Effects of Salinity on Some Citrus Scion-Rootstock Combinations

Chloride and sodium concentrations, water relations and gasexchange parameters were measured on leaves of Clementine (CitrusClementine Hort. ex. Tan) and Navel orange C. sinensis (L.)Osb] scions grafted on Cleopatra mandarin (C. reticulata Blanco)and Troyer citrange (C. sinensis x Poncirus trifoliata) rootstocksgrown at increasing levels of NaCl in the external medium. Otherparameters affected by salinity such as growth and defoliationwere also recorded. Scions on Cleopatra mandarin accumulated less Cl^- in their leavesthan did scions on Troyer citrange. Also, leaf Cl^- levels inClementine scions were lower than in Navel orange when bothwere grafted on the same rootstock. However, sodium concentrationwas lower in scions on Troyer citrange than in Cleopatra mandarin. Leaf water potential, stomatal conductance, photosynthesis andgrowth were reduced more in grafted plants of salt-treated Navelorange than those of salt-treated Clementine. However, choiceof rootstock had little effect on salt-induced changes in theseparameters. For each scion, reduction in leaf stomatal conductancewas closely correlated with decrease in leaf water potential.Also, a significant correlation between photosynthesis and stomatalconductance was found. The results indicate that reductions in gas exchange parametersand growth at increasing salinity levels depended more on thescion type than on Cl^- or Na⁺ concentration in leaves. Otherwise,leaf injury and defoliation were closely correlated with leafCl^- concentration.Copyright 1995, 1999 Academic Press Citrus, photosynthesis, salinity, water relations