Drought-induced metabolic adjustments in woodland strawberry leaves: the role of soluble carbohydrates and starch

Water deficit is one of the most important abiotic factors limiting crop yields. To better understand the link between carbohydrate balance and drought stress response in strawberry plants (Fragaria vesca), we monitored by liquid chromatography the carbohydrate status in leaves during exposure to drought of different duration and intensity as well as subsequent recovery. In two greenhouse experiments that differed in the rate of reaching the target water deficit, strawberry leaves showed osmotic adjustment, with gradual increases in glucose and fructose content, likely provided by observed starch degradation. At the point of the most severe stress, proline content increased, while stress markers, such as malondialdehyde content and chlorophyll fluorescence, showed no significant changes. It indicates the defence mechanisms' ability to protect cellular structures effectively. Strawberry, a member of the Rosaceae family, motivated us to investigate the role of sorbitol in the stress response. However, we found no sorbitol in any stress or control situations. Finally, testing sorbitol's ability to support strawberry plant or non-green callus growth in vitro did not indicate that sorbitol could be used as a carbon and energy source. In conclusion, strawberries exhibit marked changes in soluble carbohydrate and starch content as an efficient defence against drought, without apparent involvement of sorbitol.