Cytokinins in scotch pine seedling root exudates and their influence on seed germination

Thirteen-day-old Scotch pine (Pinus sylvestris) seedlings were grown in bidistilled water under sterile conditions at either 6°C or 21 °C for 6 days. Concentrated water exudates were purified by a cellulose phosphate and fractionated by high performance liquid chromatography. Cytokinin-like activity of the collected fractions was detected by the Amaranthus bioassay. The highest cytokinin activity corresponded to the retention time of zeatin riboside (ZR), which was also confirmed by gas chromatography-mass spectrometry. Low biological activity was also detected in the fractions co-eluting with isopentenyladenosine (2iPA) and isopentenyladenine (2iP) standards. The influence of temperature changes on cytokinins was more quantitative than qualitative, as a four times higher activity was detected in root exudates collected from seedlings grown at 21°C than those grown at 6°C