Two independent experiments were performed to investigate role of NO in 5-aminolevulinic acid-mediated resistance to lead toxicity in barley plants. Lead toxicity significantly resulted in reduction of plant growth, Fv/Fm, total chlorophyll, leaf water potential, and Ca2+ as well as K+ potassium levels. Concurrently, it resulted in elevated levels of leaf MDA, H2O2, EL, Pb, and NO in comparison to control group. Both ALA (50 µM and 100 µM; ALA1 and ALA2) treatments enhanced plant growth parameters and elevated leaf K+ and Ca2+ levels, while simultaneously decreasing leaf Pb, H2O2, and MDA concentrations in comparison to Pb-stressed plants. A second experiment was conducted to ascertain involvement of nitric oxide in mitigation of Pb stress in barley seedlings by ALA, utilizing nitric oxide scavenger C14H16N2O4.K (cPTIO) in conjunction with ALA treatments. ALA-induced tolerance to Pb stress was entirely negated by administration of cPTIO (C14H16N2O4.K), which significantly decreased concentrations of endogenous nitric oxide. The findings indicated that ALA improved resistance of barley seedlings to Pb toxicity via activating endogenous nitric oxide. This was corroborated by elevation of H2O2 and MDA levels, with a reduction in SOD, CAT, and POD activities. The application of cPTIO along with ALA, led to growth inhibition and a notable increase in leaf Pb concentrations. Both ALA and nitric oxide collaboratively enhanced Pb tolerance in barley.
Keywords: 5-aminolaevulinic acid; Antioxidant activities; Barley; Nitric oxide; Pb-toxicity.
© 2026. The Author(s), under exclusive licence to Springer Nature B.V.