The objective of this study is to investigate the physiological mechanisms of plant adaptation under crude oil contamination of soil. Different plant species used in the study sedge (Carex hirta L.), bean (Faba bona Medic.), alfalfa (Medicago lupulina L.) and clover (Trifolium pratense L.) showed various biochemical and morphological reactions under oil pollution. The effect of crude oil on root elongation, shoot growth and dry matter accumulation of the four species was evaluated. All investigated plant species under oil contamination formed powerful root system, however the growth of plant aboveground part was diminished. Results of phytohormones content investigation in C. hirta confirmed that the morphological growth reactions occurred due to changes in phytohormonal balance of plants. Crude oil reduced amount of main growth activator auxin in sedge leaves and stimulated the increase of abscisic acid amount. In sedge roots auxin accumulation occurred under oil contamination. We studied antioxidant system of C. hirta and F. bona plants under oil pollution. Results of our investigations show that for adaptation under oil pollution sedge plants accumulate low molecular weight antioxidants, e.g. polyphenols and maintain reduced cell status due to high reduced/oxidized glutathione ratio in root system. In roots of F.bona activation of antioxidant enzymes catalase and peroxidase under oil effect occured. It was shown that crude oil effects nitrogen metabolism in alfalfa and clover plants. The amount of non-protein and amine nitrogen in plants increased, while the proportion of protein nitrogen decreased under oil contamination. To improve soil nitrogen supply we inoculated the seeds of alfalfa and clover with 348a, BN9 and A91 strains of Rhizobium leguminosarum bv. trifolii for intensification of nodulation in oil contaminated soil. Although the number of nodules on plant roots in oil contaminated soil decreased, their weight was greater than in the control. Improvement of plants nitrogen nutrition in oil contaminated soil requires further investigations.


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