Aquaporins in the plasma membrane of leaf callus protoplasts of Actinidia deliciosa var. deliciosa cv. Hayward

Abstract

The water transport activity of Actinidia deliciosa protoplasts was determined using a cell imaging system. Results showed that the protoplast volume increased swiftly when placed in a hypoton-ic medium, and also increased with an increase in medium osmotic gradients. The osmotic water permeability coefficient (P_f) values were 0.118 × 10^–3, 0.121 × 10^–3, and 0.133 × 10^–3 cm s^–1 when the osmotic gradients were 75, 100, and 125 mosmol, respectively. The water transport activity of protoplas-ts could be inhibited by HgCl₂ and stimulated by amphotericin B. Moreover, ZnCl₂ and ZnSO₄ had a significant inhibitory effect on the water transport activity of the protoplasts. Our results indicate that the Actinidia deliciosa protoplasts had properties typical of aquaporins, suggesting that aquaporins were present at the plasma membrane.