LIGHT AND ELECTRON-MICROSCOPIC INVESTIGATIONS ON WOUND REACTIONS IN THE BARK OF SALIX-CAPREA L AND TILIA-TOMENTOSA MOENCH

Wound reactions of bark of Salix caprea L. and Tilia tomentosa MOENCH. 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 discolo uration close to the wound. After 7 - 14 days lignification of a tissu e 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 occur s at two different stages. In cells already present before wounding, a suberised layer is deposited onto the inner surface of secondarily li gnified primary or secondary walls. In addition, suberised phellem cel ls are produced by a wound phellogen. TEM observations reveal that the suberin layer of the secondarily lignified cells and newly formed phe llem cells possess a polylamellate structure. Most cells of the reacti on zone appear very active as indicated by their cytology, but it is n ot possible to attribute the ultrastructural activity to suberisation.