Analyses and localization of pectin-like carbohydrates in cell wall and mucilage of the green alga Netrium digitus

The unicellular, simply shaped desmid Netrium digitus inhabiting acid bog ponds grows in two phases. Prior to division, the cell elongates at its central zone, whereas in a second phase, polar tip growth occurs. Electron microscopy demonstrates that Netrium is surrounded by a morphologically homogeneous cell wall, which lacks pores. Immunocytochemical and biochemical analyses give insight into physical wall properties and, thus, into adaptation to the extreme environment. The monoclonal antibodies JIM5 and JIM7 directed against pectic epitopes with different degrees of esterification label preferentially growing wall zones in Netrium. In contrast, 2F4 marks the cell wall only after experimental de-esterification. Electron energy loss spectroscopy reveals Ca-binding capacities of pectins and gives indirect evidence for the degree of their esterification. An antibody raised against Netrium mucilage is not only specific to mucilage but also recognizes wall components in transmission electron microscopy and dot blots. These results indicate a smooth transition between mucilage and the cell wall in Netrium

Photosynthesis and heat response of the green alga Micrasterias denticulata (Desmidiaceae).

Cells of the green alga Micrasterias denticulata cultivated at 15 degrees C, 20 degrees C or 25 degrees C were exposed to heat shocks at different temperatures (30-40 degrees C) for varying duration (5-90 min). Cell pattern formation, division rate as well as photosynthesis and respiration by measuring oxygen production and consumption have been studied. The degree of cell shape malformations was found dependent on the preceding cultivation temperature along with the mode of the heat shock. Cells cultivated at 15 degrees C and 20 degrees C could counteract a 90 min heat shock at 35 degrees C much better than those cultivated at 25 degrees C, which was seen by a less reduced young semicell. Cells cultivated at 15 degrees C and 25 degrees C reveal a reduced division activity compared to those grown at 20 degrees C even with a marked retardation when affected by a preceding heat shock. Photosynthesis and the level of plastid pigments (carotenoids, chlorophylls, beta-carotene, lutein) of controls determined by HPLC analysis reached a plateau after about 26 days when starting with 22-day old cultures. Photosynthesis and respiration were determined in a range between 15 degrees C and 40 degrees C in defined Micrasterias cell cultures of about this age (cultivation temperature 15 degrees C, 20 degrees C or 25 degrees C). Both processes rose steadily with increasing temperature starting with 15 degrees C and reached peaks between 30 degrees C and 32 degrees C, followed by a considerable drop when increasing the incubation temperature up to 40 degrees C. The experiments reveal that primary processes of energy formation and consumption are much less affected by temperature influences than cell shape formation and division rate

Analyses and localization of pectin-like carbohydrates in cell wall and mucilage of the green alga Netrium digitus

The unicellular, simply shaped desmid Netrium digitus inhabiting acid bog ponds grows in two phases. Prior to division, the cell elongates at its central zone, whereas in a second phase, polar tip growth occurs. Electron microscopy demonstrates that Netrium is surrounded by a morphologically homogeneous cell wall, which lacks pores. Immunocytochemical and biochemical analyses give insight into physical wall properties and, thus, into adaptation to the extreme environment. The monoclonal antibodies JIM5 and JIM7 directed against pectic epitopes with different degrees of esterification label preferentially growing wall zones in Netrium. In contrast, 2F4 marks the cell wall only after experimental de-esterification. Electron energy loss spectroscopy reveals Ca-binding capacities of pectins and gives indirect evidence for the degree of their esterification. An antibody raised against Netrium mucilage is not only specific to mucilage but also recognizes wall components in transmission electron microscopy and dot blots. These results indicate a smooth transition between mucilage and the cell wall in Netrium. © 2009 The Author(s)