Sorbitol Accumulation in Plantaginaceae; Further Evidence for a Function in Stress Tolerance

Abstract

Summary The well known potential of Plantago maritima to accumulate the polyhydric alcohol sorbitol was compared with that of two other species of Plantago collected in various environments: P. coronopus and P. lanceolata P. maritima is, by far, the most effective, the sorbitol content reaching values as high as 8.9% of the dry matter in the shoots. However, significant amount of sorbitol were also found either in the roots and the shoots of P. coronopus growing in coastal habitats (resp. 6.2 and 5.8% of dry matter) or in the shoots of P. lanceolata growing in a dry habitat (6.2% of dry matter). Comparative analyses on various batches of P. maritima gave further evidence for an adaptive function of sorbitol in salt resistance. In the two other species, the level of sorbitol detected could also be partly related to some kind of stress response since, after transfer from field conditions to a Hoagland half strength medium, the sorbitol level dramatically decreased while the water content of the tissue rose. On the other hand, when plants were transferred to a medium containing NaCl (200 mM) the sorbitol level decreased or increased according to the severity of stress produced with this salt concentration as compared to that occurring under field conditions.