薏苡胚发育及贮藏营养物质积累的研究

薏苡（Ｃｏｉｘ ｌａｃｒｙｍ ａ－ｊｏｂｉ）胚发育分下列各期：棒形胚前的原胚期、棒形胚期、胚芽鞘期、１叶期、２ 叶期、３叶期、４ 叶期、５ 叶期及６叶期成熟胚。３ 叶期胚具１ 条不定根（种子根）,４ 叶期具２ 条,５ 叶期及成熟胚期具３ 条。不定根与胚根排成１ 纵行。营养物质最先在盾片细胞中积累。开花后９ 天的１ 叶期胚,在盾片、胚芽鞘及胚轴细胞中积累了淀粉,以后遍及成熟胚的各部分。淀粉粒含量与器官发生及生长顺序成正相关,但发育后期,盾片细胞内的淀粉粒含量下降。开花后１０ 天,盾片细胞中形成含晶体的蛋白质体,晶体含蛋白质及植酸钙镁。以后,这种蛋白质体增多、增大。同时,又形成不含晶体的蛋白质体。一定时期,含晶体的蛋白质体消失,不含晶体的蛋白质体增多,直到胚成熟。开花后１３ 天,胚芽鞘上部细胞形成蛋白质体。以后遍及成熟胚的各部分,器官发生越早,所含蛋白质体越多、越大。开花后１０ 天,盾片细胞中产生了脂体,成熟胚的盾片细胞,含有大量的脂体。还观察了胚发育各期与颖果及盾片长度的对应关系     

大麦胚和胚乳发育的相关性及贮藏营养物质的积累

大麦(Hordeum vulgare L.)开花后1d,见合子及退化助细胞,游离核胚乳尚未形成;开花后2～3d,胚为5及10个细胞,胚乳为游离核期;开花后4及5、6d,胚为梨形及长梨形,胚乳达细胞化期;开花后8d,胚为胚芽鞘期,糊粉层原始细胞产生;开花后10d,胚具1叶,糊粉层1～2层;开花后13d胚为2叶胚,亚糊粉层发生;开花后17d,3叶胚形成,糊粉层多为3层并停止分裂,菱柱形及不规则胚乳细胞分化;开花后21～29d,胚为4叶胚,胚乳进一步分化;开花后33d,胚为5叶成熟胚,胚乳亦成熟。淀粉、蛋白质在胚中积累始于开花后13d。在盾片中由基向顶发生,在胚芽鞘及叶原基中,首先在顶端出现。成熟盾片顶端的淀粉消失。开花后6d,胚乳开始积累淀粉;开花后10d,糊粉层及胚乳细胞积累蛋白质。开花17d后胚乳的蛋白质体多聚集,29d后蛋白质体显著减少。开花后17d,在盾片及糊粉层细胞中检测到油脂。果长或果长与稃片长之比和盾片长可作为不同发育期胚和胚乳的形态指标。     

The ultrastructure of zygotic embryo development in pearl millet (Pennisetum glaucum; Poaceae)

The ultrastructure, morphology, and histology of zygotic embryogenesis in pearl millet (Pennisetum glaucum) were examined using light and electron microscopic techniques. Embryogenesis was initially characterized by the presence of a vacuolated egg cell and zygote. The increased presence of Golgi bodies in the zygote suggested it was metabolically more active than the egg cell. The first zygotic division resulted in a densely cytoplasmic apical cell and a highly vacuolated basal cell. The club-shaped proembryo displayed a large amount of endoplasmic reticulum (ER) and ribosomes, very few lipids, and a continuous gradient of vacuoles from the highly vacuolated basal suspensor cells to the densely cytoplasmic apical cells. The embryo had well-defined parts by 8 days after pollination, including shoot and root meristems, coleoptile, scutellum, provascular system, and the first leaf primordium. Large increases in ER, lipids, starch, and vacuoles occurred in the scutellum during the maturation of the embryo, except in the provascular cells. Throughout zygotic embryogenesis, embryo cells were connected by plasmodesmata except where intercellular spaces occurred. Ultrastructural, morphological, and histological observations of zygotic embryogenesis in pearl millet are in agreement with previous reports for other grass species.     

