Seasonal changes in rubber and resin contents in Chrysothamnus nauseosus ssp. hololeucus and ssp. turbinatus
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Chrysothamnus nauseous (rubber rabbitbrush) is a desert shrub that grows in high density in large populations over a wide range of environmental conditions in the western United States and contains natural rubber that has potential commercial value. Individual plants of two sympatric subspecies (turbinatus and hololeucus) were analyzed to determine the distribution of rubber and resin within the plant. The highest rubber and the lowest resin contents were in the stems near the soil level whereas the highest resin and lowest rubber were in the top of the plants. Negative correlation between rubber and resin from top to bottom of the plants was significant (r2 = -064, p = 003) for ssp. turbinatus. During the growing season, the highest rubber and lowest resin contents occured during the summer for both subspecies. In contrast the highest resin and lowest rubber contents occured in the spring for both subspecies. Negative correlation between rubber and resin for one year old tissue in ssp. turbinatus was very significant (r2 = -076, p = 0004). Rubber content was highest when soil moisture was lowest and temperatures were highest. Results suggest that rubber and resin contents are under environmental regulation and that it may be possible to influence rubber and resin content in rubber rabbitbrush by using stress treatments. 1988.
