THE SPECTRAL CONTRIBUTION OF CAROTENOIDS TO LIGHT ABSORPTION AND REFLECTANCE IN GREEN LEAVES

Absorbance and reflectance spectra in the visible and near infrared range of the spectrum, acquired for maple (Acer platanoides L.) leaves were studied. Standard deviation of absorbance spectra showed that in yellow to green leaves, with chlorophyll content at least up to 30 nmol/cm2, there is a spectral feature at 520 nm attributable to carotenoids. Reflectance around 520 nm also correlates closely with carotenoids content in yellow to green leaves. Thus, this spectral feature at 520 nm could be used as a measure of carotenoids content in green leaves and plants

Stress-induced changes in the ultrastructure of the photosynthetic apparatus of green microalgae

In photosynthetic organisms including unicellular algae, acclimation to and damage by environmental stresses are readily apparent at the level of the photosynthetic apparatus. Phenotypic manifestations of the stress responses include rapid and dramatic reduction of photosynthetic activity and pigment content aimed at mitigating the risk of photooxidative damage. Although the physiological and molecular mechanisms of these events are well known, the ultrastructural picture of the stress responses is often elusive and frequently controversial. We analyzed an extensive set of transmission electron microscopy images of the microalgal cells obtained across species of Chlorophyta and in a wide range of growth conditions. The results of the analysis allowed us to pinpoint distinct ultrastructural changes typical of normal functioning and emergency reduction of the chloroplast membrane system under high light exposure and/or mineral nutrient starvation. We demonstrate the patterns of the stress-related ultrastructural changes including peculiar thylakoid rearrangements and autophagy-like processes and provide an outlook on their significance for implementation of the stress responses. © 2018, Springer-Verlag GmbH Austria, part of Springer Nature

Stress-induced changes in the ultrastructure of the photosynthetic apparatus of green microalgae

In photosynthetic organisms including unicellular algae, acclimation to and damage by environmental stresses are readily apparent at the level of the photosynthetic apparatus. Phenotypic manifestations of the stress responses include rapid and dramatic reduction of photosynthetic activity and pigment content aimed at mitigating the risk of photooxidative damage. Although the physiological and molecular mechanisms of these events are well known, the ultrastructural picture of the stress responses is often elusive and frequently controversial. We analyzed an extensive set of transmission electron microscopy images of the microalgal cells obtained across species of Chlorophyta and in a wide range of growth conditions. The results of the analysis allowed us to pinpoint distinct ultrastructural changes typical of normal functioning and emergency reduction of the chloroplast membrane system under high light exposure and/or mineral nutrient starvation. We demonstrate the patterns of the stress-related ultrastructural changes including peculiar thylakoid rearrangements and autophagy-like processes and provide an outlook on their significance for implementation of the stress responses. © 2018, Springer-Verlag GmbH Austria, part of Springer Nature

Bio-inspired materials for nutrient biocapture from wastewater: Microalgal cells immobilized on chitosan-based carriers

The successful application of the cross-linked chitosan-based polymers for microalgae immobilization and biocapture of nutrients is reported for the first time. Highly porous, hydrophilic polymers were obtained by cross-linking of 250 kDa or 600 kDa chitosan with glutaraldehyde. Both cross-linked chitosan polymers were characterized by high microalgae immobilization efficiency and supported the prolonged cultivation of immobilized Lobosphaera sp. IPPAS 2047 cells without impairing their growth and photosynthetic activity. The 600 kDA chitosan-based polymers demonstrated higher mechanical and biological stability during 7 d incubation than those based on the 250 kDa chitosan. The nutrient removal capacity of the chitosan-immobilized Lobosphaera cells was significantly higher as compared to that of the suspended cells. The specific removal rates of inorganic phosphate and nitrate by the suspended microalgae cells cultivated without cross-linked chitosan polymers comprised 0.36 and 0.50 mg mg−1 Chl d−1, while the chitosan-immobilized Lobosphaera cells consumed phosphate and nitrate at rates 6.01 and 0.65 mg mg−1 Chl d−1, respectively. Collectively, the cross-linked chitosan-based polymers were shown to be environment-friendly materials providing the enhancement of nutrients bioremoval from wastewater by immobilized microalgae cells. The nutrient-enriched microalgae biomass immobilized on the biodegradable and non-toxic chitosan carriers can be applied as slow-releasing biofertilizer. © 2020 Elsevier Lt