Desiccation Sensitive and Ultrastructure of Five species of Tree seeds

• Main Authors: CHO, CHUAN-HSIU, 卓娟秀
• Other Authors: KUO-HUANG, LING LONG
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/38277867831361654490

碩士 === 國立臺灣大學 === 植物學系研究所 === 86 === Abstract Artocarpus heteroqhyllus Lam., Machilus japonica var. kusanoi Hayata, Cyclobalanopsis glauca (Thunb.) Oerst, Litsea a cuminata (Blume) Kurata and Leucaena leucocephala Lam. are five woody species distrributed in the low forests of Taiwan. This thesis investigated their seed morphology and the anatomical characteristics, including the composition of i nsoluble storage materials, the ultrastructure of plumule and apex of radicle of the embryo axes. Besides the effects of desiccation on the seed viability a nd the ultrastructure of embryo axes were studied. The results showed that Art ocarpus has the biggest seed mass, however, the size of its embryo axes is sim ilar to that of Leucaena. Among the five species the seed of Leucaena is the s mallest one. With the exception of Cyclobalanopsis, all the other embryo axes in matured seed are full-grown andgenerally with 4-6 primary leaves. In the c otyledons and embryo axes of the seeds of Machilus, Cyclobalanopsis and Litsea there are secretory mucilage or oil cells. The seeds of Artocarpus obviously contain laticifers in the cotyledons and embryo axes. However, tannic cells ar e ubiquitously distributed in the cortex and epidermis of embryo axes, primary leaves and root caps of the seeds. The predominant compositions of insoluble storage materials in the seeds of these five species are starch grains, protei n bodies and oil droplets. The starch grains are distributed in the ground tis sue of embryo axes of Artocarpus , Machilus and Litsea.. The oil droplets are located in the cytoplasm of the cells of embryo axes and in the marginal areas of the cells of plumule and radicle apex. Nevertheless, in the seeds of Leuca ena, the oil droplets are mostly observed around the proteins bodies in the pe ripheryn of the cells in he embryo axes.The highest and lowest moisture conten ts of mature seed are fong in Artocarpus (61.03%) and Leucaena (6.7%) respec tively, and the rates of germination are 60% (Artocarpus ) , 95.04% (Machilus ), 96% (Cyclobalanopsis ), 93.33% (Listea) and 94% (Leucaena）. When the seeds were lost dehydrated 6% (Artocarpus ), 7.5% (Machilus), 17% (Cyclobalanopsis) , 35% (Lacumunata) of their moisture contents by the saturated lithium chlorid e (LiCl), the rate of germination decreased dramatically. Among the five woods , the seed of Lacumunata are the most resistant to low temperature storage (4 0C) and seed of Artocarpus are more susceptable to low temperature treatment. These results suggest that the degrees of desiccation susceptibility of these seeds are Artocarpus, Machilus, Cyclobalanopsis, Litsea and Leucaena. The ultr astructural study on the seeds showed the cells of plumule and radicle apex ha s dense cytoplasm, and a large nucleus occuping 20-30% of the cell volumn. The size of vacuoles in the cytoplasm widely varies with the species. In the cyto plasm of Leucaena, the mitochondria, endoplasmic reticulum and plastids are se ldom observed, however, in other species these organelles are ubiquitous distr ibuted and metabolic active. During the drought stress, the seed coat, cotyle don and embryo axes are obviously shrunk. The ultrastructural change in the ce lls of plumule apical meristem are fusion or lysis of tonoplast, deformation o f nucleus and nucleolus, shrinkage of protoplasm, and formation of small vesic les in the cell periphery. A similar, but less significant change was observe d in the radicle apex, however, the cells in the radicle showed dramatic plasm olysis and vacuolation. In summary, the present study suggested that the more resistant to the desiccation a seed, the more densely of the cytoplasm in the cells of apex of plumule and radicle. Besides, in the desiccation resistant se eds the vacuoles are small or lack, and the predominant storage compounds are oil droplets and protein bodies. The vacuolation of the apical meristematic ce lls and the activity and the quantity of organelles in the cells of embryo axe s are increased with the desiccation susceptibility of the seeds. In the seeds of the five studied species, , highly vacuolation was only found in the plumu le and radicle of Artocarpus seed, and the degree of vacuolation in the other four species is not significantly different, but is highly associated with th eir desiccation susceptibility. VII