ETHYLENE ACCELERATES THE BREAKDOWN OF CYTOKININS AND THEREBY STIMULATES ROOTING IN NORWAY SPRUCE HYPOCOTYL CUTTINGS

Cuttings were taken from 4-week-old seedlings of Norway spruce (Picea abies L. Karst.) raised at two different irradiation levels. Rooting experiments showed that root formation was increased by the ethylene formed by adding 1-aminocyclopropane-1-carboxylic acid ACC or Ethrel, especially in the slowly rooting cuttings grown under high light (HL). Cobaltous ion, an ethylene synthesis inhibitor, delayed rooting, especially in the easily rooted cuttings grown under low light (LL). Compounds isolated from the cuttings using immunoaffinity chromatography, on a column with antibodies against cytokinins, and separated by HPLC decreased in amount during the first week of the rooting period. An increase in ethylene production accelerated this process, especially in cuttings grown under HL, whereas cobaltous ion delayed it. We suggest that ethylene stimulates rooting by enhancing the degradation of cytokinins.