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  • 1
    ISSN: 1615-6102
    Keywords: Bean ; Elongation growth ; Osmiophilic particles ; Pea ; Spruce ; Sunflower
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The occurrence of elongation growth-related osmiophilic particles (OPs) was investigated in hypocotyls of sunflower, bean, and spruce as well as in pea epicotyls and in cress roots of intact seedlings. In all analyzed species, OPs were found to occur specifically within the periplasmic space between plasma membrane and the outer epidermal cell walls of elongating parts of hypocotyls, epicotyls, and roots, whereas cells of nonelongating parts were devoid of OPs. Auxin (IAA) markedly increased the number of OPs in epicotyl and hypocotyl segments. Treatment of pea epicotyl segments with the lectin concanavalin A inhibited their elongation growth in the presence of IAA. At a subcellular level this effect was characterized by the occurrence of a pronounced osmiophilic layer in the periplasmic space of the outer periclinal and the outer part of the anticlinal epidermal cell walls. Treatment of IAA-incubated segments with the secretion inhibitor brefeldin A inhibited both elongation growth and periplasmic occurrence of OPs. This effect was accompanied by complementary accumulation of OPs in the peripheral cytoplasm of epidermal cells. Together the results indicate that IAA-induced epidermis-specific secretion of OPs is closely related to cell elongation growth not only in organs of monocotyledonous species, but also in dicotyledonous angiosperms as well as in gymnosperms.
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  • 2
    ISSN: 1615-6102
    Keywords: Arabinogalactan proteins ; Maize ; Phloem ; Root
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cell-specific expression of two arabinogalactan protein (AGP) epitopes recognized by monoclonal antibodies JIM8 and JIM13 is reported in maize roots. Employing immunofluorescence and immunogold electron microscopy, the JIM8 antibody was shown to label exclusively protophloem sieve elements, while the JIM13 antibody labelled sieve elements very strongly and adjacent pericycle and companion cells, as well as sloughing root cap cells less strongly. Since the labelling of sieve elements with JIM8 antibody was specific and did not spread to other cell types during root development, it is concluded that this AGP epitope can serve as a specific marker of these specialized cells within the maize root. In the case of the AGP epitope recognized by JIM13 antibody, part of the immunofluorescence label was also found to be associated with cytoplasmic strands in the pericycle and sloughing root cap cells. Immunogold-labelling of sieve elements revealed the association of both AGP epitopes (JIM8 and JIM13) with cortical sieve element reticulum and plasma membranes. Labelling of sieve element reticulum was prominent at its domains of adhesion to the plasma membrane, P-type plastids, and mitochondria. Based on our subcellular studies, we propose a new function of AGP epitopes in endomembrane recognition and adhesion within the sieve elements of maize roots.
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  • 3
    ISSN: 1615-6102
    Keywords: Actin ; Cadherin ; Catenin ; Endoplasmic-reticulum membrane ; Maize ; Root
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary With heterologous antibodies raised against animal N-cadherin, α-catenin, and β-catenin, we have visualized their reactive proteins within cells of maize root apices. Embedding using Steedman's wax allowed us to accomplish tissue-specific analysis which revealed that cells of epidermis, endodermis/pericycle, and outer stele tissues, all of which are tightly associated to each other, are especially enriched with presumed plant homologues of N-cadherin and both catenins. In the root epidermis, trichoblasts initiating root hairs showed prominent accumulations of cadherin-like antigens at outgrowing domains where they co-localize with actin. Close associations of cadherin-like proteins with F-actin were detected in parenchymatic cells of the stele, also at the immunogold electron microscopy level. A possible role of these interesting proteins in membrane-membrane interactions is indicated by their prominent accumulations at endoplasmic-reticulum-enriched pit-field-based plant cell adhesion domains in plasmolyzing cells of maize root apices exposed to mannitol. Intriguingly, these unique adhesion domains of plasmolyzing cells are enriched with endoplasmic-reticulum-resident calreticulin. Cadherin-like, but not catenin-like, proteins were abundant also within the nucleoplasm.
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  • 4
    ISSN: 1615-6102
    Keywords: Drosera rotundifolia ; Embryogenic callus ; Extracellular matrix ; Scanning electron microscopy ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Primary embryogenic callus ofDrosera rotundifolia and long-term cultured embryogenic callus ofZea mays possess a conspicuous extracellular matrix (ECM) around and between embryogenic cells. The structural arrangement of ECM depends on the developmental stage of the embryogenic cells. Single embryoid cells were covered with, and connected by net-like material. However, surface cells of young globular embryoids were covered with a coherent layer of ECM which forms bridges with net-like material between the cells which was gradually reduced to coarse strands. When protodermis was formed on the surface of globular embryoids, the ECM disappeared completely. The ECM network was never observed on the surface of heart- and torpedo-shaped embryoids. Safranine (especially 0.1%) stabilized the structure of ECM. Digestion with pronase E and proteinase K indicated that the ECM contains proteinaceous components. Similar developmental patterns of ECM were observed in dicotyledonous and monocotyledonous examples. The ECM represents a stable morphological structure even during long-term embryogenic culture in maize.
