The effects of nitrogen fertilization on the ultrastructure of mesophyll cells of conifer needles in northern Finland

Abstract Cytological injuries in needles of Scots pine ( Pinus sylvestris L.) and Norway spruce [Picea abies (L.) Karst.] were studied at light and electron microscope level in northern Finland. Needle samples were taken from fertilized (mainly with nitrogen) and nonfertilized trees during winter 1980. The results are discussed in relation to the severe climate and growth response of the trees.