Low molecular weight organic acids and fatty acids in root exudates of twoLupinus cultivars at flowering and fruiting stages

Low molecular weight organic acids (LOAs) and fatty acids in root exudates of two lupin cultivars, Lupinus albus cv. Multolupa and L. luteus cv. Tremo silla, were determined at flowering and fruiting stages. LOAs were analysed by capillary electrophoresis. Acetic and citric acids were the most abunda nt, especially the latter in L. luteus at the flowering stage (5922.79 mug/ g dry root). The significant decrease in acid content of both cultivars fro m flowering to fruiting stages was also striking. The highest levels of ace tic acid were detected in L. luteus at fruiting stage (1542.03 mug/g dry ro ot). The significant citrate production in L. luteus could be related to th e low phosphorus concentration in the studied soils but not to proteoid roo ts, which were detected only in L albus. The source of the LOAs detected in these exudates is also discussed, since they may be produced either by the plant or by the associated rhizobacteria. The profile of phospholipid fatt y acids was determined by high-resolution GC. A high level of 18:2 omega6 ( a fatty acid specific to fungi) was found in exudates of L. luteus (a mycor rhizal plant) in contrast to L. albus (a non-mycorrhizal plant). Copyright (C) 2001 John Wiley & Sons, Ltd.