Effect of Al in soil on photosynthesis and related morphological and physiological characteristics of two soybean genotypes

Ecological impact assessments of contaminated soil on plants has been an interesting area in the last few years as restoration of contaminated environments for better ecological health is addressed. In this study, the photosynthetic and related morphological and physiological characteristics of two soybean (Glycine max Merrill.) varieties were evaluated in response to aluminum (Al) stress in soil. The pot-grown soybean plants were cultured with different supplemental aluminum, and measurements was conducted during the 5-foliate period. Results indicate that Al at low concentrations in the soil is helpful to growth, and Al is toxic to plants only when the concentration exceeds a certain threshold. Increased leaf area, root surface area, specific leaf weight (SLW), and lower malondialdehyde levels were found in soybean plants under a 200 mg/kg Al treatment. However, higher aluminum concentrations (800 mg/kg) caused declining chlorophyll contents, depressed photosynthesis rates (PN), enhanced transpiration rates, and decreased PAR utilization efficiency (PUE) and water utilization efficiency. No significant difference in stomatal conductance or leaf water potential was observed among soybean plants under the various aluminum treatments. Moreover, higher aluminum concentration significantly increased lipid peroxidation, decreased cell membrane stability, and changed the activities of superoxide dismutase (SOD) in the leaves of both plants. It is concluded that soybean plants maintain relatively higher SLW, PN, PUE, WUE, SOD activity to cope with high aluminum stress. Our study produces insights into plant behavior under contamination stress, which may be useful in the selection and breeding of aluminum-tolerant soybean cultivars for the sustainable development of agriculture and ecology.