Development of Embryo and Endosperm and Nutrient Accumulation in Vigna sesquipedalis (L.) Fruwirth

The structure of embryo sac, fertilization and development of embryo and endosperm in Vigina sesquipedalis (L.) Fruwirth were investigated. Pollization occures 7–10h before anthesis, and fertilization is completed 10 h after anthesis. After fertilization, wall ingrowths are formed at the micropylar and chalazal ends of the embryo sac. Embryo development conforms to the Onagrad type, and passes through 2 or more celled proembryo, long stick-shaped, globular, heart shaped, torpedo, young embryo, growing and enlarging embryo and mature embryo. Wall ingrowths are formed on the walls of basal cells and outer walls of the cells at basal region of suspenser. The suspensor remains as the seed reaches maturity. The starch grains accumulate in the cells of cotyledons by 9–16 days after anthesis, and proteins accumulate by 12–18 days after. The endosperm development follows the nuclear type. The endosperm ceils form at the micropylar end, and remain free nuclear phase at chalazal end. The outer cells are transfer cells. Those cells at the micropylar end form folded cells with wall ingrowths. At heartembryo stage, the endosperm begins to degenerate and disintegrates before the embryo matures.     

Immunodetection and immunolocalization of globulin storage proteins during zygotic and somatic embryo development in Zea mays

Globulins (GLB) are storage proteins that accumulate to high levels during zygotic embryo development of Zea mays L. We visualized the distribution of GLB during zygotic embryo development by immunolabelling of polyethylene glycol sections with a GLB-specific antiserum and a fluorescent secondary antibody. In sections of embryos at 10 days after pollimation (DAP), GLB were detected in the scutellar node only. Sections of embryos of 17 DAP showed, besides the presence of GLB in the scutellar node, the presence of a low amount of GLB in the coleoptile and the leaf primordia. In 30-DAP embryos GLB were localized in the root, the coleorhiza, the leaf primordia, the coleoptile and in all cells of the scutellum with the exception of the epidermis and the pro-vascular tissues. The subcellular location of GLB was visualized by immunolabelling of ultrathin sections with anti-GLB and a gold-conjugated secondary antibody. Scutellum cells and root cortex cells of 30-DAP embryos were packed with protein storage vacuoles (PSV), which differed in electron density. GLB were either evenly distributed throughout the PSV or were localized in electron-dense inclusions within the PSV. SDS-PAGE and immunoblot analysis of total protein extracts indicated the presence of a low amount of the GLB1 processing intermediate proGLB1' in globular as well as mature somatic embryos. After maturation on an ABA-containing medium, somatic embryos showed the additional presence of the next GLB1 processing intermediate GLB1'. By immuno-electron microscopy it was possible to localize GLB in globular deposits in PSV in scutellum cells of these somatic embryos.     

Quantitative analysis of ultrastructural changes during zygotic and somatic embryogenesis in pearl millet (Pennisetum glaucum [L.] R. Br.)

Ultrastructural changes during zygotic and somatic embryogenesis in pearl millet (Pennisetum glaucum [L.] R. Br.) were quantified using morphometric techniques. The total area per cell profile and the cell volume percentage of the whole cell, endoplasmic reticulum (ER), Golgi bodies, mitochondria, nuclei, lipids, plastids, starch grains and vacuoles were measured and comparisons made between three zygotic and three somatic embryo developmental stages. All measurements were taken from scutellar or scutellar-derived cells. Zygotic embryogenesis was characterized by increases in cell size, lipids, plastids, starch, Golgi bodies, mitochondria and ER. Somatic embryogenesis was characterized by two phases of cell development: (1) the dedifferentiation of scutellar cells involving a reduction in cell and vacuole size and an increase in cell activity during somatic proembryoid formation and (2) the development of somatic embryos in which most cell organelle quantities returned to values found in late coleoptile or mature predesiccation zygotic stages. In summary, although their developmental pathways differed, the scutella of somatic embryos displayed cellular variations which were within the ranges observed for later stages of zygotic embryogenesis.     

