Alteration in growth, leaf gas exchange, and photosynthetic pigments of maize plants under combined cadmium and arsenic stress

Increasing soil contamination by heavy metals is a major threat to environmental safety and global food security. The present study examined the influence of Cd and As stresses on morpho-physiological growth and yield of two contrasting maize cultivars (Run Nong 35 and Dong Dan 80). The Cd (100 μM) and As (200 μM) were applied individually as well as in combination (Cd + As) at 30 DAS. A control without Cd or As stress was also maintained for comparison. Application of Cd and As alone or in combination substantially reduced the growth (plant height, number of leaves per plant, leaf area, stem diameter, and shoot fresh and dry weight) and yield (number of ears per plant, number of kernels per ear, and 100-kernel weight) contributing traits in both maize cultivars particularly in Run Nong 35. Furthermore, pronounced reductions in gas exchange attributes (photosynthesis, stomatal conductance, transpiration rate, and intercellular CO₂) and chlorophyll contents were observed in metal-stressed plants. The combined application of Cd and As was more detrimental for maize, and this treatment recorded the maximum reductions in morpho-physiological growth and yield of both cultivars. Cultivar variations were also apparent, and Dong Dan 80 performed better than Run Nong 35 for all the studied attributes. The higher tolerance of Dong Dan 80 was associated with better leaf gas exchange and maintenance of chlorophyll contents in this cultivar under Cd and As stress.