Phytotoxicity of the chiral herbicide dichlorprop: Cross-talk between nitric oxide, reactive oxygen species and phytohormones

Current advances and future trends of hormesis in disease

Hormesis, an adaptive response, occurs when exposure to low doses of a stressor potentially induces a stimulatory effect, while higher doses may inhibit it. This phenomenon is widely observed across various organisms and stressors, significantly advancing our understanding and inspiring further exploration of the beneficial effects of toxins at doses both below and beyond traditional thresholds. This has profound implications for promoting biological regulation at the cellular level and enhancing adaptability throughout the biosphere. Therefore, conducting bibliometric analysis in this field is crucial for accurately analyzing and summarizing its current research status. The results of the bibliometric analysis reveal a steady increase in the number of publications in this field over the years. The United States emerges as the leading country in both publication and citation numbers, with the journal Dose-Response publishing the highest number of papers in this area. Calabrese E.J. is a prominent person with significant contributions and influence among authors. Through keyword co-occurrence and trend analysis, current hotspots in this field are identified, primarily focusing on the relationship between hormesis, oxidative stress, and aging. Analysis of highly cited references predicts that future research trends may center around the relationship between hormesis and stress at different doses, as well as exploring the mechanisms and applications of hormesis. In conclusion, this review aims to visually represent hormesis-related research through bibliometric methods, uncovering emerging patterns and areas of focus within the field. It provides a summary of the current research status and forecasts trends in hormesis-related research.

The nexus between reactive oxygen species and the mechanism of action of herbicides

Herbicides are small molecules that act by inhibiting specific molecular target sites within primary plant metabolic pathways resulting in catastrophic and lethal consequences. The stress induced by herbicides generates reactive oxygen species (ROS), but little is known about the nexus between each herbicide mode of action (MoA) and their respective ability to induce ROS formation. Indeed, some herbicides cause dramatic surges in ROS levels as part of their primary MoA, whereas other herbicides may generate some ROS as a secondary effect of the stress they imposed on plants. In this review, we discuss the types of ROS and their respective reactivity and describe their involvement for each known MoA based on the new Herbicide Resistance Action Committee classification.

Novel Finding on How Melatonin and Nanoselenium Alleviate 2,4-D Butylate Stress in Wheat Plants

Nanoselenium (nano-Se) or melatonin (MT) foliar spray reduces pesticide stress by stimulating plant secondary metabolism and antioxidant capacity. However, the effects of nano-Se and MT biofortification on the interaction between plant secondary metabolic pathways and rhizosphere microbes in mitigating 2,4-D butyrate stress remain unknown. Compared to nano-Se or MT treatment alone, nano-Se and MT combined application increased the antioxidant enzyme activities and decreased the MDA (25.0%) and H2O2 (39.3%) contents with 2,4-D butylate exposure. Importantly, they enhance the soil enzymes (S-FDA by 53.1%), allelochemicals (luteolin by 164.1% and tricin by 147.3%), as well as plant secondary metabolites (JA by 63.3% and 193.3% in leaves and roots) levels. It also improved the beneficial microbial abundance of Comamonadaceae, Sphingomonadaceae, and Rhodobacteraceae in the rhizosphere soil. In conclusion, nano-Se and MT alleviate 2,4-D butylate stress in wheat plants by enabling the interaction between rhizosphere microorganisms, allelopathic substances, and secondary metabolites.

Bensulfuron-Methyl, Terbutylazine, and 2,4-D Butylate Disturb Plant Growth and Resistance by Deteriorating Rhizosphere Environment and Plant Secondary Metabolism in Wheat Seedlings

