Cytokinins in the Spring Sap of Curly Birch (Betula pendula f. carelica) and the Non-Curly Form

The different forms of cytokinins in the spring sap fo curly (f. carelica) and non-curly birch (Betula pendula) were determined by two preparation methods, with (1) or without (2) acid hydrolysis, and were fractionated using a column of Sephadex LH-20 eluted with 35 % ethanol. The levels of cytokinins in the fractions were estimated with theAmaranthus caudatus explant bioassay and the total cytokinin contents were calculated on amino nitrogen, total sugar and sap volume bases. Using method 1, the cytokinin activities eluted mainly in the zeatin fraction, curly birch sap containing 5.2 to 8.9 times more than non-curly birch. Using method 2, the highest activities were found in more polar fractions than zeatin. The total activities found were lower than with method 1, and, again, the contents of the curly birch sap were 1.9 to 3.6 times higher. The higher cytokinin content of the curly birch sap may explain the poorer apical dominance of curly birches, and possibly even the curly-grained wood formation itself, which can be interpreted as being due to a gall-type cell division activity. Some environmental factors responsible for the onset of the curly wood formation may work through cytokinins.