EFFECTS OF CARBON-DIOXIDE, WATER-SUPPLY, AND SEASONALITY ON TERPENE CONTENT AND EMISSION BY ROSMARINUS-OFFICINALIS

Rosmarinus officinalis L. plants were grown under carbon dioxide conce ntrations of 350 and 700 mu mol/mol (atmospheric CO2 and elevated CO2) and under two levels of irrigation (high water and low water) from Oc tober 1, 1994 to May 31, 1996. Elevated CO2 led to increasingly larger monthly growth rates than the atmospheric CO2 treatments. The increas e was 9.5% in spring 1995, 23% in summer 1995, and 53% in spring 1996 in the high-water treatments, whereas in low-water treatments the grow th response to elevated CO2 was constrained until the second year spri ng, when there was a 47%, increase. The terpene concentration was slig htly larger in the elevated CO2 treatments than in atmospheric CO2 tre atments and reached a maximum 37% difference in spring 1996. There was no significant effect of water treatment, likely as a result of a mil d low water treatment for a Mediterranean plant. Terpene concentration increased throughout the period of study, indicating possible age eff ects. The most abundant terpenes were alpha-pinene, cineole, camphor, borneol, and verbenone, which represented about 75% of the total. No s ignificant differences were found in the terpene composition of the pl ants in the different treatments or seasons. The emission of volatile terpenes was much larger in spring (about 75 mu g/dry wt/hr) than in a utumn (about 10 mu g/dry wt/hr), partly because of higher temperature and partly because of seasonal effect, but no significant difference w as found because of CO2 or water treatment. The main terpene emitted w as alpha-pinene, which represented about 50% of the total. There was n o clear correlation between content and emission, either quantitativel y or qualitatively. More volatile terpenes were proportionally more im portant in the total emission than in total content and in autumn than in spring.