Effect of Soil-Dwelling Fungi on the Seedlings of Sorghum in the Presence of Polycyclic Aromatic Hydrocarbons

Morphometric, physiological, and biochemical characteristics were determined in the seedlings of Sorghum bicolor (L.) Moench treated with natural metabolites of soil-dwelling fungi Fusarium oxysporum (Schlecht. emend. Snyder & Hansen) and Stropharia rugosoannulata (Farlow ex Murrill), polycyclic aromatic hydrocarbons (PAHs) pyrene and fluoranthene, and the products of their fungal degradation. The obtained results showed that the effect of fungal culture liquids (CLs) on plants depended on the duration of culturing. In the case of S. rugosoannulata, the inhibitory effect intensified, while the stimulatory effect became stronger (except for germinating capacity) in the case of F. oxysporum. Fungal CLs and native PAHs augmented peroxidase activity in sorghum seedlings three to seven times as compared with control material. Duration of culturing of the fungi exerted a considerable and reverse influence on the pattern of changes in sorghum peroxidase activity in response to CLs of Stropharia and Fusarium. The presence of PAHs and the products of their fungal degradation considerably modified some parameters, especially characteristic of F. oxysporum. The effect of fluoranthene in its CL, which stimulated shoot growth and almost doubled shoot weight, with peroxidase activity decreasing more than two times, was most pronounced. Revealed differences in the effect of fungal metabolites on the seedlings of sorghum may be related to different ecological strategies of fungi and production therein of various biologically active compounds, which causes corresponding plant responses on morphological, physiological, and biochemical levels. Considerable changes in some characteristics occurring in the presence of PAHs and their derivatives point to an appreciable influence of environmental pollutants on interactions between the organisms.