Immunodetection and immunolocalization of globulin storage proteins during zygotic and somatic embryo development in Zea mays

Globulins (GLB) are storage proteins that accumulate to high levels during zygotic embryo development of Zea mays L. We visualized the distribution of GLB during zygotic embryo development by immunolabelling of polyethylene glycol sections with a GLB-specific antiserum and a fluorescent secondary antibody. In sections of embryos at 10 days after pollimation (DAP), GLB were detected in the scutellar node only. Sections of embryos of 17 DAP showed, besides the presence of GLB in the scutellar node, the presence of a low amount of GLB in the coleoptile and the leaf primordia. In 30-DAP embryos GLB were localized in the root, the coleorhiza, the leaf primordia, the coleoptile and in all cells of the scutellum with the exception of the epidermis and the pro-vascular tissues. The subcellular location of GLB was visualized by immunolabelling of ultrathin sections with anti-GLB and a gold-conjugated secondary antibody. Scutellum cells and root cortex cells of 30-DAP embryos were packed with protein storage vacuoles (PSV), which differed in electron density. GLB were either evenly distributed throughout the PSV or were localized in electron-dense inclusions within the PSV. SDS-PAGE and immunoblot analysis of total protein extracts indicated the presence of a low amount of the GLB1 processing intermediate proGLB1'in globular as well as mature somatic embryos. After maturation on an ABA-containing medium, somatic embryos showed the additional presence of the next GLB1 processing intermediate GLB1. By immuno-electron microscopy it was possible to localize GLB in globular deposits in PSV in scutellum cells of these somatic embryos.     

The ultrastructure of somatic embryo development in pearl millet (Pennisetum glaucum; Poaceae)

The ultrastructure, morphology, and histology of somatic embryogenesis in pearl millet (Pennisetum glaucum) were examined using light and electron microscopic techniques. Somatic embryogenesis was initiated from zygotic embryo explants cultured 8 d after pollination. Formation of a ridge of tissue began 3–4 d after culture (DAC) by divisions in the epidermal and subepidermal cells of the scutellum. Ridge formation was accompanied by a decrease in vacuoles, lipid bodies, and cell size, and an increase in endoplasmic reticulum (ER). Proembryonic cell masses (proembryoids) formed from the scutellar ridge by 10 DAC. Proembryoid cells had abundant Golgi bodies and ER while the amounts of lipids and starch varied. Somatic embryos developed from the proembryonic masses 13 DAC and by 21 DAC had all the parts of mature zygotic embryos. Although shoot and root primordia of somatic embryos were always less differentiated than those of zygotic embryos, scutellar cells of somatic and zygotic embryos had similar amounts of lipids, vacuoles, and starch. Somatic scutellar epidermal cells were more vacuolated than their zygotic counterparts. In contrast, somatic scutellar nodal cells were smaller and not as vacuolated as in zygotic embryos. Somatic embryogenesis was characterized by three phases of cell development: first, scutellar cell dedifferentiation with a reduction in lipids and cell and vacuole size; second, proembryoid formation with high levels of ER; and third, the development of somatic embryos that were functionally and morphologically similar to zygotic embryos.     

Endosperm sterol phenotype and germination in wheat

Free and conjugated sterols of endosperm, coats, scutellum, coleoptile and roots have been analysed at different germination stages in two wheat cultivars with different endosperm sterol phenotypes. It seems that sterol metabolism of the developing tissues, namely coleoptile and roots, is not affected by the sterol conjugation profile of the endosperm. Enough sterol is present in the mature embryo to supply the germinating axis during the observation period (144 hr at 16°). The data suggest that sterol is transferred from scutellum to coleoptile and roots during germination.     

