before the seeds could germinate. The bioassay of solutions extracted by water or methanol showed that there were germination inhibitions in all parts of seeds, and the order of inhibitory effect was: testa > endosperm (embryo). Among these, the main causes of the dormancy of the three IIex purpurea seeds were the after-ripening of embryo, poor gas permeability and mechanical restraint of seed coat, while the permeability to water and inhibitors were less important in this respect.2. Acid scarification could reduce barriers to seed coats, accelerate the germination and promote the germination significantly, but it can not make seeds sprout earlier. Meanwhile, soaking with GA3 could promote embryo after-ripening, and speed up seed germination. The optimal concentration of GA3 to promote seed germination varies among species. Warm stratification and alternative stratification (day and night) can promote the seed germination, speeding the process of overcoming the seed dormancy.In this experiment, the best treatment obtained for IIex opaca was that soaking with 98% sulpuric acid for 20minutes+100mg·L-1GA3 for 48 hours+ alternative stratification (day and night).The best treatment obtained for Ilex dipyrena Wall was that soaking with 98% sulpuric acid for 30minutes+500mg·L-1GA3 for 48 hours+ alternative stratification (day and night), which could raise germination percentage to 26%. The best treatment obtained for Ilex aquifolium was that soaking with 98% sulpuric acid for 15minutes+500mg·L-1GA3 for 48 hours+ warm stratification.3. During the stratification of IIex opaca seeds, the nutriment metabolism gradually strengthened. As the starch descended and the activities ofα+β-armylase and ACP were also enhanced, indicating that metabolism was accelerated in the seeds.And the activities of G-6-PDH and 6-PGDH and POD were also increased gradually, which were the signs of PPP activation.