Growth and biochemical parameters of Cicer arietinum L. grown on amended fly ash

Ascorbate glutathione antioxidant system alleviates fly ash stress by modulating growth physiology and biochemical responses in Solanum lycopersicum

Tomato plants (Solanum lycopersicum L.) were developed in soils with different fly ash (FA) amendments (25, 50, 75, 100% FA) to measure the effects of FA on metal accumulation, chlorophyll pigments, chlorophyll fluorescence, growth, biomass, gas exchange parameters, and the ascorbate glutathione pathway (AsA-GSH). The metal concentration was much higher in FA compared to the garden soil/(control). The observed metal translocation was higher in roots than shoots. Plants raised in soils treated with 50% or more FA showed significant decreases in growth, biomass, gas exchange parameters, protein, chlorophyll pigments, and fluorescence parameters. Additionally, a significant increase in antioxidants under higher FA-amended soils were observed. Our results showed that the ability of Solanum lycopersicum plants to effectively synchronize the actions of antioxidant enzymes associated in reactive oxygen species (ROS) scavenging - notably superoxidase dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR) - with good maintenance of the AsA/DHA ratio, that could be connected to FA stress tolerance. The toxic metals present in FA caused oxidative stress in Solanum lycopersicum, as evident from the increase in electrolyte leakage (EL), lipid peroxidation (MDA), and ROS levels. Furthermore, the AsA-GSH cycle plays a key role in alleviating oxidative damage caused by FA application.

Phytoremediation potential of naturally growing weed plants grown on fly ash-amended soil for restoration of fly ash deposit

Sida acuta Burm. f. and Cassia tora (L.) Roxb were identified as dominant plant species in fly ash deposit of NALCO, Koraput, India in our earlier study. However, little information is available on their physiological response to metal stress under fly ash amended soil. A pot experiment was designed with fly ash amended soil to assess its growth, photosynthesis, antioxidant defense along with metal accumulation. Addition of fly ash (50%) in soil amendments not only improved the soil physico-chemical characteristics but also increased the plant biomass. The studied plants were found to be a potential metal tolerant as metal tolerance index was more than 100% under fly ash amended soil. Leaf photosynthetic rate, chlorophyll content and photosystem II activity were not significantly changed under low level of fly ash amended soil (50%) compared to the garden soil. The induction of some antioxidative enzymes such as superoxide dismutase, ascorbate peroxidase, Guaiacol peroxidase and catalase in studied plants under elevated fly ash indicates metal tolerance ability of this plant to oxidative stress. Based on the bioaccumulation factor (BCF) and transfer factor (TF), these plants can be used for the remediation of Mn, Cu, Zn, Fe and Cr from fly ash.

Growth and physiological response of lemongrass (Cymbopogon citratus (D.C.) Stapf.) under different levels of fly ash-amended soil

Revegetation with metal tolerant plants for management of fly ash deposits is an important environmental perspective nowadays. Growth performance, photosynthesis, and antioxidant defense of lemongrass (Cymbopogon citratus (D.C.) Stapf.) were evaluated under various combination of fly ash amended with garden soil in order to assess its fly ash tolerance potential. Under low level of fly ash (25%) amended soil, the plant growth parameters such as shoot, root, and total plant biomass as well as metal tolerance index were increased compared to the control plants grown on garden soil, followed by decline under higher concentration of fly ash (50%, 75% and 100%). In addition, leaf photosynthetic rate, stomatal conductance, and photosystem (PS) II activity were not significantly changed under low level of fly ash (25%) amended soil compared to the garden soil but these parameters were significantly decreased further with increase of fly ash concentrations. Furthermore, increase of activities of some antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase over control were noticed in lemongrass under all fly ash treatments. Taken together, the study suggests that lemongrass can be used for phytoremediation of fly ash at 25% amended soil.

