Metabolism of carbon-14-labeled benzene and tolueue in avocado fruit.

The uibiquitouis occturrence of hydrocarbons including mlany aromiatics in plants has been the subject of ain extensive, careful review (2). However. the origin andI metabolisnm of the aromatic hydrocarbons in plaint tissue has received little attention. The intriguilng possible biogenesis of aromatics from the prevalent lpolyacetylenes in plants has been suggested (7). P'reviouis reports from ouir laboratory demlonstrated that benzelne anid tolulene occur pcr sc in green av7ocado fruit ( 3, 4, 5). Ak study of the mnetabolisn of ethyle,ne in green, mature avocado fruit demonstrated the conversion of etlhvlene-2H to benzen.e-3H and toluene-"H and the conversion of ethlvlene-14C to benzene-_4C andcl toluene-' 'C in this frtit (3, 4). Approximately one-eiglhth of the total inicorporated radioactivity of mletabolize(d ethv-lene-:H was converted to toluene-31H witlh al)lroximatelv 95 %ofthe radioactivity of the toluiene located in the miethyl grouip (3). The metabolism of ethvlene-14C results in a muclh smaller anmouniit of label into toliene (4). The incorporation of tritiumil and(I 14C fromli labeled ethvlene into benzene is 1 % and 4 %. respectively (4). Compar-ed to ethylene, acetylene is a better prectursor of beqIzene buit not toltiene (5). Therefore, a study of the metabolisml of 4'C-labeled benzene and toluene by this frtuit was undertaken. It has now been fouind that these 2 aromlatic hydrocarbons are mletabolized by avocado fruit, toltuenie mlore extensivelv thain benizene, to produce volatile anid lnonvolatile metabolites of as vet unknow,-n nature. Both hydrocarbonis are metabolized to a smlalll but signiificant exten,t to CO_. Phy\siologically\, both benzene and toluene vapors produce chalnlges in ripening avocado fruit. However, the level of these hydrocarbons wvhich produce a visuial effect w-as fotind to be several huindred times tlhat u.ied in the present tracer exl)eriments (unptlblisledl resuilts). The method of exposing avocado fruit to 14Clabeled benzene or toluienie ( fromol New England