Physiological Effects of Chromium (Cr) on <i>Spinacia oleracea L.</i> under Controlled Conditions

Heavy metal contamination in agricultural soils is a significant environmental concern that jeopardises crop yield and food safety. This study examined the phytotoxic effects of hexavalent chromium (Cr⁶⁺), provided as potassium dichromate (K₂Cr₂O₇), on many physiological parameters of Spinacia oleracea L. (spinach). Plants were subjected to several doses of Cr (0, 50, 100, and 150 mg/L) in a controlled environment. The findings indicated a concentration-dependent reduction in germination %, root and shoot lengths, leaf area, biomass (both fresh and dry weight), and chlorophyll content. In contrast, proline accumulation rose considerably under Cr stress, demonstrating an active physiological response to metal-induced oxidative stress. The highest level of chromium (150 mg/L) caused a 30.76% drop in germination, a 41.5% drop in total chlorophyll, and a 71.2% rise in proline content compared to the control. These results indicate that Cr stress adversely affects spinach growth and metabolism, but proline accumulation may function as a protective adaptation strategy. The study underscores the susceptibility of spinach to chromium toxicity and advocates for its possible application as a bioindicator for environmental monitoring in damaged agroecosystems.