Delignification of subsidiary and guard cell walls of Picea abies (L.) Karst. by fumigation with ozone

Summary After fumigation with ozone, the exterior periclinal walls of the stomatal apparatus of Picea abies appear to be partially delignified, as in earlier experiments with SO₂. This shows up cytophotometrically as reduced UV absorption. Random samples from the stand named Wank in the Bavarian Alps clearly showed a relation between the degree of lignification of the stomatal cells and the grading of the respective trees in their damage classes. The significance of delignification for the regulatory capacity of the stomata is discussed, and a hypothesis is proposed for a specific disturbance of hydroregulation by ozone.