Sorbitol accumulates in plants under water stress because less sorbitol is transported out of the leaves. When 14 C-sucrose was introduced to apple shoots, it was broken down into sorbitol in non-stressed leaves. Water stress reduced the conversion of glucose to sorbitol, but sorbitol levels increased in mature leaves over time. Young leaves and stems had less sorbitol under water stress. This shows that sorbitol accumulation in plants during water stress is caused by reduced sorbitol transport.