| Taxus var.mairei is a variety of Taxus in the Taxaceae family.It is a national first-class key protected wild plant that integrates medicinal,material and ornamental value.T.chinensis var.mairei seeds have the characteristics of deep dormancy,under natural conditions need to go through two winters and one summer to germinate normally,untreated morphologically mature seeds need more than one year of layered germination to relieve dormancy,germination rate is low and uneven.In this study,the physiological characteristics of the seed after-ripening process were studied in view of the actual problems in the development of T.chinensis var.mairei plantations,and the physiological mechanism of T.chinensis var.mairei seeds ripening was grasped through the analysis of changes in seed morphology,nutrient content,enzyme activity and endogenous hormone content.Based on this guide,the medium and hormone combination of vitro culture of T.chinensis var.mairei embryos were systematically optimized,and tissue culture technology was used to solve the practical problems of low seed germination rate and difficult seedling breeding.The main findings are as follows.(1)Changes in morphology and structure of T.chinensis var.mairei seeds during after-ripening.T.chinensis var.mairei seeds are mostly oval in shape,a few are tapered,and the seed umbilicus is oval or triangular.The outer seed coat of freshly harvested seeds is tan,the surface is smooth,hard and dense,the seed embryo is white,the structure is complete,and the volume is small.After one year of layered sand,the outer seed coat of the seed deepens to black,the tip of the seed coat cracks,and the color of the seed embryo changes to pale green.The seed germination rate is zero when first harvested and can reach 10.76%after one year in stratification sand storage.There were no significant differences in seed diameter,seed longitudinal diameter and seed thickness at different layering stages.It was found that the length and width of seed embryos varied significantly during the process of layered sand,and the embryo body continued to increase,and the embryo body developed from the initial near-spherical embryo to a mature cotyledon embryo.(2)Changes in the physiological and biochemical properties of T.chinensis var.mairei seeds during post-maturation.Seed stratification during sand storage.The soluble sugar content decreased in the early stage and gradually increased with the increase of lamination time;the soluble protein content showed a continuously increasing trend throughout the lamination time,increasing 3.8 times(43.39 mg·g-1)compared with the stratification sand storage.The starch and fatty substance contents continued to decrease,and the contents decreased to 1.07%and 33.54%respectively after sand storage.Peroxidase activity increased and then decreased,and after one year of sand lamination,peroxidase activity was still higher than before lamination,being 6.03 times higher(1117.50 μg · g-1·min-1)than before the start of sand lamination.Abscisic acid(ABA),cell growth hormone(IAA),cytokinin(CTK)and gibberellin(GA3)levels did not change consistently during the different periods of stratification sand storage,with different hormone species showing significant increases or decreases to different degrees.(3)T.chinensis var.mairei seed embryos were cultured in vitro.Based on the dynamic changes of nutrient and hormone contents during seed post-maturation,T.chinensis var.mairei seed embryos from 12 months of stratification sand storage were subjected to in vitro culture,and the formula of T.chinensis var.mairei seed embryos in vitro culture was optimal when WPM medium+6 mg/L GA3+0.10 mg/L KT.The seedling germination rate of seed embryo culture could reach 66.67%.The seed embryo isolation culture could significantly improve the seedling germination rate of T.chinensis var.mairei.The results show that the shape of the seeds during the ripening process of T.chinensis var.mairei seeds.There were significant changes in state,structure and nutrient content,enzyme activity and endogenous hormone content,which promoted the release of seed dormancy.After stratification sand storage,the germination rate of T.chinensis var.mairei seeds was still very low.In combination with subsequent in vitro culture of seed embryos,the seedling growth rate of T.chinensis var.mairei seeds can be significantly improved,which is an effective way to solve the problem of T.chinensis var.mairei seedling propagation. |
