| Scope and Method of Study. Aluminum toxicity in acidic soils is a common problem in bermudagrass areas across Oklahoma. Certain organic acids in root exudates can act as root zone chelators to reduce harmful effects when plants are under Al stress. Therefore, a growth unit study was developed to evaluate organic acid changes in 'Princess-77' bermudagrass root exudates. Bermudagrass was grown in sand profile treated with 100 ppm and 200 ppm of Al stress. Two control treatments with no Al at sand pH of 4.5 and 7.0 were also included. Each treatment was replicated three times in a randomized complete block design. The objectives of the study were to identify and quantify organic acids in bermudagrass root exudates affected by Al stress and the correlation between organic acid exudation and external Al concentration.;Findings and Conclusions: Al was accumulated in shoot tissues at concentrations of 1214.41 mg/kg and 2261.13 mg/kg dry wt. under 100 ppm and 200 ppm Al treatment respectively. There was a significant ( P = 0.01) negative linear relationship (r2 = 0.61) between Al leaf accumulation and bermudagrass root mass where root mass decreased significantly (P < 0.05) as Al accumulation increased. Citric, malic, oxalic and succinic acid were found in bermudagrass root exudates. Oxalic acid is the dominant acid accounts for 51-81 % of total organic acids and the exudation rate had a significant (P = 0.01) positive relationship (r2 = 0.78) with external Al concentrations. Citric acid was induced by Al stress and higher exudation rate was detected in 100 ppm Al stress, the average exudation rate of malic acid also increased under Al treatment comparing to control treatments. The results inidicate potential Al tolerance mechanisms presented in bermudagrass cultivar 'Princess-77'. |
