Soil contamination by chromium (Cr) has severely degraded soil the health, which poses a serious threat to sustainable agricultural production worldwide. This present study investigated the combined application of Aloe vera gel and selenium nanoparticles (Se-NPs) to enhance the phytoremediation potential of spinach grown in a Cr-contaminated soil. It was hypothesized that the combined use of Se-NPs and Aloe vera gel would reduce Cr toxicity in spinach via improving the antioxidant defense system. A pot experiment was conducted to assess the role of Aloe vera gel seed priming and foliar applied selenium (Se) to alleviate the Cr-induced stress in spinach plants. The current experiment followed a completely randomized design (CRD) and consisted of two factors: factor A included treatments with and without Aloe vera gel as its seed priming application, and factor B included foliar application of the Se-NPs at different levels (0, 0.5, 1.0, and 2 mg/L). Each experimental treatment was replicated three times. A two-way analysis of variance (ANOVA) was performed using Statistix 8.1, while correlation analysis, heat map visualization and principal component analysis (PCA) was performed using R-Software. The Se-NPs and Aloe vera gel significantly increased biomass by up to 48%, chlorophyll a by 37%, soluble protein by 99% and reduced malondialdehyde and electrolyte leakage (EL) by over 40% at 2 mg L - ¹ Se NPs (P ≤ 0.05). Combined Aloe vera and Se NPs also restricted the Cr accumulation in leafy parts of spinach plants. Cr inhibited spinach growth and reduced photosynthesis by inducing over-production of the ROS and negatively affected the antioxidant defense system. However, the combined application of Se-NPs and Aloe vera gel significantly enhanced spinach growth and photosynthesis, alleviating Cr-induced stress through scavenging ROS by strengthening the plant anti-oxidative defense system, while Cr level remained under the threshold level (1.30 µg/g). The use of NPs represents an eco-friendly and cost-effective approach, which may serve as a green alternative to conventional methods used for heavy metal remediation. Mechanistically, these improvements were linked to up-regulation of the antioxidant enzymes and reduced accumulation of the ROS, suggesting enhanced redox homeostasis under stressful conditions. Our results demonstrate that the combined treatment of Se-NPs and Aloe vera gel significantly enhances spinach tolerance to chromium toxicity and is a good approach to promote phytoremediation and crop production in contaminated soils.
Sajjad et al. (Wed,) studied this question.