Assessment of mechanisms underlying flyash-mediated control of oxidative stress and antioxidant metabolism in Vicia faba L.

Abstract Globally, increasing coal-fired power production has resulted in large accumulations of coal combustion byproducts such as fly ash, widely recognized as a valuable soil ameliorant. Taking into account bakla (Vicia faba L.) in greenhouse experiments, this study aimed to assess the effects of soils amended with fly ash (FA; 0% 5%, 10%, 20%, 30%, 40% and 50%) on the plant growth characteristics and the major photosynthesis variables [(including chlorophyll content; stomatal behavior; activity of carbonic anhydrase (CA), a chloroplast-localized metalloenzyme)]; activity of nitrate reductase (NR), a rate-limiting enzyme of nitrogen metabolism; damage indicators [reactive oxygen species (ROS); and malondialdehyde (MDA), a lipid peroxidation product; and cell viability); and also to evaluate the role of defense characteristics such as proline (a nitrogenous osmolyte), and the major enzymes involved in dismutation of superoxide (superoxide dismutase, SOD); metabolism of H2O2–metabolism (catalase, CAT), and in peroxide-cleaving redox reactions (peroxidase, POX). Measurements were done at 45 days after sowing (DAS). Among the FA-proportions tested, 40 and 50% FA caused significant decreases in plant growth characteristics namely shoot length, root length, plant fresh and dry weight, and leaf area; photosynthesis variables including chlorophyll content, stomatal behavior (aperture size, shape and frequency of stomata); activity of CA and NR, and the viability of cells. These decreases in the mentioned parameters were corroborated with increases in ROS and MDA contents. However, when grown in soils amended with 5%, 10%, 20% and 30% FA, V. faba plants exhibited improvements in the mentioned parameters of growth and photosynthesis, and stomata; and cell viability; which were accompanied with the decreased contents of ROS and MDA, and coordinated increases in the activity of SOD, CAT and POX. Given the protective role of lower concentrations of FA (5%, 10%, 20% and 30%) in V. faba, these FA concentrations may be utilized as a fertilizer in sustainably improving the health and productivity of vegetable crops.