Chlorophyll and carotenoids: pigments of photosynthetic biomembranes. Meth Enzymol

Methods in enzymology (Impact Factor: 2.09). 01/1987; 148C:350-382. DOI: 10.1016/0076-6879(87)48036-1
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    • "2.2. Methods Total chlorophylls (Chl aþb) and carotenoid contents (Car xþc) were estimated spectrophotometrically (UV/VIS 550, Unicam, UK) from pigment extracts in 80% acetone (Lichtenthaler, 1987 "
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    ABSTRACT: We examined the acclimation response of the photosynthetic apparatus of barley (Hordeum vulgare L.) to a combination of UV-A and UV-B radiation (UVAB) and to UV-B radiation alone. Our aim was to evaluate whether UV-A radiation prevents UV-B-induced damage to the photosynthetic apparatus and whether UV-A pre-acclimation is required to mitigate the negative influence of UV-B radiation. Barley plants were grown from seeds under low photosynthetically active radiation (50 μmol m(-2) s(-1)) either in the absence or presence of UV-A radiation (UVA- and UVA+ plants, respectively). After 8 days of development, plants were exposed simultaneously to UV-A and UV-B radiation for the next 6 days. Additionally, UVA- plants were exposed to UV-B radiation alone. The UVA+ plants had a higher CO2 assimilation rate near the light-saturation region (AN) and a higher content of both total chlorophylls (Chls) and total carotenoids than the UVA- plants. Chls content, AN, the potential quantum yield of photosystem II (PSII) photochemistry (FV/FM), the capacity of light-induced thermal energy dissipation and the efficiency of excitation energy transfer within PSII remained the same or even increased in both UVA+ and UVA- plants after UVAB treatment. On the contrary, exposure of UVA- plants to UV-B radiation itself led to a reduction in all these characteristics. We revealed that the presence of UV-A radiation during UVAB treatment not only mitigated but completely eliminated the negative effect of UV-B radiation on the functioning of the photosynthetic apparatus and that UV-A pre-acclimation was not crucial for development of this UV-A-induced resistance against UV-B irradiation. Copyright © 2015 Elsevier Masson SAS. All rights reserved.
    Plant Physiology and Biochemistry 11/2015; 96:90-96. DOI:10.1016/j.plaphy.2015.07.017 · 2.76 Impact Factor
    • "Initial chlorophyll content was 12 ± 2 mg/l. Chlorophyll concentration was determined spectrophotometrically according to Lichtenthaler [15]. The F v /F m (variableto-maximum fluorescence) which indicates the maximum quantum yield of Photosystem II, was measured in dark adapted cells (15 min) using a portable pulse-amplitudemodulation fluorometer, PAM-2100 (H. "
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    ABSTRACT: Biological hydrogen production is being evaluated for use as fuel, since it is a promising substitute for carbonaceous fuels owing to its high conversion efficiency and high specific energy content. The microalga Chlamydomonas reinhardtii when grown under sulfur-deprived conditions, switches the metabolism toward the production of hydrogen. A better understandings of physiological and biochemical changes occurring during each phases of the process, represents a prerequisite to enhance the hydrogen output. The aim of this work was to study whether the activation of enzymes of the antioxidant defense system, such as catalase (CAT), ascorbate peroxidase (APOX) and guaiacol peroxidase (GPOX), takes place during the entire process of hydrogen production by C. reinhardtii CC 124. Kinase activities present in the crude protein extract and the mitotic specific ones associated with CKS1 protein were assayed to determine how the conditions leading to hydrogen production affected the activities of mitotic and growth associated kinases. We present evidences that oxidative stress enzymes are active during the entire hydrogen production process, besides their activities are higher in the anoxic phase. Stress condition during hydrogen photoproduction provoked at least partial cell cycle arrest leading to block of mitosis and cell division. These findings are in line with the known down-regulation or block of cell cycle related processes in stressed or starved cells.
    International Journal of Hydrogen Energy 09/2015; 40(33):10410. DOI:10.1016/j.ijhydene.2015.06.124 · 3.31 Impact Factor
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    • "Photosynthetic pigments were extracted in ice cold acetone (80%) and read out at 663 and 645 nm wavelength in a UV-spectrophotometer (UV-4000, ORI, Germany). These are expressed as mg g −1 fresh leaf weight (Lichtenthaler, 1987). Determinations were made as per treatment and replication. "
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    ABSTRACT: Phytotoxic effects of parthenium residues incorporation and parthenium-infested rhizospheric soil on emergence and seedling growth of winter crops (wheat and canola) and weed species (wild oat and canary grass) were examined in different pot studies. In first experiment, parthenium whole plant residues were incorporated at 6 and 8gkg(-1) soil five days prior to sowing. Pots without residues incorporation were maintained as control. In a second study, parthenium-infested rhizospheric soil collected from different depths (15 and 22.5cm) and collar regions (horizontal distance away from plant trunk, 15 and 22.5cm), was used as growing medium. Parthenium-free soil was used as control. Parthenium residues amendment as well as its rhizospheric soil was detrimental for emergence and seedling growth of all test species. Incorporation of parthenium residues reduced the final emergence of canola, wild oat and canary grass by 11-20%, 20-29% and 20-27%, respectively; however wheat emergence was unaffected. Moreover, seedling biomass of wheat, canola, wild oat and canary grass was reduced in the range of 41-48%, 53-61%, 31-45% and 30-45% by parthenium residues incorporation. In second study, soil collected from a rhizospheric depth of 15cm and collar distance of 15cm reduced the emergence and seedling growth by 15% and 40%, respectively averaged across different test species. Parthenium residues incorporation and infested rhizospheric soil increased the soil phenolics, electrical conductivity, organic carbon and nitrogen contents over control soils with the exception of pH that was declined. All test species manifested reduced chlorophyll and increased phenolic contents in response to parthenium residues incorporation and infested rhizospheric soil. The inhibition in emergence and seedling growth of all test species was associated with increase in phenolic contents. Parthenium residues incorporation at 8gkg(-1) soil and upper parthenium-infested rhizospheric soil (15cm soil depth and 15cm collar distance) were more phytotoxic for all test species. Copyright © 2015 Elsevier Inc. All rights reserved.
    Ecotoxicology and Environmental Safety 08/2015; 122. DOI:10.1016/j.ecoenv.2015.08.019 · 2.76 Impact Factor
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