Aluminum and water stress effects on growth and proline of sorghum

Plants grown on acid soil with high exchangeable Al often show decreased growth and water deficit (WD) symptoms. Detailed comparisons of separate and combined effects between Al toxicity and WD would help identify plants for tolerance or resistance to these factors to enhance plant improvement procedures. Separate and simultaneous effects of Al toxicity and WD [induced by polyethylene glycol-8000 (PEG)] on growth and proline accumulation of two sorghum (Sorghum bicolor L. Moench) genotypes were determined. [Redlan] (drought- and Al-sensitive) and SC283 (drought- and Al-resistant) sorghum were grown in a growth chamber in nutrient solutions with 0, 200, 400, and 600 mu mol/L Al and 0, 4.4, 7.0, and 3.6% PEG separately and in combination. Increased Al and WD separately decreased shoot and root dry matter, leaf area, net main axis root length, total and specific root length, (RL/root DM). The WD treatments had greater effects on growth traits than Al. Combinations of Al and PEG (Al+PEG) decreased shoot and root DM, LA, NMARL, and TRL. The WRL increased as Al increased, and LA/root DM and LA/RL were not affected by Al+PEG. Proline did not increase in shoots and roots of plants grown with Al, but did increase extensively when grown with WD; sheets had higher proline than roots. Combinations of Al+PEG resulted in higher proline in both shoots and roots than Al stress alone. Overall, SC283 was generally less affected by Al and WD than Redlan.