Studies on the morphology of the megaecade limícola of Fucus vesiculosus L. with taxonomical comments

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Light quality affects morphology and polysaccharide yield and composition of Gelidium sesquipedale (Rhodophyceae)

International audienceMorphology and polysaccharide characterization of Gelidium sesquipedale (Clem.) Bornet et Thuret were studied in cultures grown under various light qualities. White light (WL), blue light (BL) and red light (RL) (all at photon fluence rate of 40 μmol m-2 s-1) were used for the study of morphological characteristics, and in addition yellow light (YL) for polysaccharide characterization. RL and BL induced a proliferating growth, which resulted in bushy plants under RL. Cortical cells of BL-grown plants were smaller and presented a higher density per unit area, whereas those of WL- and RL-grown alga were larger. Medullary cells followed the inverse pattern. Light quality also affected polysaccharide yield and composition, with the yield being higher under BL, RL or YL than WL. Most of the polysaccharide was extracted in distilled water at 100 °C, while a low amount was solubilized at 22 °C and 120 °C. Extracts from BL-grown alga presented the highest galactan content. The starch concentration was lower in extracts from RL-, BL- and YL-cultivated alga than in those from the initial plants. The degree of substitution with methoxyl groups and precursor was very low in all the agar fractions, but fractions extracted from BL- and WL-grown alga were more substituted by precursor. The highest sulfate content was reached under BL (about 9% w/w) and the highest 2-O-methyl-3,6-anhydro-L-galactose and 6-O-methyl-D-galactose content were found in extracts from alga grown under YL

Light-dependent uptake, translocation and foliar release of phosphorus by the intertidal seagrass Zostera noltii Hornem

Light-dependent P uptake by root-rhizomes, acropetal translocation and subsequent foliar release by Zostera noltii Hornem. was studied under laboratory conditions in two-compartment chambers using 32P. The uptake by underground parts was unaffected by light conditions but the acropetal translocation proceeded more rapidly in light than in dark, indicating a coupling to the metabolic activity of the plants. The translocated P was mainly accumulated in the youngest leaves (30%), i.e., the most actively growing parts. Foliar release of P might be considered negligible (2–4% of the P taken up by root-rhizomes), indicating that the role of Z. noltii as a “P pump” is of minor importance in the cycling of P between sediment and water. This was calculated for part of the Oosterschelde estuary, Zeeland, The Netherlands

Diversity of inorganic carbon acquisition mechanisms by intact microbial mats of Microcholeus chtonoplantes Thuret (Cyanobacteriae, Oscillatoriaceae)

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