The influence of aluminum on growth, carbohydrate, and organic acid content of an aluminum-tolerant and an aluminun-sensitive cultivar of wheat

Abstract

An aluminum-sensitive cultivar (Katepwa) and an aluminum-tolerant experimental line (PT741) of Triticum aestivum were grown in nutrient solutions containing 0–400 μM aluminum at pH 4.5. After 18 days of growth, plant fresh weight was reduced in the Al-sensitive and Al-tolerant germ plasm by as little as 100 and 200 μM Al, respectively, and a number of changes in carbon allocation were observed. Shoot to root ratios increased with Al concentration in the Al-sensitive 'Katepwa' and remained constant in the Al-tolerant PT741.In both 'Katepwa' and PT741, shoot carbon was increasingly deposited into starch and fructan pools with increasing Al concentration. However, fructan deposition was more marked in the Al-sensitive 'Katepwa', possibly reflecting a failure to export carbon to the roots. Differences between Al-tolerant and Al-sensitive germ plasm were also observed in some organic acid levels. Contrary to several previous reports, higher concentrations of organic acids were found in the roots of Al-sensitive 'Katepwa'. In shoots, higher concentrations of organic acid were found in the Al-tolerant PT741. These results suggest that allocation of carbon to specific pools is affected by the concentration of Al. However, synthesis of organic acids and subsequent chelation of intracellular Al does not appear to represent a tolerance strategy in wheat. Observed changes in metabolic levels more likely represent a broad array of toxic lesions, with the magnitude of changes being greater in the Al-sensitive 'Katepwa' than in the Al-tolerant PT741. Key words: stress, aluminum tolerance, aluminum sensitivity, fructans.