Arsenic Toxicity in Cucurbita pepo L.: Concentration‐Dependent Growth, Metabolic and Antioxidant Responses

Summer squash ( Cucurbita pepo L.) is a vital vegetable. The short‐term physio‐biochemical responses of summer squash to severe arsenic (As) introduction remain inadequately characterised. A pot experiment was therefore conducted in sand‐based growing media to evaluate the concentration‐oriented responses of this crop to arsenic trioxide (As 2 O 3 ) at 0, 0.5 and 1.0 mM. Twenty‐day‐old As‐stressed plants were harvested and assessed for growth, photosynthetic pigments, oxidative injury, antioxidant defence and compatible osmolytes. These As concentrations were chosen to induce graded acute stress under controlled conditions. The experiment should not be taken as representative of a distinctive field‐based trial. Relative to the control (CK), 1 mM As reduced morpho‐physiological traits while increasing oxidative stress indicator levels. Moreover, in response to 1 mM As, total flavonoids, proline, phenolics and ascorbic acid increased, whereas free amino acids, soluble sugars, soluble proteins and anthocyanins declined. Catalase activity increased by 19% at 0.5 mM but declined below CK at 1.0 mM, while POX and APX increased most powerfully at 1.0 mM (103% and 197%, respectively). SOD activity also increased gradually, reaching about 162% above the CK at 1.0 mM. These corresponding responses indicate that acute As exposure disturbed carbon metabolism and photosynthetic functions. The environmental relevance of this physiological study should be authenticated using comparatively lower As concentrations for prolonged exposure periods.