Morpho-Physiological Response of Napier Grass (Cenchrus purpureus (Schumach.) Morrone) Under Chromium Stress: Role of Ascophyllum nodosum-Based Biostimulants

Abstract

Chromium (Cr) pollution from mining activities severely impairs soil health and plant productivity. This research assessed the phytoremediation potential of Cenchrus purpureus (Napier grass) grown in progressively increasing mixtures of overburden (OB) dump soil from Sukinda chromite mines (0 to 100%, i.e., designated T0 to T10), comparing plants treated (NP + ANBz) and untreated (NP) with foliar application of Ascophyllum nodosum-based biozyme (ANBz, 10% w/v). Following 30 days of exposure, Cr stress substantially diminished growth parameters, photosynthetic pigments, protein levels, and carbohydrate contents, while upregulating antioxidant enzyme activities. The key insight is that foliar application of ANBz alleviates Cr-induced trade-offs between antioxidant defence and biomass production, thereby enhancing phytostabilization through greater root Cr sequestration and stress tolerance in dose-dependent treatments. Compared to untreated plants, ANBz increased biomass by 47.05-76.15%, chlorophyll content by 35.38-87.32%, protein by 0.54-93.44%, and carbohydrates by 20.77-74.8%. Furthermore, ANBz amplified activities of catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX), further alleviating damage from oxidative stress. Cr primarily accumulated in roots (BCF > 1), with minimal shoot translocation (TF < 1; BAF < 1), suggesting phytostabilisation as the dominant remediation strategy. [GRAPHICS]