Prohexadione calcium enhances physiological and biochemical resilience of a vegetable crop under dual abiotic–xenobiotic stress

Abstract

Abiotic and xenobiotic stresses represent critical agro-environmental challenges that impair crop productivity and food safety. Although their individual impacts are documented, the synergistic effects of dual salinity+aniline stress and the potential mitigating role of prohexadione calcium (PHDC) remain poorly understood. In this study, plants were exposed to a sodium salt mixture (NaCl + Na₂SO₄ in 1:1 ratio; 75 mM each, total 150 mM) (abiotic stress), a mixture of aniline derivatives (50 mg L⁻¹ aniline hydrochloride + 50 mg L⁻¹ aniline sulfate; total 100 mg L⁻¹) (xenobiotic stress), and their combination, with or without foliar application of 100 mg L⁻¹ prohexadione calcium. The experiment was conducted on Brassica oleracea var. italica using popular cultivars such as Green Magic, in a completely randomized design with four replicates per treatment. PHDC was applied as a foliar spray, and data were analyzed using two-way ANOVA followed by Tukey’s HSD test to assess main and interaction effects. Physiological and biochemical data revealed that mixed sodium salt stress (NaCl + Na₂SO₄, 150 mM total) and mixed aniline stress (100 mg L⁻¹ total) independently reduced shoot biomass by 28–32%, chlorophyll content by 25–30%, and soluble protein levels by 22–27% relative to the untreated control plants, while elevating malondialdehyde and hydrogen peroxide accumulation by 40–45%. The combined salinity + aniline stress imposed the most severe damage, reducing shoot biomass by 42%, root biomass by 38%, and leaf area by 45% compared to the control. Application of prohexadione calcium (PHDC; 100 mg L⁻¹ foliar spray) significantly alleviated these impairments. Under combined stress, PHDC-treated plants showed recovery, with shoot biomass increased by 36%, root biomass by 32%, and leaf area by 40% relative to stressed plants without PHDC treatment. PHDC also restored pigment concentrations, elevating chlorophyll a, chlorophyll b, and total chlorophyll by 30–36% compared to untreated stressed plants. In terms of osmolytes, PHDC enhanced proline accumulation by 38% and soluble sugars by 42% relative to stressed plants without PHDC, while reinforcing antioxidant defenses by increasing SOD, CAT, and POD activities by 30–35%. Nutrient status, particularly nitrogen, potassium, and calcium, was also improved under combined stress with PHDC treatment. The protective effect was most pronounced under combined stress, underscoring PHDC’s role in modulating resilience pathways. This study is distinctive because it evaluates prohexadione calcium under dual abiotic–xenobiotic stress, a combination rarely investigated in vegetable crops, thereby providing integrative physiological and biochemical evidence beyond previous single-stress or single-species reports.