Studies on the Contribution of Lignin and Suberin to the Impedance of Wounded Carrot Root Tissue to Fungal Invasion

Summary During repair, phloem parenchyma cells near wound surfaces accumulated suberin and lignin. At 15 °C, all cells in the surface layer had become suberized within 48 h of wounding but lignification was slower, reaching a maximum at 168 h and the distribution was patchy. When fresh wounds were inoculated with Fusarium culmorum, Botrytis cinerea or Mycocentrospora acerina, patterns of lignification were not related in a simple way to pathogenicity; only Mycocentrospora acerina was stimulatory and remained localized in the wound surface bounded by heavily‐lignified cells. If a 250 μm layer of tissue was removed from the surface of fresh or healed wounds its high impedance to Mycocentrospora acerina was substantially reduced by removal of antifungal substances. We therefore conclude that the development of structural barriers is less important than the accumulation of antifungal substances in the resistance of healing wounds. A method for the quantitative estimation of lignin is described.