Effect of salinity on growth, ion content and CO₂ assimilation rate in lemon varieties on different rootstocks

Abstract

Citrus rootstocks as well as lemon scions differ in their ability to restrict sodium and chloride ions and in their sensitivity to saline stress. To determine the behaviour of different rootstock‐scion combinations, 3 lemon cultivars on 3 different rootstocks were grown in containers in a greenhouse and irrigated with 5, 25 and 50 m M NaCl. Growth of the plants and foliar contents of sodium and chloride as well as physiological parameters including transpiration rate, gas exchange, stomatal conductance and chlorophyll content were evaluated. Shoot length of the plants on sour orange and on C. volkameriana showed a greater reduction with salinity than those on C. macrophylla . Accumulation of salt in the leaves was also scion dependent, cv. ‘Eureka’ having higher concentrations of sodium and chloride than the others. Assimilation rate of CO 2 and stomatal conductance were greatly reduced by salinity in the leaves of Verna and Eureka on sour orange. Gas exchange in the leaves was highly correlated with chloride and sodium contents in all lemon‐rootstock combinations. C. macrophylla showed a higher resistance to salinity than C. volkameriana and sour orange. Inferences on the mechanisms of action of salt on lemon trees are discussed.