Comprehensive analysis of fly ash induced changes in physiological/growth parameters, DNA damage and oxidative stress over the life cycle of Brassica juncea and Brassica alba

Fly ash (FA) being a heterogeneous mixture of heavy metal affects plant system in various ways. Previous studies have shown bioaccumulation of toxic metals in the plants and disturbance in cellular activities. Here, we have studied the impacts of FA treatment through the life cycle of economically important, annual crop plant mustard (Brassica juncea and Brassica alba). Result revealed that FA did not alter germination rate and photosynthetic pigment levels. Tolerance index of B. juncea was higher compared to B. alba. Seed setting was significantly affected by FA in B. alba. Significant increase in DNA damage was observed in both B. alba and B. juncea. Proline accumulation was significantly higher in B. alba. In B. juncea catalase activity and reduced glutathione content declined in initial days which were restored at the end of experimental period. Significant decrease in non-enzymatic antioxidants was noted in B. alba. Higher accumulation of Pb and As was noted in shoot of B. juncea and in B. alba Cu, Pb, Cr and As accumulated in shoots. As observed from these results, both plants could translocate certain toxic heavy metals from roots to the shoot which affected the physiological and biochemical balance and induced genotoxic response.

Effect of Hg, As and Pb on biomass production, photosynthetic rate, nutrients uptake and phytochelatin induction in Pfaffia glomerata

Plantlets of Pfaffia glomerata (Spreng.) were exposed for 28 days to three different metal/metalloid (Hg, Pb and As) with different levels (Hg 1; As 25, 50, 100 and Pb 100 and 400 μM) to analyze the possible phytochelatin initiation and affects on growth and photosynthetic pigments vis-à-vis metal accumulation potential of plants. The plantlets showed significant Hg, As and Pb accumulation in roots (150, 1267.67 and 2129 μg g(-1) DW respectively); however, a low root to shoot metal translocation was observed. It was interesting to note that all tested macronutrient (Mg, K, Ca) was higher in shoots and just opposite in case of micronutrients (Cu, Fe, Zn), was recorded highest in roots. The growth of plantlets (analyzed in terms of length and dry weight) was negatively affected by various metal treatments. In addition, the level of photosynthetic pigments alters significantly in response to all metal/metalloid treatment. In response to all tested metal/metalloids in plants only As induced phytochelatins (PC2, PC3 and PC4) in roots, and in shoots, GSH was observed in all tested metal/metalloids. In conclusion, P. glomerata plantlets could not cooperatively induce phytochelatins under any of Hg and Pb levels.

Assessment of oxidative stress markers and concentrations of selected elements in the leaves of Cassia occidentalis growing wild on a coal fly ash basin

Assessment of oxidative stress levels and tissue concentrations of elements in plants growing wild on fly ash basins is critical for realistic hazard identification of fly ash disposal areas. Hitherto, levels of oxidative stress markers in plants growing wild on fly ash basins have not been adequately investigated. We report here concentrations of selected metal and metalloid elements and levels of oxidative stress markers in leaves of Cassia occidentalis growing wild on a fly ash basin (Badarpur Thermal Power Station site) and a reference site (Garhi Mandu Van site). Plants growing on the fly ash basin had significantly high foliar concentration of As, Ni, Pb and Se and low foliar concentration of Mn and Fe compared to the plants growing on the reference site. The plants inhabiting the fly ash basin showed signs of oxidative stress and had elevated levels of lipid peroxidation, electrolyte leakage from cells and low levels of chlorophyll a and total carotenoids compared to plants growing at the reference site. The levels of both protein thiols and nonprotein thiols were elevated in plants growing on the fly ash basin compared to plants growing on the reference site. However, no differences were observed in the levels of cysteine, reduced glutathione and oxidized glutathione in plants growing at both the sites. Our study suggests that: (1) fly ash triggers oxidative stress responses in plants growing wild on fly ash basin, and (2) elevated levels of protein thiols and nonprotein thiols may have a role in protecting the plants from environmental stress.

Dose-related effect of fly ash on edaphic properties in laterite cropland soil

Short-term laboratory and field studies showed dose-based effect of coal fly ash on chemical and microbial properties of laterite cropland soil. Sandy loam soil mixed with farmyard manure (10% w/w) and amended with fly ash at 5%, 10%, 20%, 40% w/w (50-400 t ha(-1)) was incubated in the laboratory and added to field plots. The pH, EC, PO(4), Ca and Na of soil increased with dose and time, but OC, NO(3) and K decreased. There was temporary inhibition of bacteria, fungi and actinomycetes populations at 5% and 10% doses, but 20% and 40% were harmful. Activities of major soil enzymes declined at higher doses. Amylase, cellulase and invertase recovered in 5% and 10%, these doses did not affect dehydrogenase but benefited phosphatase and arylsulphatase activities. The above assessments showed that up to 100 t ha(-1) fly ash is apparently safe to microbial characteristics of tropical red laterite soil.