Seasonal Effects on Guayule Resin Composition

Rubber and resin levels in guayule line N396 were monitored on a whole-shrub basis from January through July 1984. This sample interval included the period of cold-weather stress associated with rubber formation and the period of renewed vegetative growth. Monthly levels were also determined for selected resin components. Fatty acid triglycerides were most abundant (>8000 ppm) in January, with lower levels (2300–4400 ppm) in succeeding months. Triterpenoid levels showed relatively little variation (1700–2500 ppm for argentatin A). Sesquiterpene esters were most abundant in March (3600 ppm for guayulin A) and July (2900 ppm) and least abundant in April and May (<50 ppm). These variations have direct implications for shrub processing and byproduct applications.