Hydrolytic enzymes mediated lipid-DNA catabolism and altered gene expression of antioxidants under combined application of lead and simulated acid rain in Fenugreek (Trigonella foenum graecum L.) seedlings

Unveiling Innovative Approaches to Mitigate Metals/Metalloids Toxicity for Sustainable Agriculture

Due to anthropogenic activities, environmental pollution of heavy metals/metalloids (HMs) has increased and received growing attention in recent decades. Plants growing in HM-contaminated soils have slower growth and development, resulting in lower agricultural yield. Exposure to HMs leads to the generation of free radicals (oxidative stress), which alters plant morpho-physiological and biochemical pathways at the cellular and tissue levels. Plants have evolved complex defense mechanisms to avoid or tolerate the toxic effects of HMs, including HMs absorption and accumulation in cell organelles, immobilization by forming complexes with organic chelates, extraction via numerous transporters, ion channels, signaling cascades, and transcription elements, among others. Nonetheless, these internal defensive mechanisms are insufficient to overcome HMs toxicity. Therefore, unveiling HMs adaptation and tolerance mechanisms is necessary for sustainable agriculture. Recent breakthroughs in cutting-edge approaches such as phytohormone and gasotransmitters application, nanotechnology, omics, and genetic engineering tools have identified molecular regulators linked to HMs tolerance, which may be applied to generate HMs-tolerant future plants. This review summarizes numerous systems that plants have adapted to resist HMs toxicity, such as physiological, biochemical, and molecular responses. Diverse adaptation strategies have also been comprehensively presented to advance plant resilience to HMs toxicity that could enable sustainable agricultural production.

Lead absorption capacity in different parts of plants and its influencing factors: a systematic review and meta-analysis

People pose a serious risk by plants contaminated with lead in soil. However, the strength of lead enrichment capacity in root, stem, and leaf of the plant is still controversial. Therefore, a meta-analysis was conducted to investigate the ability of lead enrichment of root, stem, and leaf and the main influencing factors for lead absorption. The results of this study indicated that all parts of plant can significantly accumulate lead. Concentrations of lead followed an order of root > stem > leaf. Alkaline soil was conducive to the absorption of lead. When the lead concentration in the soil was higher than 20 mg/kg, the lead absorption in root was more. Lead is absorbed most in trees and least in Gramineae. It is argued that this study is beneficial to select plants suitable for absorption of lead from polluted soil. This study also can help to clarify the influencing factors for lead enrichment in different parts of the plant.

Chitosan Functionalized with 2-Methylpyridine Cross-Linker Cellulose to Adsorb Pb(II) from Water

In this study, chitosan was chemically modified with 2-methylpyridine. Subsequently, the modified chitosan was cross-linked to cellulose using succinic anhydride. Additionally, the capacity of cellulose derivatives to adsorb Pb(II) ions in an aqueous solution was studied through the determination of Pb(II) ions concentration in water, using microwave plasma atomic emission spectroscopy (MP-AES). A maximum adsorption capacity of 6.62, 43.14, 60.6, and 80.26 mg/g was found for cellulose, cellulose-succinic acid, cellulose-chitosan, and cellulose-chitosan-pyridine, respectively. The kinetic data analysis of the adsorption process showed a pseudo-second-order behavior. The increase in metal removal from water is possibly due to metal chelation with the carbonyl group of succinic acid, and the pyridine groups incorporated into chitosan.

Calcium regulates antioxidative isozyme activity for enhancing rice adaption to acid rain stress

Acid rain, as a typical abiotic stress, damages plant growth and production. Calcium (Ca) mediates plant growth and links the signal transduction in plants for adapting to abiotic stresses. To understand the effect of Ca²⁺ on plant adaptable response to acid rain, we investigated changes in activities and gene expression of antioxidative enzymes and fatty acid composition of membrane lipid in rice seedlings treated with exogenous Ca²⁺ (5 mM) or/and simulated acid rain (SAR, pH 3.5 / 2.5). Exogenous Ca²⁺ enhanced activities of superoxide dismutase, catalase and peroxidase isozymes in rice leaves under SAR stress by promoting activation of existing isoforms and up-regulation of Cu/Zn-SOD1, Cu/Zn-SOD2, Cu/Zn-SOD3, CAT1, CAT2 and POD1. Compared to SAR treatment alone, exogenous Ca²⁺ alleviated SAR-induced oxidative damage to cell membrane by enhancing antioxidative capacity, as shown by the decrease in concentrations of H₂O₂, O₂^- and malondialdehyde in rice leaves. Meanwhile, Ca²⁺ alleviated SAR-induced decrease in unsaturation of membrane lipid for maintaining membrane fluidity. Finally, exogenous Ca²⁺ alleviated SAR-induced inhibition on relative growth rate of rice. Therefore, Ca²⁺ could play a role in regulating activities of antioxidative enzymes as well as maintaining unsaturation of membrane lipid for enhancing tolerance in rice seedlings to acid rain stress.

