Abstract.Water uptake is required when plants enlarge but growth may also occur when no external water is present. To determine whether this growth also depends on water, we studied etiolated seedlings of soybean (Glycine maxL. Merr.) deprived of external water by transplanting to vermiculite of low water content or by transferring to water‐saturated air. When the external water supply was decreased or removed, the roots continued to grow rapidly but the stems abruptly decreased in growth (in 1 min) and continued to grow slowly. The stem tissues gained water content in the upper elongating region and lost water content in the basal region. Removal of the basal stem caused growth to slow further. When all tissues surrounding the stem elongating region were removed simultaneously, stem growth decreased abruptly to near zero. Control experiments showed that the decreased growth was not caused by wounding or the removal of the auxin or nutrient supply. It is concluded that growth always depended on a source of water and, when external supplies were absent, internal water was mobilized to enlarging tissues of shoots and roots mostly from the basal stem tissues in these seedling