DECAY RESISTANCE IN CONIFER SEED CONES - ROLE OF RESIN ACIDS AS INHIBITORS OF DECOMPOSITION BY WHITE-ROT FUNGI

Resin acids in the diethyl ether extracts of Picea glauca, Pinus ponde rosa and Pinus banksiana seed cones were identified by gas-liquid chro matography of their methyl-ester derivatives. For these seed cones, ab ietic, dehydroabietic and isopimaric acids comprised 63.7-80.5% of the total resin acids identified. In P. banksiana, the resin acid composi tion of the seed cones was shown to be significantly different from th at in either the leaves, bark or wood. Investigation of the role of re sin acids in the apparent decay resistance of woody conifer tissues to white-rot fungi involved the incorporation of abietic, dehydroabietic and isopimaric acids individually, or as a 1:1:1 mixture, into decay susceptible sweetgum (Liquidambar styraciflua) wood test blocks which were subsequently exposed to cultures of Irpex lacteus and Trametes ve rsicolor Inhibition of decay by I. lacteus was observed for test block s treated with abietic and dehydroabietic acids, but not isopimaric ac id. With T. versicolor, only those test blocks treated with abietic ac id showed less decay when compared with controls. Comparisons of the d ecay levels with the moisture contents of resin acid treated test bloc ks, and the analyses of residual resin acid contents of decayed blocks , indicate that resin acids provide decay resistance by their water re pellency and inherent decay resistance rather than general toxicity.