EFFECTS OF SALINITY ON SOME CITRUS SCION-ROOTSTOCK COMBINATIONS

Chloride and sodium concentrations, water relations and gas exchange p arameters were measured on leaves of Clementine (Citrus Clementine Hor t. ex. Tan) and Navel orange [C. sinensis (L.) Osb] scions grafted on Cleopatra mandarin (C. reticulata Blanco) and Troyer citrange (C, sine nsis x Poncirus trifoliata) rootstocks grown at increasing levels of N aCl in the external medium. Other parameters affected by salinity such as growth and defoliation were also recorded. Scions on Cleopatra man darin accumulated less Cl- in their leaves than did scions on Troyer c itrange. Also, leaf Cl- levels in Clementine scions were lower than in Navel orange when both were grafted on the same rootstock. However, s odium concentration was lower in scions on Troyer citrange than in Cle opatra mandarin. Leaf water potential, stomatal conductance, photosynt hesis and growth were reduced more in grafted plants of salt-treated N avel orange than those of sail-treated Clementine. However, choice of rootstock had little effect on salt-induced changes in these parameter s. 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 g rowth at increasing salinity levels depended more on the scion type th an on Cl- or Na+ concentration in leaves. Otherwise, leaf injury and d efoliation were closely correlated with leaf Cl- concentration. (C) 19 95 Annals of Botany Company