Many lichen phenolics act as allelopathic substances, lowering germination and growth rates of higher plants or even promoting their decay. Physiological observations previously made on the effect of Evernia prunastri (L.) Ach. lichen compounds on Quercus rotundifolia Lam. explants were correlated in this work with the ultrastructural alterations in chloroplasts. The degenerative changes included the swelling and collapse of granal and agranal thylakoids, with a peripheric display of lamellae and an increase in the number and size of plastoglobuli, though not as high as described elsewhere. Besides these eífects, that are in line with the pattern of breakdown of chloroplasts of leaves senescing under natural conditions, bundles of fibrillar formations were found in the stroma. Transverso sections through these stromacentre-like formations showed their paracrystalline structure, made of hexagonal subunits with an electron-transparent core and a dense outline, the centre-to-centre spacing was 13 nm.

6 pages, figures, and tables statistics.

Peer reviewed