PEARL MILLET (PENNISETUM AMERICANUM (L.) LEEKE) AND GRAIN SORGHUM (SORGHUM BICOLOR (L.) MOENCH) ULTRASTRUCTURE

Ultrastructural features of pearl millet (Pennisetum americanum (L.) Leeke) and grain sorghum (Sorghum bicolor (L.) Moench) caryospses were investigated with thin sections of the dry, mature grain in the transmission electron microscope, and fractured kernels in the scanning electron microscope. The pericarp of those grains is comprised of three distinct layers: epicarp, mesocarp of parenchyma cells, and endocarp of compressed cross and tube cells. Mesocarp cells of grain sorghum contain starch granules embedded in a cytoplasmic matrix. The major constituent of sorghum and millet aleurone cells are aleurone grains (protein bodies) and lipid bodies. Subaleurone cells contain a much higher proportion of protein bodies than starch granules, and the protein bodies are structurally distinct from those in the aleurone. The germ scutellar ultrastructures of the two grains were similar; protein bodies, lipid bodies, epidermal cells and parenchyma cells of the germ are described.     

Fusion of oil bodies in endosperm of oat grains

Few microscopical studies have been made on lipid storage in oat grains, with variable results as to the extent of lipid accumulation in the starchy endosperm. Grains of medium- and high-lipid oat (Avena sativa L.) were studied at two developmental stages and at maturity, by light microscopy using different staining methods, and by scanning and transmission electron microscopy. Discrete oil bodies occurred in the aleurone layer, scutellum and embryo. In contrast, oil bodies in the starchy endosperm often had diffuse boundaries and fused with each other and with protein vacuoles during grain development, forming a continuous oil matrix between the protein and starch components. The different microscopical methods were confirmative to each other regarding the coalescence of oil bodies, a phenomenon probably correlated with the reduced amount of oil-body associated proteins in the endosperm. This was supported experimentally by SDS-PAGE separation of oil-body proteins and immunoblotting and immunolocalization with antibodies against a 16 kD oil-body protein. Much more oil-body proteins per amount of oil occurred in the embryo and scutellum than in the endosperm. Immunolocalization of 14 and 16 kD oil-body associated proteins on sectioned grains resulted in more heavy labeling of the embryo, scutellum and aleurone layer than the rest of the endosperm. Observations on the appearance of oil bodies at an early stage of development pertain to the prevailing hypotheses of oil-body biogenesis.     

Systematic significance of mature embryo of bamboos

The mature embryo of seven species belonging to five genera of Indian bamboos is described. In all these the basic pattern of embryo organisation is same: the scutellar and coleoptilar bundles are not separated by an internode, the epiblast is absent, the lower portion of the scutellum and the coleorhiza are separated by a cleft and the margins of embryonic leaves overlap. The features unique to fleshy fruited bamboos are: presence of a massive scutellum, the juxtaposition of plumule and radicle and the occurrence of a bud in the axil of the coleoptile. The fleshy fruit bearing bamboos should be classified into one group, the tribeMelocanneae. Evidence is provided to recognise additional groups in the subfamilyBambusoideae.     

THE ULTRASTRUCTURAL MORPHOLOGY AND ONTOGENY OF OAT COLEOPTILE PLASTIDS

Structurally similar proplastids occur in the shoot, scutellum, and root of the oat embryo at the start of germination. These proplastids follow several pathways of differentiation, depending on their location within an organ and on previous exposure to light. During the first 24 hr of germination morphologically similar amyloplasts are formed from the preexisting proplastids in most of the cells of the seedling. After about 24 hr in the light, unique chloroplasts begin to develop in a subepidermal ring of small cortical parenchyma cells in the coleoptile and give the organ a pale green color. At 48 and 72 hr the coleoptile chloroplasts and etioplasts are conspicuously different from the corresponding leaf plastids in morphology and ontogeny but contain typical photosynthetic grana and prolamellar bodies. Study of the ontogeny of plastids in the epidermal and nongreening parenchymal regions of dark grown coleoptiles shows that these plastids undergo significant losses in starch content, and some increase of membranes within the plastid, related to the age of the cell. Light has little effect on the structure of these plastids. It is suggested that the ontogeny of all the plastid types of the oat seedling begins with a common precursor—a relatively simple proplastid that is present at the time of germination. Starch grains showing two distinct types of erosion, apparently enzymatic, were observed in oat coleoptile plastids. In one type (grooved appearance) the starch grains are consistently associated with plastid membranes, while in the other type (irregular, spiny appearance) the starch grains are associated with the plastid stroma only. We suggest that there are two enzyme systems for metabolizing starch in oat plastids—one membrane-bound and the other free in the stroma.     

