Over the past few years recognition of the ecological importance of terpenoids has increased enormously. These compounds are the largest group of plant chemicals and terpenoid biosynthesis provides more opportunities to generate new products than other pathways do. Numerous examples have revealed that terpenoids have multiple effects, which contribute to community/ecosystems properties.
In July 1998, the 1st Workshop of the Italian Group of Terpenoid Researchers in the National Research Council of Rome (CNR) was convened to discuss the ecological functions of plant terpenoids as well as their commercial applications. Francesco Loreto (CNR-Rome) chaired the meeting. The opening lecture by Marco Michelozzi (CNR-Firenze) was appropriately devoted to briefly reviewing recent aspects of the multiple ecological roles of terpenoids. Plant terpenoids serve primarily as defence against insects and diseases as well as elicitors of antifeeding reactions in some vertebrates. These substances attract insect pollinators and they are implicated in pheromonal communication and in allelopathic interactions. Monoterpenes also play a role in indirect plant defence at third-trophic-level interactions. The considerable variability in mixtures of terpenes has been shown to be under strong genetic control and such finding permits the use of terpenoids as biochemical markers to identify superior trees.
Furthermore, volatile terpenes emitted from plants partecipate in atmospheric chemistry. The global emission of both isoprene and monoterpenes is estimated to be about the same as the total global methane emission. Lower terpenoids can react with unstable reactive gases and may act as precursors of photochemical smog therefore indirectly influencing community and ecosystem properties.
Paolo Ciccioli (CNR-Rome) presented a highly informative talk on the contribution of terpenoid emission to ozone production and the different techniques to quantify the biogenic emissions (bag enclosure and relaxed-eddy accumulation). Olav Csiky (European Commission, Envinronment Institute-Ispra) spoke on seasonal fluctuations of the emission factors and variability in terpenoid emissions among different Mediterranean oaks. Knowledge about the response of the emission to environmental factors is indispensable to elaborate models for forest canopy terpenoid emissions. Sebastiano Delfine (University of Molise) and Francesco Loreto presented current progress in physiological studies on the emission and on the role of isoprenoids in response to abiotic stresses. Experiments have shown the dependence of terpene emission on light, CO2 and O2 concentrations and have indicated that isoprenoids emitted from plants without storage structures are made from recently fixed carbon. Terpene emission is temperature-dependent and thermal tolerance have been observed by fumigating the leaves with isoprene and monoterpenes. Terpene synthesis might represent a protective system for phosynthetic membranes and may have been evolved by plants to counteract environmental stresses. Isoprenoids may serve also as protective compounds against oxidative agents since terpenoids can remove radicals. However, although many progress has been made in understanding terpene emissions, much more remains to be learned.
Knowledge of the ecological roles of terpenes is of fundamental importance for the ecology and management of forest as well as for commercial applications in agroindustry and other related natural products industries. In recent years recognition is increasing about the use of terpenoids as the basis for production of biodegradable natural pest control agents and herbicides. Growing awareness of the public health consequences of synthetic food additives has stimulated interest in the search for natural healthy safe products and terpenoids have great potential as a source of food aromas and preservatives. Enrico Casadei (FAO) gave an overview of international regulations for natural products used as food additives. He explained that the division between natural and synthetic food additive can not be considered as separated by a net mark; moreover, “Specifications of Identity of Purity” for natural products are not easily established since environmental factors can affect the chemical composition of the product.
Franco Vincieri, the president of the Phytochemical Society of Italy, gave an interesting talk on pharmacological properties of terpenoids. Since ancient times great attention has been directed to the use of terpenoids as therapeutic agents. Terpenoids are employed as anti-inflammatories, decongestants for the respiratory tract, sedatives, carminatives, cardiotonic agents and anti-cancer compounds as taxol, a diterpenoid from Taxus brevifolia. In addition, terpenoids provide enormous value in cosmetics and in making perfumes.
The plenary session was followed by talks from voluntary speakers. Various topics were presented. Rita Baraldi (CNR-Bologna) talked about variability in biogenic emissions from different fruit trees during blossoming. Carlo Calfapietra and Paolo de Angelis (University of Viterbo) presented preliminary results on biogenic emission from plants of Quercus ilex growing in high CO2 environment. Rotundo (University of Molise) spoke on the effects that terpenoids can have on plant-insect inter-relationships.
A very pleasant atmosphere characterized the workshop which succeded in bringing together specialists from various fields. Discussions were very fruitful and a consensus emerged on the need of cooperation between scientists whose interests range over various disciplines for the best use of these natural products. The Workshop was supported by the Italian Society of Sylviculture and Forest Ecology (SISEF) and the Phytochemical Society of Italy SIF. The proceedings of the meeting will be available soon on the SISEF homepage.
Istituto Genetica Vegetale – Sezione di Firenze
IGV – CNR
v. Madonna del Piano, snc – 50019 Sesto Fiorentino (FI)