Ultrastrukturelle Veränderungen in grünen Nadeln geschädigter Fichten

The ultrastructure of green needles from a Norway spruce tree with severe symptoms of forest decline was compared with that of needles from an apparently unaffected tree. No structural changes were found in the mesophyll cells and endodermis of current year needles from both trees. However, in the transfusion parenchyma of needles the damaged tree a disdintegration of the cytoplasm was evident; plastids showed reduced grana and an increased number of plastoglobules. In the previous needles from the damaged tree no differences were found in the mesophyll ultrastructure when compared with the corresponding needles of the unaffected tree. In addition to the destructive alterations of the transfusion parenchyma the plastids in the endodermis were also damage. Furthermore, sieve elements adjacent to the cambium showed reduced lumina, indicating an obstruction of the phloem transport. - This pattern of histological changes does not correspond with the effects described for direct exposure of conifer needles to phytotoxic gases. Obviously the damage observerd is not primarily induced by air pollutants invading the needle tissue via cuticle and/or stomata.