Titanium nanoparticles attenuates arsenic toxicity by up-regulating expressions of defensive genes in Vigna radiata L

Arsenic (As)-toxicity is recognized as one of the major environmental problems, affecting productivity of crops worldwide, thereby threatening sustainable agriculture and food security. Progression in nanotechnology and its impacts have brought up concerns about the application of engineered nanoparticles (NPs) in various sectors of the economy, including the field of agronomy. Among various NPs, there has been a rising amount of interest regarding the effects of titanium NPs (TiNPs) on plants growth and development, and their fate of abiotic stress tolerance. Hence, the present study was aimed to assess the ameliorative potentialities of chemically and biologically/green synthesized TiNPs to alleviate As-induced toxic responses in Vigna radiata L. The results revealed that exposure to As hindered the growth indices (radicle length and biomass) and membrane integrity, while were improved with the application of chemical and green synthesized TiNPs. In addition, treatment of As provoked the accretion of reactive oxygen species (superoxide and hydrogen peroxide) and malondialdehyde (a lipid peroxidized product), but were diminished by the supplementation of chemical and green manufactured TiNPs. The experimental data also signified that exogenous application of chemical and green synthesized TiNPs conferred tolerance to As-induced oxidative injuries via perking-up the expressions of antioxidant genes and enzyme systems viz; superoxide dismutase and catalase. Therefore, the present study inferred that chemically and green synthesized TiNPs, particularly green manufactured, effectively mitigated the adverse impacts of As by augmenting antioxidant machinery, thereby proving its potentiality in the alleviation of As-toxicity, at least in Vignaradiata L.

Toxic effects of lead in plants grown in brazilian soils

Lead (Pb) in soils can be transferred to plants, animals, and even humans. The toxicity of Pb is worrisome and therefore environmental quality criteria, established by laws to support the management of contaminated sites, have been developed to prevent its deleterious effects in a wide range of soils, uses, and occupations. In Brazil, the CONAMA Resolution 420/2009 established that Brazilian states may define their prevention values (PV) for metals in soils. However, the established values should be well studied, since a wide variation of sensitivity of species exposed to Pb is reported and several have a high tolerance. We aimed to evaluate Pb toxicity to validate the suitability of the current Brazilian Pb-prevention value. A trial was carried with two plant species (sorghum and soybean) grown in two tropical soils (Typic Hapludox and Rhodic Acrudox), following ISO 11.269-2 protocols (ISO 2012). The tested soils were contaminated with Pb-acetate at the following concentrations: 0, 200, 400, 800, 1200, 1600, 2200, 2800, and 3200 mg kg^-1 of dry soil. Differences regarding species sensitivity were observed and sorghum seemed to be less sensitive to Pb concentration in soils. Soil characteristics as higher clay and organic matter content were responsible for decreasing the overall availability of Pb for plants. Using data from this study and from the literature, we constructed a species sensitivity distribution curve and calculated the HC5 (hazardous concentration to 5% of variables evaluated). The HC5 was 132.5 mg kg^-1, which suggests that the PV currently used in Brazil (72 mg kg^-1) is sufficiently protective for Brazilian soils.

Melatonin, glutathione and thiourea attenuates lead and acid rain-induced deleterious responses by regulating gene expression of antioxidants in Trigonella foenum graecum L

Lead and acid rain are important abiotic stress factors that limit the growth, development, metabolic activity and yield of the crops. Melatonin (MT; an indoleamine molecule), glutathione (GSH; free thiol tripeptide) and thiourea (TU; non physiological thiol based ROS scavenger) have been known to mediate several physiological, biochemical and molecular processes in plants under different kinds of environmental threats. However, the roles of MT, GSH and TU in stress tolerance against combined effect of lead and simulated acid rain (SAR) remains inexpressible. In this study, we investigated the response of Trigonella foenum graecum L. (Fenugreek) to combined application of lead (1200 ppm) and SAR (pH 3.5), and the potential roles of MT (50 μM), GSH (1 mM) and TU (3 mM) in enhancing lead and SAR stress tolerance of Fenugreek. The results showed that co-application of each MT, GSH and TU along with lead and SAR improved the growth and development of seedlings. Moreover, MT, GSH and TU treatments stabilized the cell membrane integrity, reduced ROS accumulation [superoxide radical (O₂-) and hydrogen peroxide (H₂O₂)], malondialdehyde (MDA) content, lipoxygenase (LOX) activity and, enhanced protein accumulation and up-regulated the gene expressions of catalase (CAT) and superoxide dismutase (SOD) significantly. Furthermore, the present work provides strong evidence regarding protective roles of MT, GSH and TU against oxidative stress resulted from lead and SAR stress in Fenugreek. Considering these observations, MT, GSH and TU can be utilized as efficient ROS scavengers, for improving growth and increasing antioxidant capacity in lead and SAR stressed seedlings.