EFFECT OF SALINITY ON GROWTH, ION CONTENT AND CO2 ASSIMILATION RATE IN LEMON VARIETIES ON DIFFERENT ROOTSTOCKS

Citrus rootstocks as well as lemon scions differ in their ability to r estrict sodium and chloride ions and in their sensitivity to saline st ress. To determine the behaviour of different rootstock-scion combinat ions, 3 lemon cultivars on 3 different rootstocks were grown in contai ners in a greenhouse and irrigated with 5, 25 and 50 mM NaCl Growth of the plants and foliar contents of sodium and chloride as well as phys iological parameters including transpiration rate, gas exchange, stoma tal conductance and chlorophyll content were evaluated. Shoot length o f the plants on sour orange and on C. volkameriana showed a greater re duction with salinity than those on C. macrophylla. Accumulation of sa lt in the leaves was also scion dependent, cv.'Eureka' having higher c oncentrations of sodium and chloride than the others. Assimilation rat e of CO2 and stomatal conductance were greatly reduced by salinity in the leaves of Verna and Eureka on sour orange. Gas exchange in the lea ves was highly correlated with chloride and sodium contents in all lem on-rootstock combinations. C. macrophylla showed a higher resistance t o salinity than C. volkameriana and sour orange. Inferences on the mec hanisms of action of salt on lemon trees are discussed.