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Ultrastructure of develqping chloroplasts and chlorophyll content in a hornwort sporophyte as affected by darkness
No full textCHLOROPLAST DEVELOPMENT IN LIGHT‐ AND DARK‐GROWN SPOROPHYTES OF PHAEOCEROS LAEVIS (L.) PROSK. (ANTHOCEROTOPHYTA)
No full textChloroplast development in light and in darkness was investigated in the sporophyte of the anthocerote, Phaeoceros laevis (L.) Prosk. In both light‐and dark‐grown sporophytes, chloroplasts with an elaborate inner membrane system were found in chlorenchyma cells about 3 mm from the sporophyte base. Development in the dark resulted in a net increase of the average number of grana per unit of chloroplast area and of thylakoids per granum, and a parallel diminution in the chlorophyll a/b ratio. Substantial amounts of chlorophyll were synthesized in the dark. Small, paracrystalline arrays of membranes associated with extensive thylakoid stacks were found in immature plastids of dark‐grown sporophytes. These structures disappeared during early stages of subsequent chloroplast differentiation. These results are the first indication that the anthocerotes do not require light for the differentiation of their photosynthetic apparatus. Copyright © 1987, Wiley Blackwell. All rights reserve
Aspetti fisiomorfologici della resistenza all'aridità in alcune specie del genere Sansevieria
No full textUltrastuctural changes and levels of CAM activity on recovery from water stress in Cissus quadrangularis L.
No full textA cytochemical and immunocytochemical analysis of the wall labyrinth apparatus in leaf transfer cells in Elodea canadensis
No full text† Background and Aims Transfer cells are plant cells specialized in apoplast/symplast transport and characterized
by a distinctive wall labyrinth apparatus. The molecular architecture and biochemistry of the labyrinth apparatus
are poorly known. The leaf lamina in the aquatic angiosperm Elodea canadensis consists of only two cell layers,
with the abaxial cells developing as transfer cells. The present study investigated biochemical properties of wall
ingrowths and associated plasmalemma in these cells.
† Methods Leaves of Elodea were examined by light and electron microscopy and ATPase activity was localized
cytochemically. Immunogold electron microscopy was employed to localize carbohydrate epitopes associated
with major cell wall polysaccharides and glycoproteins.
† Key Results The plasmalemma associated with the wall labyrinth is strongly enriched in light-dependent
ATPase activity. The wall ingrowths and an underlying wall layer share an LM11 epitope probably associated
with glucuronoarabinoxylan and a CCRC-M7 epitope typically associated with rhamnogalacturonan I. No labelling
was observed with LM10, an antibody that recognizes low-substituted and unsubstituted xylan, a polysaccharide
consistently associated with secondary cell walls. The JIM5 and JIM7 epitopes, associated with
homogalacturonan with different degrees of methylation, appear to be absent in the wall labyrinth but present
in the rest of cell walls.
†Conclusions The wall labyrinth apparatus of leaf transfer cells in Elodea is a specialized structure with distinctive
biochemical properties. The high level of light-dependent ATPase activity in the plasmalemma lining the
wall labyrinth is consistent with a formerly suggested role of leaf transfer cells in enhancing inorganic carbon
inflow. The wall labyrinth is a part of the primary cell wall. The discovery that the wall ingrowths in Elodea
have an antibody-binding pattern divergent, in part, from that of the rest of cell wall suggests that their carbohydrate
composition is modulated in relation to transfer cell functioning
Histochemistry, ultrastructure and possible significance of dead parenchyma cells with specialized walls in the leaf and rhizome of Sansevieria
No full textAbstract. The internal parenchyma of the leaf and rhizome in 36 species of Sansevieria is made of dead cells and living cells arranged in a regular pattern. Intercellular spaces are lacking. The walls of dead cells consist of an inner amorphous layer positive to the fluorescence test for callose, a middle suberin‐like layer and an outer fibrillar layer. In about half of the species examined, the inner layer forms distinctive thickenings. Detached leaves of Sansevieria lose water very slowly, and are able to recover it quickly. The pattern of leaf dehydration appears to be related to leaf morphology, whereas no relation is evident between the pattern of leaf rehydration and leaf morphology. Neither leaf dehydration nor leaf rehydration pattern is affected by the presence of wall thickenings in the dead parenchyma cells. The fresh weight per unit volume of both turgid and droughted leaves is nearly 1, denoting that the dead cells are filled with water and do not undergo substantial cavitation during drought. The data indicate that the dead parenchyma cells of Sansevieria are a specialized water‐storing system. Copyright © 1989, Wiley Blackwell. All rights reserve
Effects of the potential allelochemical a-asarone on growth, physiology and ultrastructure of two unicellular green algae.
No full textLinolenic acid as a potential allelochemical released by Eichhornia crassipes (Mart.) Solms in a continuous trapping apparatus.
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