Abscisic acid alleviates cadmium toxicity in oilseed rape plants by regulating its accumulation, subcellular distribution, and ascorbate-glutathione cycle

Soil cadmium (Cd) contamination threatens agricultural productivity and food safety by impairing plant physiological processes. This study aimed to investigate the role of abscisic acid (ABA) in mitigating Cd toxicity in oilseed rape ( Brassica napus L.), an economically important oil crop. Hydroponic experiments were conducted with two B. napus accessions ZA334 (Cd-sensitive) and ZA106 (Cd-tolerant) to examine plant growth, oxidative stress, Cd accumulation, subcellular distribution, chemical speciation, and antioxidant metabolism under Cd stress. Application of 0.5 μM ABA significantly reduced Cd-induced growth inhibition and oxidative damage, lowered Cd accumulation in shoots and roots, increased Cd sequestration in cell walls, and decreased mobile Cd fractions. ABA also enhanced antioxidant enzyme activities and promoted ascorbic acid (AsA) and glutathione (GSH) regeneration via the AsA-GSH cycle. The GSH/glutathione disulfide ratios in shoots and roots increased by 97.9% and 85.0% in ZA334 and 79.8% and 135.6% in ZA106, respectively, while the AsA/dehydroascorbic acid ratios increased by 20.7% and 20.6% in ZA334 and 16.4% and 20.7% in ZA106, respectively. These findings demonstrated that ABA mitigates Cd toxicity by regulating Cd uptake, distribution, and enhancing antioxidant defense, offering a promising strategy for improving Cd tolerance in oilseed rape. • ABA alleviates cadmium-induced growth inhibition in oilseed rape. • ABA reduces Cd uptake, promotes Cd sequestrations in cell walls, and decreases mobile Cd fractions. • ABA enhances antioxidant enzyme activities under Cd stress. • ABA strengthens AsA–GSH cycle to maintain cellular redox homeostasis.