Seed Structure and Localization of Reserves inChenopodium quinoa

The three areas of food reserves in quinoa seeds are: a largecentral perisperm, a peripheral embryo and a one to two-celllayered endosperm surrounding the hypocotyl-radicle axis ofthe embryo. Cytochemical and ultrastructural analysis revealedthat starch grains occupy the cells of the perisperm, whilelipid bodies, protein bodies with globoid crystals of phytin,and proplastids with deposits of phytoferritin are the storagecomponents of the cells of the endosperm and embryo tissues.EDX analysis of the endosperm and embryo protein bodies revealedthat globoid crystals contain phosphorus, potassium and magnesium.These results are compared with studies on other perispermousseeds published to date.Copyright 1998 Annals of Botany Company Chenopodium quinoa,EDX analysis, phytoferritin, phytin, protein bodies, quinoa, seed structure, seed reserves, starch grains.     

Starch deposition and amylase accumulation during somatic embryogenesis in bamboo (Dendrocalamus hamiltonii)

In monocots, the zygotic embryo is protected and nourished by an endosperm. In the present study starch deposition and amylase accumulation was noticed during somatic embryogenesis in stem callus of a bamboo, Dendrocalamus hamiltonii. SEM studies revealed that starch grains were clearly visible in the scutellum during the maturation stage of the somatic embryo. As the somatic embryo developed further, the scutellum got reduced with corresponding increase in amylase. The amylase activity was tested periodically at different developmental stages of embryos. The role of scutellum in somatic embryos for starch deposition and amylase accumulation is discussed.     

Fine structural observations of embryo development inPelargonium XHortorum bailey: with normal and mutant plastids

Summary The ultrastructural changes in the cotyledon, radicle and suspensor haustorium ofPelargonium, containing either normal or mutant plastids, are investigated from the heart stage of embryogenesis to the mature seed. The fine structure of parenchymatous cells from the cotyledon and radicle is essentially similar whereas that of the suspensor haustorium is very different.The cotyledon and radicle develop into one massive storage tissue possessing numerous lipid and several protein bodies per cell, and well developed starch grains. The suspensor haustorium has no storage function, rather it acts as a transitory tissue which dies off as the seed matures. The extensive chloroplast development suggests that, in addition to its traditional role, the suspensor haustorium also acts as a photosynthetic booster for the developing embryo.The development of surviving mutant embryos is similar to normal ones except that in cotyledon and radicle cells plastids develop only to vesicles, which associate into loose prolamellar bodies and sometimes small fenestrated thylakoids, and in the suspensor haustorium cells, only to small compact grana.     

长喙毛茛泽泻胚中营养物质的积累与消耗

长喙毛茛泽泻是一种水生濒危植物。它的种子中没有胚乳,营养物质以淀粉和帽白体的形式贮藏在胚中。胚不同部位物质积累情况差异较大,下胚轴和子地细胞中的淀粉,蛋白体数目多,体积大,胚芽和胚根分生细胞中只贮藏有少量的淀粉粒和蛋白体。     

Expression of the 30 kD cysteine endoprotease B in germinating barley seeds

The expression of a 30 kD cysteine endoprotease (EP-B) was studied by in situ hybridization and immunomicroscopy to clarify its role in germinating barley grains. At the beginning of germination, EP-B mRNA was expressed in the scutellar epithelium and aleurone cells next to the embryo. Later, mRNA levels were highest in the aleurone layer proceeding to the distal end of the grain. During the first day of germination, EP-B protein was strongly localized to the germ aleurone and scutellar epithelium from where the secretion into the starchy endosperm began. Secretion was also observed to proceed along the aleurone layer to the distal end. These results show that EP-B is differentially localized during germination, and both scutellum and aleurone layer are able to synthesize and secrete EP-B protein.