Effects of Wounding and Fungus Inoculation on Terpene Producing Systems of Maritime Pine

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Abstract
Cheniclet, C. 1987. Effects of wounding and fungus inoculation on terpene producing systems of maritime pine.—J. exp. Bot. 38: 1557–1572. The qualitative and quantitative changes occurring in terpene compounds (resin acids and mono- and sesquiterpene hydrocarbons) in phloem and xylem tissues after wounding and after inoculation with a beetle-associated fungus have been compared on maritime pines from the same clone. Simultaneously, structural events occurring in phloem have been observed, especially those concerning resin ducts and cell systems associated with terpene secretion. The terpene accumulation resulting from wounding is weak and remains limited to a short period and to a restricted tissue area. In contrast, mycelium inoculation results in an exponential enrichment (× 60 after 28 d in proximal phloem) as the enriched zone enlarges, indicating a diffusive process. In wounded phloem the neosynthesis of terpenes takes place in reactivated or supernumerary resin ducts which display structural features similar to those of active secretory cells in normal conditions. In fungus-moculated phloem, secretory ducts are first reactivated, but soon undergo a lysis, and are no longer functional when the rate of terpene accumulation is increasing quickly. The formation of terpene compounds is delocalized and occurs in non-specific intra- or extracellular spaces formed by the lysis of cell contents and/or cell walls. The synthesis probably results from the random meeting of enzymes, which can be synthesized in living parenchyma cells or released by lysis of structures involved in physiological terpene secretion (leucoplasts and endoplasmic reticulum), and of the corresponding substrates, which may be provided by degradation of cell contents (polyphenolics, hpids) or by the sieve flow.