INORGANIC COMPOSITION OF EXUDATE FROM EUREKA LEMONS TREATED WITH ELEMENTAL SULFUR DUST

Abstract

IN STUDIES ON the physiological effects of elemental sulfur dust on citrus fruits (Turrell, 1950), it was noted that at temperatures of 105?-140?F. both nondusted and sulfur-dusted lemons contained in pyrex bottles through which a stream of washed air was passed yielded a yellow liquid. Because of the experimental conditions imposed on the fruit, the liquid might be considered a condensate, but it was observed in these studies, as in early stages of sulfur burn, that the affected area usually developed a translucent appearance. This has been interpreted as indicating an exudation (leakage sap) of the cell solution into the intercellular spaces of the mesocarp, a condition likewise developing when citrus fruits are incubated in closed systems. Perhaps the yellow liquid thus formed mav be correctly described as both a condensate and an exudate: the first because the containers were visibly covered with droplets of moisture, and the second because of the large number of nonvolatile constituents found in the qualitative analysis (Turrell, 1950) and the translucent appearance of the fruit peel. The term exudate is preferred, however, and is used throughout this report. The condensate is considered as an unavoidable contaminant. Exudation, apart from dew formation, has not been observed generally in citrus under field conditions in California. Deposits have been observed on foliage leaves of citrus in Texas, however, by Ivanoff (1941). This finding suggests that exudation or guttation in citrus may occur under natural growing conditions. The organic and inorganic constituents in exudates of nondusted and sulfur-dusted lemons are of interest because they may be indicative of the effects of elemental sulfur dust as compared with those of heat. Since no qualitative differences have been found in the exudates of such fruit, but a difference in specific gravity has been observed (Turrell, 1950), a quantitative study of the inorganic and organic composition of exudates from intact Eureka lemons was undertaken. The present report concerns the inorganic constituents. REVIEW OF LITERATURE. Numerous chemical analyses of exudation or guttation fluids of intact plants have been made. De Saussure (1804) appears to have been one of the first to analyze the deposit left by the exudates evaporated from leaf surfaces. At the time of his study the injury caused by or associated with the incrustation left by evap-