Charophyte Algae Research Articles

Osmotic adaptations of charophyte algae in the Coorong, South Australia and other Australian lakes

Lamprothamnium is found in salinities varying from nearly fresh to twice sea water in coastal saline lakes in South Australia, Victoria, and New South Wales. It maintains its turgor (ΔP≅ΔII) approximately constant over this range, varying internal osmotic pressure by altering KCl concentration (although at the highest salinity, Na+ concentration became more important). The ability to regulate turgor with alterations in salinity is wide-spread in marine algae, but has not been reported for the freshwater charophytes. Lamprothamnium is also unusual among algae and particularly among charophytes in having a high concentration of sucrose (up to 300 mM) in the vacuole. Vacuolar concentration is not correlated with salinity and its adaptive significance is not known, although in the cytoplasm sucrose may play a significant role in osmotic adaptation.

C4 characteristics of photosynthesis in the C3 alga Hydrodictyon africanum

Abstract Results obtained with Hydrodictyon africanum, and data from the literature, show that most green algae of the chlorophyte type (e.g. Chlorella, Chlamydomonas, Hydrodictyon) differ in their photosynthetic C fixation characteristics from most green algae of the charophyte type (e.g. Spirogyra, Chara) and from C3 higher plants. The chlorophyte algae fix inorganic carbon by the photosynthetic carbon reduction cycle pathway, but have a low CO2 compensation point in 250 μM O2, a low inhibition of CO2 fixation from 10 μM CO2/250 μM O2 when compared with 10 μM CO2/zero O2, and a low half‐saturation constant for CO2. These three characteristics are different from those of charophytes and C3 higher plants, and resemble those of C4 higher plants. It is suggested that these characteristics of chlorophyte algae are the result of a ‘CO2 concentrating mechanism’ which increases the CO2/O2 ratio at the site of ribulose bisphosphate carboxylase‐oxygenase action in a similar way to that achieved by the C4?C3 acid cycle in C4 plants. In the chlorophyte algae, however, CO2 concentration probably involves active HCO3− transport at the inner membrane of the chloroplast envelope. Active HCO3− transport can occur at the plasmalemma of charophyte algae and submerged aquatic higher plants as well as chlorophyte algae, so it is unlikely to explain the differences between the two groups of aquatic green plants. Differences in the properties of ribulose bisphosphate carboxylase‐oxygenase, and differences in CO2 production in the light, also seem inadequate to account for the different photosynthetic characteristics. The chlorophyte type of ‘C02 concentrating mechanism’ appears to be common in other classes of eukaryotic algae, and in cyanophytes. Some of the ‘advanced’ members of these eukaryotic algal classes (including the chlorophytes) may lack the mechanism, while some ‘primitive’ charophytes may retain the mechanism which their ancestors presumably possessed.

A scanning electron microscope study of the structure and organization of the calcium carbonate deposits of algae

Abstract The calcium carbonate deposits of Cyanophyte, Charophyte, Chlorophyte, Phaeophyte and Rhodophyte algae have been studied with the scanning electron microscope. The SEM permitted in situ observation of these deposits, which allowed the crystal structure and the organization of the crystalline deposits to be observed. The CaCO3 was deposited either as argonite or calcite. The CaCO3 depositing algae can be grouped into three major groups according to the organization and site of deposition of the crystals. The first group (Group A) exhibits extreme organization and the CaCO3 is deposited on an organic matrix within the cell. The deposits of algae of Group B are formed within the cell wall or mucilage and also show some organization. The deposits of algae of Group C are completely extracellular and exhibit no organization.

Carbonate deposition on the river floodplains of the Wood Bay Formation (Devonian) of Spitsbergen

SummaryThe argillaceous siltstones of the floodplains contain, on average, 15% of calcium carbonate. This appears to have been precipitated between the detrital grains shortly after their deposition. The siltstones also contain calcium carbonate concretions which formed as the ground water dried out in the upper part of the water table. Bedded marlstones, containing up to 68% of carbonate in the lakes appears to have been stimulated by Charophyte algae. The marlstones include dolomite in some parts of the Formation. The channel-fill deposits include carbonate detritus from the source areas, and from reworking of Wood Bay Formation sediments. They are frequently cemented by calcite.The regional pattern of carbonate derivation, transportation and deposition is summarized.

Über die Zygotenbildung bei Micrasterias papillifera Bréb.

Land plants evolved from charophytic algae, among which Charophyceae possess the most complex body plans. We present the genome of Chara braunii; comparison of the genome to those of land plants identified evolutionary novelties for plant terrestrialization and land plant heritage genes. C. braunii employs unique xylan synthases for cell wall biosynthesis, a phragmoplast (cell separation) mechanism similar to that of land plants, and many phytohormones. C. braunii plastids are controlled via land-plant-like retrograde signaling, and transcriptional regulation is more elaborate than in other algae. The morphological complexity of this organism may result from expanded gene families, with three cases of particular note: genes effecting tolerance to reactive oxygen species (ROS), LysM receptor-like kinases, and transcription factors (TFs). Transcriptomic analysis of sexual reproductive structures reveals intricate control by TFs, activity of the ROS gene network, and the ancestral use of plant-like storage and stress protection proteins in the zygote.