SEEDLING EMERGENCE, GROWTH, AND MINERAL CONCENTRATION OF 3 CITRUS ROOTSTOCKS UNDER SALT STRESS

Salt tolerance of Carrizo citrange (CC), sour orange (SO), and Cleopatra mandarin (CM) rootstocks during emergence and early seedling stage of development was studied under greenhouse conditions. Increasing salt concentration in the nutrient solution delayed and depressed seedling emergence (SE), increased time to 50% emergence, reduced seedling growth (SD) but did not affect emergence spread. At the first salinity level (5 mmol), emergence of the first seedling (EFS) was delayed by 2-3 days in CC and one day in SO but was not affected in CM. At the two lowest salinity levels (5 and 10 mmol), final percent emergence (FPE) was not affected in CC but was reduced in SO and CM while shoot biomass was reduced in CC but was not affected in SO and CM. This study showed a non-consistent trend among citrus rootstocks concerning whether the delay in emergence is more sensitive to salt stress than final percent emergence. However, SG was generally more affected by salinity than SE, particularly at high salinity levels. Shoot and root N and Cl concentrations generally increased with increasing salt concentrations. Shoot Cl concentration was found to be a better tool than root Cl concentration in evaluating die extent of the injurious effect of salt stress and a better parameter in ranking salt tolerance of citrus rootstocks. This study also showed that salt tolerance is not a constant character in citrus rootstocks but varies with the stage of seedling development.