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

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Abstract
An expt. was conducted to determine the effect of carbon assimilation levels, ranging from very low to the normal, on the utilization of reserve foods in the guayule plant. Plants grown under a very low level of C assimilation by repeated removal of new top growth, (a) depleted their reserves of free sugars, levulins and inulin, almost to 0; (b) utilized part of the pento-sans; (c) lost no rubber hydrocarbon (caoutchouc), but showed a significant increase which was associated with a corresponding decrease in the resins fraction (a mixture), and (d) in the stems, lost a greater amt. in dry wt. than could be accounted for on the basis of loss in the water-soluble carbohydrates and pentosans detd. The data (a) show that the rubber hydrocarbon (caoutchouc) in the guayule plant apparently does not function as a food reserve, and (b) suggest that the resins fraction (a mixture) may contain a rubber precursor, and (c) that other reserves, such as pectins, might possibly be important food reserves and deserve greater attention in physiol. research.