核桃种子油体发育及不同品种种子子叶油体特征差异分析

Oil Body Observation in Seed Development and Its Analysis in Seed of Juglans regia ‘Wen185' and J. regia ‘Xinxin2' in Period of Seed Maturity

【目的】通过观察不同核桃品种种子油体发育过程,分析其成熟期子叶油体特征,旨在寻找核桃种子油体合成的起始时间及发生位置,了解不同品种种子在子叶油体特征上的差异及其与含油率间的关系,加深对新疆早实核桃品种种子细胞超微结构的认识。【方法】以新疆早实核桃品种‘温185’和‘新新2号’为试验材料,采用索式脂肪测定仪检测核桃种子脂肪含量,并运用透射电子显微镜技术观察种子发育进程中细胞器的发育消解及油体发育过程。【结果】花后30 d,核桃种子胚中开始存在单独的细胞,各细胞壁之间界限清晰;单独细胞中开始形成各种细胞器。花后50 d,细胞内的细胞器更为丰富,同时内质网数量不断增多,且以条状为主。花后60d,内质网两端开始膨胀增厚,零星出现油体,随后种子胚中的油体数量不断增加直至成熟。细胞中的内质网数量于花后90 d开始减少,其余各种细胞器于花后110 d开始消解。花后120 d,细胞被油体和蛋白体填满。子叶细胞中的油体积累滞后于胚中的油体积累,花后60 d才开始形成单独细胞且细胞内已出现各种细胞器,同时子叶细胞中的内质网已开始膨胀增厚。至花后80 d,内质网才开始分泌小泡,形成油体,晚于胚20 d。成熟期核桃种子子叶细胞完全被油体和少量蛋白体充实,油体呈椭球体或不规则多面体,较少为球体,且油体个体间的形态与大小特征存在较大差异。种子含油率相对较高的‘温185’子叶贮藏细胞内油体数量较种子含油率相对较低的‘新新2号’少,但其直径和截面积之和却较大,且在两个品种间分别存在极显著(P<0.01)和显著(P<0.05)差异。【结论】核桃种子胚和子叶中的油体主要发生于内质网,在花后60 d开始积累,且子叶中油体的积累滞后于胚,二者不具有同步性。成熟后种子子叶贮藏细胞内油体直径大小和截面积之和是导致‘温185’与‘新新2号’种仁含油率产生差异的内在主要因素。

【Objective】Through the observations of different varieties of walnut seed oil body development processes and the analyses of the mature cotyledon oil body characteristics, we aimed at finding walnut seed oil body synthesis initiation time and location, understanding the relationship between the oil rate and the differences in the cotyledon oil of the seeds of different varieties and deepen the understanding of Xinjiang early fruit walnut seed cell ultrastructure.【Method】The oil content were tested by a fat analyzer. The ultrathin sections of resin embedded seeds were observed by a Transmission Electron Microscope（TEM）. 【Result】Juglans regia ‘Wen185＇ and J. regia ‘Xinxin2＇seeds were used as materials. The results showed that, in the embryo, the cell can be distinguished from each other and organelles such as vacuole, nucleolus, chloroplast, starch grain, endoplasmic reticulum, and mitochondrion, the Golgi＇s body appeared in each cell after 30 days after flowering（DAF）. The number of endoplasmic reticulum were increased after 50 DAF. The tip of the double membrane of endoplasmic reticulum began to be inflated and oil bodies were observed after 60 DAF. The number of oil bodies increased gradually until the fruit matured. The number of endoplasmic reticulum decreased after 90 DAF and organelles disappeared after 110 DAF. The period of organelles which were observed in the cotyledon was later than the embryo. In the period of seed maturity, cells consisted of oil bodies and protein bodies in the cotyledon. The sizes and shapes of the oil bodies were different. Most of oil bodies showed an elliptical or irregular shape. The J. regia ‘Wen185＇ had more oil content than J. regia ‘Xinxin2＇. Also, it was found that the mean size of the oil bodies of the cotyledons for J. regia ‘Wen185＇ was significantly different from the oil bodies of the cotyledons for J. regia ‘Xinxin2＇. J. regia ‘Wen185＇ has less number of oil bodies per cell than J. regia ‘Xinxin2＇. J. regia ‘Wen185＇ has larger oil bodies than J. regia ‘Xinxin2＇. 【Conclusion】These results provide that oil bodies were originated from the endoplasmic reticulum. The period of organelles which were observed in the cotyledon was later than in the embryo. The length and total sum of the areas of the oil bodies correlate well with the oil content of walnut of Juglans regia ‘Wen185＇ and J. regia ‘Xinxin2＇.