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  • 5
    ISSN: 1615-6102
    Keywords: Arabinogalactan protein ; Drosera capensis ; Endoplasmic reticulum ; Golgi apparatus ; Tonoplast ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Arabinogalactan proteins (AGPs) are proteoglycans detected in high amounts at plant cell surfaces; however, details of their subcellular localization are largely unknown. Immunolocalization studies with the anti-AGP monoclonal antibody LM2 have indicated that this AGP epitope is associated with secretory compartments such as endoplasmic reticulum and Golgi apparatus within plant cells actively producing and secreting AGPs. The LM2 epitope contains a β-linked glucuronic acid residue and occurs in the polysaccharide moiety of AGPs. We have localized this AGP epitope also to the tonoplast and to cytoplasmic strands. Endomembrane association of AGPs was confirmed with two other monoclonal antibodies, JIM13 and MAC207, both reacting with carbohydrate AGP epitopes containing GlcpA-β(1→3)-D-GalpA-α(1→2)-L-Rha residues. Immunocytochemistry is supported by biochemical analysis which shows that LM2 reacts with the microsomal fraction and also with low-molecular-weight material of the detergent phase after Triton X-114 phase separation prepared from maize roots. Our results indicate that some AGP epitopes are closely associated with endomembranes.
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  • 6
    ISSN: 1573-8264
    Keywords: histology ; scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gemma morphology, histology and ultrastructure before and after germination in vitro were studied in Drosera pygmaea. The histology of the gemma is similar to that of a seed, being characterized by an embryo-like structure and storage tissue, although no seed coat is formed. One embryo-like structure within the gemma, which gives origin to a new plant, expresses polar organisation with distinct meristematic regions. Storage tissue surrounding the embryo-like structure resembles endosperm and it is built of parenchyma cells possessing plastids with starch grains and dense material within vacuoles. The regeneration from the gemma may provide useful system to study plant morphogenesis under stress conditions including in vitro culture.
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  • 7
    ISSN: 1573-8264
    Keywords: kiwifruit ; mesophyll ; stomata ; trichomes ; vascular system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Differences in anatomy and morphology of the kiwifruit leaves and leaf petioles might play a considerable role in the sex-determination. Three months after bud break (June), the kiwifruit leaves of both male and female plants, grown on the vegetative and generative shoots showed different leaf area (128.6 ± 13.45 cm2 in male and 104.5 ± 4.02 cm2 in female plants) and shape. The most frequently leaf shape was determined as "folium cordatum" and "folium rotundato-cordatum". Higher values of total leaf thickness of the female leaves (190 ± 3.84 µm) in comparison to male leaves (174 ± 3.52 µm) were estimated, resulting in the thicker adaxial leaf epidermis and especially in thicker palisade parenchyma in female leaves (136 ± 2.76 µm in comparison to 104 ± 1.61 µm in male leaves). Typically bifacial leaves were observed in both male and female leaves. Anomocytic stomata in hypostomatic leaves were found. The reticulate venation appears to be the main type of leaf venation. Stalked stellate multicellular trichomes on the abaxial leaf side were frequently observed in the leaves of both sexes. No important differences between male and female plants were found in the structures of vascular system in leaves and leaf petioles. Thus leaf thickness and surface morphology of adaxial leaf epidermis can be considered as important structural parameters in the sex determination.
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  • 8
    ISSN: 1573-8264
    Keywords: meristemoids ; nucleus ; shoot regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The first step during shoot primordia development in Papaver somniferum L. was the differentiation of globular meristemoids, resulting from localized cell division in callus tissue. During meristemoid maturation differences observed were in mitotic activity, cytoplasmic density, starch distribution, and in cell size, cell shape, and nucleus size to cell size ratio between peripheral and central meristemoid cells. Cell specialization within the meristemoids is a prerequisite for shoot primordia development.
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  • 9
    ISSN: 1432-203X
    Keywords: Key words Arabinogalactan-proteins ; Somatic embryogenesis ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Embryogenic units of friable maize callus are formed as globular or oblong packets of tightly associated meristematic cells. These units are surrounded by conspicuous cell walls visible in light microscopy after staining with basic fuchsin. Transmission electron microscopy revealed that embryogenic cells are rich in endoplasmic reticulum, polysomes and small protein bodies, and that the outermost layer of their cell walls is composed of fibrillar material. Electron microscopy has also shown that this material covers the surface of embryogenic cells as a distinct layer which we denote as extracellular matrix surface network (ECMSN). Employing histochemical staining with β-glucosyl Yariv phenylglycoside, we localized arabinogalactan-proteins (AGPs) to the outer cell walls of embryogenic units including ECMSN. The most prominent staining was found in cell-cell junction domains. Large non-embryogenic callus cells were not stained with this AGP-specific dye. Immunofluorescence and silver-enhanced immunogold labelling using monoclonal antibody JIM4 has shown that the ECMSN of embryogenic cells is equipped with JIM4 epitope, while non-embryogenic callus cells are devoid of this epitope. We propose that some specific AGPs of the ECMSN might be relevant for cell-cell adhesion and recognition of embryogenic cells during early embryogenic stages, and that the JIM4 antibody can serve as an early marker of embryogenic competence in maize callus culture.
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