GROWTH, ION CONTENT AND PHOTOSYNTHETIC PERFORMANCE OF SALT-STRESSED KIWIFRUIT PLANTS

Rooted cuttings of kiwifruit (Actinidia sinensis P. cv Hayward) were g rown in sand-perlite mixture (1:3), and irrigated with half-strength, recycled Hoagland nutrient solution, containing 0, 5, 10, 15, 20 and 3 0 mM of added NaCl. Growth, ion content and gas exchange response to s alt treatment were examined over 60 days. Salinity led to reduced grow th, although foliar symptoms of salt toxicity were absent. Plant dry w eight and leaf area were reduced significantly with 10 mM NaCl in nutr ient solution. Leaf expansion rate, leaf size and number of leaves per plant were affected by NaCl salinity. Sodium accumulated mainly in ro ots while chloride content in leaves and roots increased significantly above 10 mM NaCl. Photosynthetic rate (Pn) decreased with increased l evels of leaf chloride. The decrease in photosynthesis was only partia lly due to stomatal closure. There was no reduction in intercellular C O, concentration (Ci) for salt-stressed leaves indicating that nonstom atal factors were contributing to the decrease of Pn. In conclusion th e data indicate that kiwifruit is a salt sensitive plant and salinity affects its growth through reduction in leaf area development and decl ine in photosynthetic capacity.