Caffeic acid (CA) is known as an antioxidant to scavenge reactive oxygen species (ROS), but the underlying mechanism of mediation of plant salt tolerance against various abiotic stresses by caffeic acid is only partially understood. A field experiment (120 days duration) was conducted to investigate the protective role of caffeic acid under a high saline medium (EC 8.7 dS m ^-1 and textural class: sandy loam) in two wheat genotypes (FSD -08 and Zincol-16). Two levels of caffeic acid (50 μM and 100 μM) were applied exogenously in combination with the salinity stress and results revealed that salt alleviation is more prominent when caffeic acid was applied at the rate of 100 μM. Under saline conditions, wheat genotypes show poor fresh and dry matter accumulation, chlorophyll contents, relative water contents (RWC), membrane stability index (MSI) and activities of antioxidant enzymes and increased uptake of Na ⁺ ions. However, wheat genotype FSD-08 eminently responded to caffeic acid application as compared to wheat genotype Zincol-16 as demonstrated by higher growth indicators, RWC, MSI, activities of antioxidant enzymes, accumulation of mineral ions in grain along with yield attributes. In addition, caffeic acid also mitigated salt-induced oxidative stress malondialdehyde (MDA) and hydrogen peroxide (H ₂ O ₂ ) contents as well as significantly reduced Na ⁺ uptake. It can be concluded that caffeic acid-induced salinity tolerance in wheat is attributed to improved plant water relations, K ⁺ uptake, yield contents and activities of antioxidant stress enzymes.

Heavy metal (HMs) toxicity has severely impacted wheat production and is considered an emerging threat to human health due to bioaccumulation. The application of organic and inorganic amendments has proven effective in mitigating HM’s phytotoxicity by limiting their mobility in soil and plants. A pot experiment was conducted to evaluate the efficiency of biochar (BC), bentonite (BN), and rock phosphate (RP), both individually and in combination, in alleviating lead (Pb) toxicity and enhancing wheat growth, and physiological attributes. The present investigation revealed that BC, BN, RP, and their combined mineral biochar amendments (MBAs) at 1.5% level significantly enhanced wheat growth along with reducing DTPA-extractable Pb in soil by 30.0–49.8% and Pb uptake in roots by 15.7–37.5% and in shoots by 34.5–48.5%. Antioxidant enzymatic activities were improved, and stress indicators were reduced in roots and shoots of wheat under Pb stress, including hydrogen peroxide (H₂O₂) by 50.7 and 81.0%, malondialdehyde (MDA) levels by 16.0 and 74.9%, and proline content by 34.5 and 64.0%, respectively. The effectiveness of the treatments is described in descending order viz. MBA-1 > MBA-3 > MBA-2 > BC > RP > BN under Pb stress. In conclusion, the integration of biochar, bentonite, and rock phosphate is a promising strategy for sustainable and cleaner cereal crop production under heavy metal stress conditions.

Heavy metal toxicity disrupts plant cellular homeostasis by inducing oxidative stress and impairing the key signaling networks that regulate plant growth and defense. Small signaling metabolites, such as pipecolic acid (PipA), a known regulator of systemic acquired resistance, may play a critical role in modulating plant responses to abiotic stresses. This study investigated the signaling and physiological roles of exogenously applied PipA in mitigating lead (Pb)-induced phytotoxicity in chili (Capsicum annuum L.). Eight treatments comprising an absolute control, Pb stress alone (800 mg kg⁻¹ soil) and single or combined PipA applications (0.5 mM via seed priming, soil drenching, and foliar spray) were administered in homogenized soil media. Lead stress alone drastically impaired plant performance, as the root length decreased by 45.9%, shoot length decreased by 45.8%, total yield decreased by 46.7%, relative water content (RWC) decreased by 32.11%, membrane stability index (MSI) decreased by 42.07%, photosynthetic rate (Pn) decreased by 56.86%, stomatal conductance (gs) decreased by 57.01%, malondialdehyde (MDA) concentration increased by 237.92%, hydrogen peroxide (H₂O₂) accumulation increased by 260.71%, fruit length decreased by 48.38%, vitamin C concentration decreased by 39.92%, and root lead accumulation increased by 73525.21%. In contrast, combined PipA applications significantly reversed these deteriorations, particularly those resulting from seed priming and foliar spray, which increased the root length by 35.94%, enhanced Pn by 105.36%, elevated the gs by 113.76%, and reduced the contents of MDA by 60.54 and also reduced the form of accumulated H₂O₂ by 63.37% relative to that in stressed plants. Dual delivery systems are synergistic in activating antioxidant enzymes, stabilizing membranes, optimizing gas exchange, and minimizing heavy metal translocation. PipA supplementation showed beneficial effects on reprogramming stress-responsive pathways and holds promise for enhancing crop resilience under chronic metal stress conditions. Reclaiming (polluted) agroecosystems should be accomplished through the adoption of integrated bioremediation protocols using exogenous PipA. Collectively, the evidence suggests that combining both exogenous PipA application methods (initial treatment via seed priming and subsequent treatment via foliage) is a viable, biologically compatible, and practical/flexible way to overcome Pb-induced physiological effects on crop yield in contaminated agricultural ecosystems.