Combined Effects of Elevated Carbon Dioxide and Aluminum Toxicity on Maize ( Zea mays L.)

The individual effects of elevated carbon dioxide (eCO ₂ ) and soil acidity on maize ( Zea mays L.) growth and development are well documented, although little is known about their interactive effects. This study investigated the combined effects of eCO ₂ with aluminum (Al) toxicity on the growth of six quality protein maize (QPM) inbred lines under controlled growth chambers. The treatments (CO ₂ , Al toxicity, and genotype) were arranged in a 2 × 2 × 6 factorial randomized complete block design, replicated three times, and run twice for validation purposes. Carbon dioxide treatments were 400 and 600 mol ⁻¹ under ambient and elevated conditions, respectively. Acidic soils (4.5 pH) were incubated with Al ₂ [SO4] ₃ at a rate of 24 mg kg ⁻¹ of soil to expose plants to Al toxicity, but no Al ₂ [SO4] ₃ incubation was performed under control conditions. Elevated CO ₂ (600 mol ⁻¹ ) significantly alleviated the undesirable effects of Al stress ( p < 0.001) on the growth and development of some QPM genotypes. The interactions caused significant improvements in plant height, stem diameter, root, and total biomass relative to the control. Based on the total stress resistance index (TSRI), IBL 4 was classified as tolerant to eCO ₂ × Al toxicity. However, some genotypes that were previously classified as Al‐tolerant could not uphold their tolerance due to eCO ₂ × Al toxicity interactive effects. Hence, there is a need for continued investigations into the effects of different abiotic factor combinations that are anticipated in the future.