ALUMINUM AND WATER-STRESS EFFECTS ON GROWTH AND PROLINE OF SORGHUM

Plants grown on acid soil with high exchangeable Al often show decreas ed growth and water deficit (WD) symptoms. Detailed comparisons of sep arate and combined effects between Al toxicity and WD would help ident ify plants for tolerance or resistance to these factors to enhance pla nt improvement procedures. Separate and simultaneous effects of Al tox icity and WD [induced by polyethylene glycol-8000 (PEG)] on growth and proline accumulation of two sorghum (Sorghum bicolor L. Moench) genot ypes were determined. [Redlan] (drought- and Al-sensitive) and SC283 ( drought- and Al-resistant) sorghum were grown in a growth chamber in n utrient 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 sep arately decreased shoot and root dry matter, leaf area, net main axis root length, total and specific root length, (RL/root DM). The WD trea tments had greater effects on growth traits than Al. Combinations of A l and PEG (Al+PEG) decreased shoot and root DM, LA, NMARL, and TRL. Th e WRL increased as Al increased, and LA/root DM and LA/RL were not aff ected by Al+PEG. Proline did not increase in shoots and roots of plant s grown with Al, but did increase extensively when grown with WD; shee ts had higher proline than roots. Combinations of Al+PEG resulted in h igher proline in both shoots and roots than Al stress alone. Overall, SC283 was generally less affected by Al and WD than Redlan.