CONCERNING THE FUNCTION OF RUBBER HYDROCARBON (CAOUTCHOUC) IN THE GUAYULE PLANT, PARTHENIUM ARGENTATUM A. GRAY

Abstract

LLOYD (11,12), who originally believed that rubber hydrocarbon (caoutchouc) in the guayule plant occurred in the parenchymatous cells as solid particles, stated that "rubber appears to have no physiological function in the guayule plant"; but this viewpoint was questioned by SPENCE (21) on the basis of work with oxydases in Hevea latex. Later LLOYD (13) demonstrated that the rubber in the parenchymatous cells of guayule "occurs as a colloidal suspension, precisely as in the latex of Hevea," and this led him to modify his viewpoint for he realized the possibility that rubber in colloidal suspension could be attacked by enzymes. In support of this hypothesis could be cited the work of FAIVRE (2, 3, 4), with Tragopogon porrifolius, Morus alba, and a Ficus sp., who varied the conditions, including absence of carbon dioxide, under which they were grown, and observed impoverishment of the latex; and the experiment of SPENCE (21) who reports that young Ficus elastica "grown in an atmosphere and soil free of carbon dioxide, gradually drew on their milk which became nothing more than water after a few weeks' time." However, LLOYD (13) insisted that proof was required for the hypothesis that the rubber hydrocarbon in guayule is actually a reserve substance and is made use of in metabolism.The results of SPENCE and MCCALLUM (22) showed a loss in grams of rubber per plant during conditions that favored utilization of carbohydrate reserves. However, observations during the course of experiments from 1942 to 1944 showed no such loss of rubber occurring in guayule plants under similar conditions. It was thought possible because of the great variability of seedling guayule plants that the results of SPENCE and MCCALLUM (22) may have been vitiated by failure to adequately replicate the treatments in order to eliminate the possibility of the differences being nothing more than chance variation. Since this subject is very important not only from the theoretical standpoint of plant physiology but also in connection with guayule rubber production, the work here reported was undertaken to test the conclusions of previous workers. MethodsGuayule nursery seedlings were grown in gravel culture in the greenhouse under three levels of carbon assimilation: Treatment I. No leaves removed.

Water stress and seasonal effects on rubber quality in irrigated guayule

“…Guayule has been reported incapable of using stored rubber as a food reserve (Traub, 1946;Benedict, 1949). In our study, rubber accumulation continued through April, followed by a loss in yield in June (Table I).…”

Levulins and Inulin in Guayule, Parthenium argentatum A. Gray

“…The corresponding values for 1% HCl are slightly higher than those indicated for top invertase. It may be of interest to note that ADAMS, RICHTMYER and HUDSON (1) report that the pH conditions for the maximum hydrolysis of sucrose, raffinose and inulin differ, and conclude that a specific injilase -rather than a ,3-D-fructofuranosidase is responsible for inulin hydrolysis (3,5,6,7,38,39,40). The making of such measurements has proved to be a more dynamic, and therefore a more valuable tool in physiological research than the analysis of total cold water soluble polysaccharides alone.…”