Physiological parameters of young cotton plants, grown on heavy metal contaminated soils
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Author: Lyubka Koleva-Valkova, Andon Vassilev
Metal contamination of the soilis a pressing ecological problem all over the world. A part of the heavy metal contaminated soils in Bulgaria are situated around the Non-ferrous Metals Smelter near Plovdiv (KCMPlovdiv). Implementation of adaptable agriculture (technical crops cultivation) is recommended in this region as a way of reducing human health risk. Cotton is one of the suitable crops for that purpose; therefore the aim of our study was to evaluate the physiological state of young cotton plants, grown on heavy metal contaminated soils from this region. Pot experiments were carried out in climatic rooms at the Department of Plant Physiology and Biochemistry. Young cotton plants (cv. Darmi) were grown on representative soil samples taken around KCMPlovdiv under controlled conditions [(light intensity 250 μmol m-2 s-1 (PPFD), temperature 25°/20°C (day/ night), relative air humidity 60% and photoperiod 16/8 h (light/dark)]. The experimental design included 5 treatments and each treatment was set at 4 replications (3 plants per pot). Four of the treatments represented soils containing Cd, Pb, Zn and Cu in levels exceeding the permissible soil limits, while the fifth contained uncontaminated soil sample (control). Prior to the sowing all pots were fertilized with equal amounts of ½ strength Hoagland nutrient solution. The physiological status of the plants was evaluated three weeks after germination. The analyses included the following parameters: plant biometrics, content of heavy metals in the plant organs, leaf gas exchange, chlorophyll fluorescence, photosynthetic pigments content, etc. The obtained results showed that the physiological state of the cotton plants was differently affected by the metal contaminationof the soil. The most significant variations were reported for the plants grown in the soil ofthe highest metal content.

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