Abstract
Capabilities of organisms and their roles can be viewed from two aspects : social relation for the maintenance of ontogeny and social relation for the maintenance of phylogeny. Chemical communication capabilities of organisms and their roles can be seen in a similar way. Because higher plants are sessile organisms, they utilize physical phenomena such as wind and water, and organisms such as insects, birds, or mammals for their mating and dispersal of seeds to maintain their lineage. Their form of evolution has been unique and different from that of animals. Their functions for mating include perfume, flowering season, flower form, flower color, nectar ; the functions for dispersal are perfume, fruit form, sarcocarp, and elaiosome.
Betula, a relatively new lineage of plant, utilizes anemophily and anemochory for its mating and dispersal of seeds. Since the plants of this genus synchronize their flushing and flowering using fragrance, the utilization of anemophily for chemical communication by plants can be judged as relatively new.
Plants (consumer) are inevitably prey for animals. Therefore, plants have evolved protective abilities to maintain ontogeny. To protect their leaves from defoliators either chemically or physically, plants have evolved poisons such as tannin, alkaloid, and terpene. When defoliators chew the leaves of Betula platyphylla, leaf alcohol (cis-3-hexen-1-ol), which is a stabilized alcoholic substance, is biosynthesized from linolenic acid, one of the constituents of the leaf. When dispersed in the air, leaf alcohol effects as an ecomone. Leaf alcohol is the ecomone of Betula, which induces other leaves to produce antifeedant, 3,4′-Dihydroxypropiophenone-3-β-D-glucopyranoside (DHP-Glu.) ; it acts as ecohormone in the other leaves of the same organism, and as a pheromone in the leaves of other individual organisms of the same species, and as allelochemics in the leaves of other species. The term ecohormone is established for chemical messages between leaves of a individual. If newborn hatchlings eat a leaf that contains large amounts of phenol (DHP-Glu.), almost all of them will die. Thus, leaves keep defoliators from proliferating. Leaf alcohol can be said to be a common semiochemical in all plants to protect themselves from defoliators.
