Silicon alleviates cadmium stress by improving growth, physiological performance, and cellular integrity in broccoli

Broccoli (Brassica oleracea var. italica) is considered an important vegetable crop valued for its high nutritional profile. The quality and Productivity of broccoli both are affected by heavy metal contamination, particularly cadmium (Cd). The current investigation focused on the potential role of silicon (Si) in alleviating Cd-induced stress in broccoli plants. A pot experiment was conducted under a completely randomized design with three Cd levels (0, 0.5, and 1 mM) and three Si concentrations (0, 1, and 2 mM). Morphological, physiological and anatomical traits were evaluated to assess plant responses to Cd stress and Si supplementation. Gas exchange traits, including photosynthetic rate, transpiration and stomatal conductance were estimated using an infrared gas analyzer (IRGA). Stress induced by Cd significantly reduced plant growth and physiological performance, whereas exogenous Si application notably improved plant tolerance. Application of Si improved photosynthetic activity (up to 3.24 μmol m^-2s^-1), plant height (44 cm), root length (20.63 cm) and shoot biomass compared with Cd-stressed plants without Si application. Additionally, Si application increased both fresh and dry biomass, indicating improved growth under Cd stress. Anatomical observations further revealed that Si supplementation mitigated Cd-induced cellular damage by maintaining better cellular organization and larger cell areas in root, stem, and leaf tissues, including the epidermis, cortex, phloem, and xylem. Overall, the results demonstrate that silicon plays a significant role in enhancing Cd stress tolerance in broccoli by improving morpho-physiological performance and cellular integrity. These findings suggest that Si supplementation could serve as an environmentally friendly strategy to reduce Cd toxicity and support sustainable crop production in contaminated soils.