Evaluating water deficit and glyphosate treatment on the accumulation of phenolic compounds and photosynthesis rate in transgenic Codonopsis lanceolata (Siebold & Zucc.) Trautv. over-expressing γ-tocopherol methyltransferase (γ-tmt) gene

Effects of different eco-stoichiometric ratios of calcium and cadmium on the detoxification mechanisms of Capsicum annuum L. under cadmium stress

The eco-stoichiometry of Ca/Cd in soil significantly affects Cd uptake and accumulation by plants in carbonate regions. In this study, the physiological responses and detoxification mechanisms of Capsicum annuum L. (capsicum) were investigated based on the eco-stoichiometric relationship of Ca/Cd in production substrates under varying pH levels (5, 6, and 7). The results revealed that increased Ca/Cd ratio enhanced the Cd accumulation in roots at pH values of 5 and 6. The enrichment of Cd in stems and leaves gradually decreased with varying Ca/Cd ratios at different pH levels. In addition, root vigor, relative chlorophyll content, biomass, and catalase and peroxidase activities increased across various pH levels, while the concentration of protein carbonyl and malondialdehyde decreased. The ability of pectin and cellulose in the cell wall and that of soluble components within the cell to adsorb and partition Cd improved as the Ca/Cd ratio increased at different pH values. Notably, the effects of varying Ca/Cd ratios were most significant at pH 6. Overall, Ca enhanced the tolerance of capsicum to Cd stress, thereby promoting the fixation of Cd in root cells, reducing its transfer to aboveground tissues, and improving both the growth and antioxidant stress response. The effect was attributed to different Ca/Cd stoichiometric ratios, pH levels, and their interactions. These findings enhance the understanding of the mechanism of the interaction between Ca and Cd on crops in the karst agroecosystem.

Effect of splitting the sub-lethal dose of glyphosate on plant growth shikimate pathway-related metabolites and antioxidant status in faba beans

Glyphosate exerts its herbicidal activity by inhibiting the shikimate pathway, the main source of many primary and secondary metabolites. Application of a low dose of glyphosate to faba bean plants was effective in controlling Orobanche crenata infestation, but some toxic effects on host plants can occur. Splitting the low glyphosate dose can serve as a mitigation strategy to reduce the host toxicity. Under parasitic-free conditions, a greenhouse experiment was conducted during two seasons to study the effect of dividing the recommended glyphosate dose (170 g a.i. ha-1) into two-five sprays on the growth, shikimate-related metabolites, and antioxidant status of three faba bean varieties. After 40 days, splitting treatments tended to cause cumulative inhibition effects on the growth and productivity traits of faba beans depending on the tested varieties, seasons, and the number of sprays applied. The maximum reduction effect was noticed for twice- sprayed treatment in the first season and for five-sprayed treatment in the second one. The cumulative effect of splitting glyphosate treatments on the shikimate pathway metabolites and the antioxidant status was measured after a week of spraying. Splitting treatments induced great increases in shikimic acid and phenylalanine contents compared with control. These treatments continued to exert their oxidative stress on faba bean plants by reducing antioxidant activity and antioxidant compounds such as total phenolics, flavonoids, and the detected phenolic acids (p-hydroxybenzoic, syringic, vanillic, coumaric, and ferulic). A significant increase in the activities of antioxidant enzymes (superoxide dismutase, peroxidase, and polyphenol oxidase) was recorded for all splitting treatments.

Herbicide resistance status impacts the profile of non-anthocyanin polyphenolics and some phytomedical properties of edible cornflower (Centaurea cyanus L.) flowers

To ensure sufficient food supply worldwide, plants are treated with pesticides to provide protection against pathogens and pests. Herbicides are the most commonly utilised pesticides, used to reduce the growth of weeds. However, their long-term use has resulted in the emergence of herbicide-resistant biotypes in many weed species. Cornflower (Centaurea cyanus L., Asteraceae) is one of these plants, whose biotypes resistant to herbicides from the group of acetolactate synthase (ALS) inhibitors have begun to emerge in recent years. Some plants, although undesirable in crops and considered as weeds, are of great importance in phytomedicine and food production, and characterised by a high content of health-promoting substances, including antioxidants. Our study aimed to investigate how the acquisition of herbicide resistance affects the health-promoting properties of plants on the example of cornflower, as well as how they are affected by herbicide treatment. To this end, we analysed non-anthocyanin polyphenols and antioxidant capacity in flowers of C. cyanus from herbicide-resistant and susceptible biotypes. Our results indicated significant compositional changes associated with an increase in the content of substances and activities that have health-promoting properties. High antioxidant activity and higher total phenolic and flavonoid compounds as well as reducing power were observed in resistant biotypes. The latter one increased additionally after herbicide treatment which might also suggest their role in the resistance acquisition mechanism. Overall, these results show that the herbicide resistance development, although unfavourable to crop production, may paradoxically have very positive effects for medicinal plants such as cornflower.

Unravelling the Phytotoxic Effects of Glyphosate on Sensitive and Resistant Amaranthus palmeri Populations by GC-MS and LC-MS Metabolic Profiling

Glyphosate, the most successful herbicide in history, specifically inhibits the activity of the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS; EC 2.5.1.19), one of the key enzymes in the shikimate pathway. Amaranthus palmeri is a driver weed in agriculture today that has evolved glyphosate-resistance through increased EPSPS gene copy number and other mechanisms. Non-targeted GC-MS and LC-MS metabolomic profiling was conducted to examine the innate physiology and the glyphosate-induced perturbations in one sensitive and one resistant (by EPSPS amplification) population of A. palmeri. In the absence of glyphosate treatment, the metabolic profile of both populations was very similar. The comparison between the effects of sublethal and lethal doses on sensitive and resistant populations suggests that lethality of the herbicide is associated with an amino acid pool imbalance and accumulation of the metabolites of the shikimate pathway upstream from EPSPS. Ferulic acid and its derivatives were accumulated in treated plants of both populations, while quercetin and its derivative contents were only lower in the resistant plants treated with glyphosate.