|
|
|
| The formation of terpenoid defense compounds in conifers in relation to physical and biological stresses |
|
Jonathan Gershenzon
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA., U.S.A.Max Planck Institute for Chemical Ecology, Carl-Zeiss-Promenade 10, D-07745 Jena, Germany
|
One of the major defense systems of conifers against herbivores and pathogens is the production of terpenoid-based resins. The major constituents of conifer resins are volatile monoterpenes and non-volatile diterpene acids with lesser amounts of sesquiterpenes and phenolic compounds. These substances accumulate in specialized structures, including resin ducts and resin cells, found in stems, roots, foliage and cones. Extensive research has been carried out on the influence of various physical and biological stresses on resin accumulation in conifer stems, and several general patterns have been noted. Stem resins can be produced constitutively or in response to wounding, insect or fungal attack. While constitutive stem resin is often formed during periods when growth is suppressed by water or nutrient stress, induced resin formation usually occurs at a higher rate during active growth phases than during other periods. Foliage resin is produced during various stages of needle development and both synthesis and volatilization are also influenced by biotic and abiotic factors. These patterns have been explained by reference to several classic theories on the distribution of defense compounds in plants. They can also be explained in light of recent advances in terpene biochemistry which helps in understanding how allocation to growth versus defense is modified under changing environmental conditions.
|
|
|
|
