Estimation of the Osmotic Potential of Citrus Seedling Leaf Sap at Different Soil-Moisture Levels by Means of Refractometry and Conductimetry1

The refractive index and electrical conductivity of the leafsap of two citrus species, sour orange and sweet lime, weremeasured at different soil-moisture levels. Their osmotic potentialscontributed by electrolytes and soluble metabolites were estimated.The sum of these two estimates agreed fairly well with the totalosmotic potential of the leaf sap as measured by cryoscopy.The results indicate that the refractometry-conductimetry methodis adequate for studying the changes of osmotic potential ofcitrus seedlings during the course of irrigation cycles.     

Beta-ray Gauging Technique for Measuring Leaf Water Content Changes of Citrus Seedlings as Affected by the Moisture Status in the Soil

The beta-ray gauging technique was used to measure the relativechanges occurring in the water content of sour orange and sweetlime leaves as a result of soil wetting and drying cycles. Promethium-147served as the radiation source and was found suitable for measuringchanges in citrus leaf thickness within the range of 20 mg/cm²(when soil moisture content was at ‘pot capacity’)to 10 mg/cm² (when soil moisture dropped to wilting point).By using the correlation between beta-ray gauging measurements,leaf thickness, and relative turgidity, it is possible to determinethe status of water in citrus leaves under different soil moistureconditions.