Effect of heavy metals on changes in the biochemical profile of pea root exudates

Abstract

By HPLC analysis, a comparative assessment of changes in the qualitative and quantitative indicators of the biochemical composition of low molecular weight root exometabolites in three different genotypes of peas (SGE, SGECDt and Sofya) at an early stage of vegetation under the influence of introducing into the environment toxic concentrations of heavy metals in the form of chlorides (cadmium and/or cobalt - 4 µM / 40 µM). Contamination of the nutrient substrate with salts of heavy metals caused an increase in the total yield of sugars and amino acids in the SGE and SGECDt genotypes. In the variety Sofya, this effect was manifested only in relation to sugars. No statistically significant difference was found in the total yield of organic acids between the three genotypes. Cluster analysis and principal component analysis identified a unique pea mutant SGECDt against the background of other genotypes with the joint introduction of salts of both heavy metals into the nutrient medium. A fractal analysis of the degree of structuredness of root exudation, using the example of the largest fraction of amino acids in terms of the number of components included in it, showed that the values of the correlation coefficients demonstrate an increase in the total plant biomass with a decrease in the indices of biosystemic determination. The lowest indicator of the plant system consolidation index in the absence of stress was found in the variety Sofya. Under the influence of HM, this numerical value did not change in any way, which may indicate the stagnation of plant growth and the transition to a state close to anabiosis. This can also be judged from the data of growth inhibition in the genotype and a decrease in the yield of amino acids. In the presence of HMs individually, the index of determination on pea SGE individually decreased, while in the SGECdt mutant, on the contrary, it increased. The combined effect of metals on SGECdt was multiplicative. Based on these indicators, it can be judged that the plant spends more energy to attract potential beneficial microflora in order to form an effective symbiosis and successfully counter metal-induced stress.