Frequent and improper use of herbicides disrupts a plant's metabolism, causing oxidative stress that degrades crop quality. However, few studies have examined the inhibitory effects of herbicides on plant growth and defense mechanisms in terms of their impact on soil quality and crop rhizosphere. Therefore, the current study investigated the detrimental impacts of six typical and multilevel herbicides on the microbial community and signal molecules in the soil as well as on the levels of hormones and secondary metabolites in wheat seedlings. Interestingly, bensulfuron-methyl, terbutylazine (TBA), and 2,4-D butylate significantly induced oxidative damage while reducing the number of phytohormones (salicylic acid and jasmonic acid) and secondary metabolites (tricin, quercetin, and caffeic acid) in the roots and leaves compared with the controls, isoproturon, fenoxaprop-p-ethyl, and pretilachlor. At twice the recommended levels (2×), they also decreased the microbial α diversity and, in particular, the abundance of Gammaproteobacteria, Alphaproteobacteria, Actinobacteria, Bacteroidia, Verrucomicrobia, Bacilli, Acidimicrobiia, Deltaproteobacteria, and Gemmatimonadetes by disrupting the level of enzymes (e.g., urease and sucrase) and metabolites (indole-3-acetic acid, salicylic acid, apigenin, 4-hydroxybenzoic acid, DIMBOA, and melatonin) in the rhizosphere soil. Overall, significant exposure to herbicides may inhibit wheat growth by disturbing the microbial composition in the rhizosphere soil and the distribution of secondary metabolites in wheat seedlings.

Nitric oxide, salicylic acid and oxidative stress: Is it a perfect equilateral triangle?

Nitric oxide (NO) is an endogenous free radical involved in the regulation of a wide array of physio-biochemical phenomena in plants. The biological activity of NO directly depend on its cellular concentration which usually changes under stress conditions, it participates in maintaining cellular redox equilibrium and regulating target checkpoints which control switches among development and stress. It is one of the key players in plant signalling and a plethora of evidence supports its crosstalk with other phytohormones. NO and salicylic acid (SA) cooperation is also of great physiological relevance, where NO modulates the immune response by regulating SA linked target proteins i.e., non-expressor of pathogenesis-related genes (NPR-1 and NPR-2) and Group D bZIP (basic leucine zipper domain transcription factor). Many experimental data suggest a functional cooperative role between NO and SA in mitigating the plant oxidative stress which suggests that these relationships could constitute a metabolic "equilateral triangle".

Physiological and oxidative stress responses of Solanum lycopersicum (L.) (tomato) when exposed to different chemical pesticides

Pesticide overuse can have negative effects on developmental processes of non-target host plants. By increasing reactive oxygen species (ROS) levels, pesticides negatively affect cellular metabolism, biochemistry and physiological machinery of plants. Considering these problems, the current study was planned to assess the effect of three different groups of pesticides, namely diazinon (DIZN), imidacloprid (IMID) and mancozeb (MNZB) on Solanum lycopersicum L. (tomato). In general, pesticides resulted in a progressive decrease in physiological and biometric parameters of S. lycopersicum (L.), which varies significantly among concentrations and species of pesticides. Among them, 200 μg_MNZB mL⁻¹ had the most severe negative impact and reduced germination rate, root biomass, chl a, chl b, total chlorophyll and carotenoids by 62, 87, 90, 88, 92 and 90%, respectively. In addition, higher doses of pesticides greatly reduced the flowering, fruit attributes and lycopene content. Furthermore, plants exposed to 200 μg_DIZN mL⁻¹ showed a progressive drop in root cell viability (54% decrease), total soluble sugar (TSS) (64% decrease) and total soluble protein (TSP) (67% decrease) content. Data analysis indicated that greater doses of pesticides dramatically raised ROS levels and induced membrane damage through production of thiobarbituric acid reactive substances (TBARS), as well as increased cell injury. To deal with pesticide-induced oxidative stress, plants subjected to greater pesticide dosages, showed a substantial increase in antioxidant levels. For instance, ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and guaiacol peroxidase (GPX) were maximally increased by 48, 93, 71, 52 and 94%, respectively following 200 μg_MNZB mL⁻¹ soil exposures. Additionally, under a confocal laser scanning microscope (CLSM), pesticide exposed S. lycopersicum (L.) roots stained with 2′,7′-dichlorodihydrofluorescein diacetate (2′7′-DCF) and 3,3′-diaminobenzidine, exhibited an increased ROS production in a concentration-dependent manner. Further, elevated pesticide concentrations resulted in alterations in mitochondrial membrane potential (ΔΨ_m) and cellular death in roots, as evidenced by increased Rhodamine 123 (Rhd 123) and Evan's blue fluorescence, respectively. These findings clearly showed that applying pesticides in excess of permissible amounts might induce oxidative stress and cause oxidative damage in non-target host plants. Overall, the current study indicates that a thorough and secure method be used before selecting pesticides for increasing production of agronomically important vegetable crops in various agro-climatic zones.

Pesticide overuse can have a negative effect on the development processes of non-target plants.