Changed composition of metabolites in Solanum tuberosum subjected to osmotic stress in vitro: Is sorbitol taken up?

Climate change and the increasing world population will lead to an increased water shortage. This gives rise to the need for plant cultivars which are drought tolerant. Solanum tuberosum L. is important not only as a nutritive rich food, but starch potatoes are of great value for the industry. Two starch genotypes of S. tuberosum L. divergently responding to osmotic stress were subjected to medium containing 0.2 M sorbitol in vitro. A targeted metabolomics approach was performed in which 42 metabolites were analysed 11 days after the transfer of the plants to the experimental medium. The sensitive genotype displayed stress responses comprising higher abundant metabolites such as phenylalanine, proline and sucrose and a decrease e.g. in GABA and fumaric acid. These can be used for protein build up, nitrogen storage and the protection through osmotic active compounds. In contrast, the tolerant genotype showed a higher abundance in compounds used as osmolytes (citric acid and proline), which might give rise to acclimatisation to the stress. Interestingly, in chromatograms of both genotypes a high sorbitol peak was detected, whereas control plants or plants treated with 4.8 % PEG 8000 did not accumulate this substance. Conclusively, sorbitol is taken up during in vitro growth, which raises the question for the fate and effect of the incorporated sorbitol.