Nutritive stress and cytokinin status in Norway spruce seedlings (Picea abies L. Karst.)

The content of cytokinins was analysed in shoots and roots from spruce seedlings ( Picea abies L. Karst.) grown on various hydroculture media either with complete nutrient supply ( control medium) or with deficiencies for some nutrients ( stress medium). The cytokinins zeatin riboside and isopentenyladenosine were determined by an indirect competitive enzyme-linked immunosorbent assay ( ELISA) in HPLC-purified extracts. The shoots of spruce seedlings grown on stress medium plus aluminum ions (Al3+, 0.8 mM) showed approximately 5-fold higher concentration of zeatin riboside and isopentenyladenosine than the controls. When the auxin naphtylacetic acid ( 1 mu M) was added to the stress medium, also higher levels of cytokinin ribosides were measured in the shoots. In the roots however, cytokinin riboside levels did not increase significantly, neither under Al3+ nor auxin treatment. The model experiments with spruce seedlings grown under controlled conditions support previous monitoring data on declining forest stands and show that nutritive stress can significantly increase the cytokinin content in the shoot of Norway spruce.