Light and electron microscopic investigations on wound reactions in the bark of Salix caprea L. and Tilia tomentosa Moench.

Abstract

Wound reactions of bark of Salix caprea L. and Tilia tomentosa M oench . were observed with light and electron microscopy a few hours and 1, 2, 3, 7, 10, 14, 21, 28, 35, 42 and 84 days after artificial wounding. At first phenolic substances are produced resulting in a brown discolouration close to the wound. After 7–14 days lignification of a tissue zone starts followed by suberisation of this zone after 14–21 days. After 28–42 days this reaction zone completely surrounds the wound and the formation of a wound periderm has started. Suberisation occurs at two different stages. In cells already present before wounding, a suberised layer is deposited onto the inner surface of secondarily lignified primary or secondary walls. In addition, suberised phellem cells are produced by a wound phellogen. TEM observations reveal that the suberin layer of the secondarily lignified cells and newly formed phellem cells possess a polylamellate structure. Most cells of the reaction zone appear very active as indicated by their cytology, but it is not possible to attribute the ultrastructural activity to suberisation.