EFFECTS OF SALINITY ON SOME CITRUS SCION-ROOTSTOCK COMBINATIONS

Chloride and sodium concentrations, water relations and gas exchange parameters were measured on leaves of Clementine (Citrus Clementine 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) rootstocks grown at increasing levels of NaCl in the external medium. Other parameters affected by salinity such as growth and defoliation were also recorded. Scions on Cleopatra mandarin accumulated less Cl- in their leaves than did scions on Troyer citrange. Also, leaf Cl- levels in Clementine scions were lower than in Navel orange when both were grafted on the same rootstock. However, sodium concentration was lower in scions on Troyer citrange than in Cleopatra mandarin. Leaf water potential, stomatal conductance, photosynthesis and growth were reduced more in grafted plants of salt-treated Navel orange than those of sail-treated Clementine. However, choice of rootstock had little effect on salt-induced changes in these parameters. For each scion, reduction in leaf stomatal conductance was closely correlated with decrease in leaf water potential. Also, a significant correlation between photosynthesis and stomatal conductance was found. The results indicate that reductions in gas exchange parameters and growth at increasing salinity levels depended more on the scion type than on Cl- or Na+ concentration in leaves. Otherwise, leaf injury and defoliation were closely correlated with leaf Cl- concentration. (C) 1995 Annals of Botany Company