Cold-acclimation effect on cadmium absorption and biosynthesis of polyphenolics, and free proline and photosynthetic pigments in Spirogyra aequinoctialis

Abstract

Herein, a link has been established between cold acclimation and Cd uptake in Spirogyra aequinoctialis. The water samples supplemented with cadmium (0.1, 0.5, and 1.0 mg/L) were used for plant growth at two different temperatures. Cold-acclimated plants accumulated high concentrations (0.40 ± 0.02 μg/dry biomass) of Cd as compared to non-acclimated plants (0.30 ± 0.08 μg/dry biomass). The negative effects of Cd on the biomass, carotenoids, and chlorophyll contents in non-acclimated plants were more pronounced in non-acclimated plants as compared to the cold-acclimated plants. High concentrations of free proline and total phenolics in cold-acclimated plants were observed as compared to the non-acclimated plants. About 13 different phenolic compounds were identified using high-pressure liquid chromatography. Cold acclimation as well as the presence of Cd in water highly increased the concentrations of polyphenolics, while synergistic increase was recorded with the combination of cold acclimation and Cd treatments. The highest increase in the concentration of polyphenolics was recorded for syringic acid. Significant positive correlations of total phenolics were noted with dry biomass (R 2 = 0.51) and Cd accumulation (R 2 = 0.59) in plant tissues. Free proline concentration also showed positive correlations with dry biomass, Cd accumulation, and chlorophyll contents (R 2 = 0.80).