• 作者： 鍾美珠; 吳信淦
• 作者服務機構： 中央研究院植物研究所
• 中文摘要： 在減壓、乾燥、低溫和間歇振動的情況下，依材料的老嫩程度而延長包埋劑滲入組織塊的時間，改良切塊品質，研究稻（Oryza sativa L.）穎果的發育過程。觀察項目包括幼胚、穎果外皮、糊粉層和胚乳等四個部份。 在開花後8小時，卵細胞為一個多夜胞的單細胞，似尚未授精。1～3天幼胚為一個沒有分化的多細胞球體，細胞分裂頻繁。到開花後5天，幼胚在形態上可以區分內、外子葉、胚芽鞘和胚軸等；依據微細構造，幼胚的細胞可分成：(1)表皮細胞，指內、外子葉和胚芽鞘的表皮細胞；(2)細胞分裂旺盛的細胞，此時胚尚未完全分化，多數細胞仍在進行細胞分裂；(3)已經開始分化的細胞。其中(3)所含油滴最多，而(1)中核醣體多，油滴較少，(2)細胞核較大。 穎果外皮由果皮、種皮及珠心構成。果皮由子房壁發育成，種皮由與珠心相鄰的一層內珠被細胞發育成。在穎果發育初期，珠心細胞具有較多的粗面內質網，可能與運送合成胚乳內貯藏性物質的原料有關。種皮與珠心相鄰的細胞壁上有角質層。開花後14天，果皮、種皮等各層細胞開始相互擠壓乾癟，而珠心細胞稍晚才開始。開花後21天，穎果外皮的發育已告終結。 糊粉層是由胚乳細胞發育而來的。糊粉層細胞在開花後4天，出現油滴，7天出現糊粉粒；後者此時只有一個會被甲苯胺藍染成紅色的球體。21天時，糊粉層細胞富含油滴和糊粉粒，糊粉粒除了一個紅色的球體外，其旁有一個染成綠色的球體；前者充滿了可能為植酸鈣鎂的小顆粒，後者則可能含有蛋白、碳水複合物。 成熟穎果，近糊粉層的幾層胚乳細胞中充滿了澱粉粒和蛋白顆粒。這些細胞中在開花後3天出現澱粉粒，由含若干澱粉單粒的澱粉質體發育而成。蛋白顆粒在開花後7天出現，依形態可分成球形和多角形兩種，球形蛋白顆粒為同心圓環層狀結構，而多角形蛋白顆粒由若干小單位構成，形狀不規則。開花後21天，澱粉粒及蛋白顆粒均幾已發育成熟。
• 英文摘要： The development of the caryopsis of rice(Oryza sativa L.) was studied with an im-droved electron microscopy. Mainly, the du-ration for embedding medium infiltration wasappropriately extended according to the hard-ness of the tissue texture under a circum-stance that is dry, low pressure, low temper-ature and occasional vibration of the vialswith tissues in the medium (Table 1). Theresults are summarized in respect to thefollowing four parts of the caryopsis, i.e.,the young embryo, the coat, the aleuronelayer snd the endosperm. The egg remains highly vacuolated (Fig.1,5) at eight hours after flowering; it islikely that the egg is not yet fertilized. Theyoung embryo is not differentiated untill 3days after flowering (DAF), however mostcells are active in division (Fig. 3). At 5DAF, the young embryo is almost completewith scutellum, epiblast, coleoptile and embroyaxis (Fig.4). With respect to ultrastructure,the embryonic cells can identified as: (1)the epidermal cells of scutellum, epiblast andcoleoptile have more ribosomes, (2) the cellsare active in cell division, which have largernucleus (Fig. 8), and (3) the cells which aregoing on differentiation and rich in lipid(Fig. 7). The rice caryopsis coat consists of peri-carp, seed coat and nucellus. The pericarp isderived from the ovary wall which is composedof exocarp, mesocarp, chloroplast layer andendocarp (Fig· 11-14)· The inner integumencell layer adjacent to nucellus is developedinto seed coat (Fig. 9,10 ＆ 16). At earlydeveloping stage, nucellar cells may beinvolved in the translocation of precusors intoendosperm, becsuse the cells are rich in roughendoplasmic reticulum (Fig. 17). Starting from 14 DAF, caryopsis coats are going tobe crushed; the crush of nucellus is obviouslydelayed. At 21 DAF, caryopsis coat is formedwith prominent cuticule layey at both seedcoat and nucellus (Fig. 18). Aleurone layer is differentiated from theoutermost one or two cell layers of endospermAleurone cells begin to have lipids at 4 DAF(Fig. 19) and to have aleurone grains at 7DAF (Fig. 20). At this stage, the youngaleurone grain only has the globoid (Fig. 20)staining red (with toluidine blue, pH＝11.0).At 21 DAF, the aleurone cells are filled withlipid besides the mature aleurone grains eachof which consists of two types of globoids(Fig. 21), staining red and green respectively(stained with toluidine blue, pH＝11). Thered one is with membrane and composed offine granules which is likely of phytin, whilethe green one, which lays beside the former,is without membrane but homogeneous andprobably composed of protein-carbohydratecomplex. It appears that the development ofthe green globoid is later than that of the redone. In endosperm, several cell layers at theinner side of aleurone are rich in both starchgrains and protein bodies. Starch granulessynthesized in plastid appear at 3 DAF, andprotein bodies at 7 DAF (Fig. 26). Proteinbodies are of two types, round and angular.The former is round in shape and with con-centric rings in its cross secticn (Fig. 27),the later is obviously composed of smallangular subunits (Fig. 28). At 21 DAF, bothstarch grains and protein bodies are almost attheir full size (Fig.29).
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