Role of K⁺ and Cl^- in osmotic adjustment in roots and hypocotyls of intact mung bean seedlings

It was confirmed that osmotic adjustment occurred in young intact mung bean (Vigna mungo (L.) Hepper) seedlings exposed to high osmotic pressure stress. Root growth was not affected by osmotic pressure of less than 200 mOsra in the external solution, although hypocotyl growth was conspicuously reduced. Under this moderate osmotic stress, intracellular K⁺ concentration, [K⁺]_i, increased dramatically during the osmotic adjustment in all the regions of the root, but the intracellular Cl^- concentration, [Cl^-]_i, increased only in the aged mature region of the root (28-33 mm from the root tip). About a half of the intracellular osmotic pressure in the aged mature region of the root could be ascribed to the contributions of [K⁺]_i and [Cl^-]_i, but in the hypocotyl, [K⁺]_i only contributed slightly to the osmotic adjustment.