The Extent and Pattern of Osmotic Adjustment in White Clover (Trifolium repens L.) During the Development of Water Stress

White clover plants were subjected to water stress following the cessation of watering. As a water deficit developed, water and osmotic potentials were measured in stolon tips, leaves from the stolon tip and leaves from the plant crown. Pressure potentials were calculated. Pressure potential was maintained in stolon tips even when water potential fell to around −2·0 MPa. In contrast, pressure potential in leaves fell rapidly as water stress developed. Total amino acid and potassium levels were largely unaffected in both stolon tips and leaves. Water-soluble carbohydrates and proline accumulated during water stress. The increase in proline level in leaves did not follow the same pattern as that in stolon tips, although toward the end of the water stress period the level had increased by a similar extent in both parts of the plant. Additionally, pressure potential and osmotic potential appeared to be significantly related to proline content in stolon tips. No such relationship was found for leaves. The role of proline in osmotic adjustment is discussed.