Changes in Ribonuclease Activity and Content of RNA during Dormancy and Growth of Bird‐cherry Buds

Ribonuclease has been extracted from buds of bird‐cherry (Prunus padus L.) by a three‐step method. In step 1 ribonuclease was extracted from the homogenized tissue at pH 6. In step 2 the tissue residue from (1) was extracted at pH 7. In step 3 the tissue residue from (2) was extracted with a buffer of pH 8.5 and containing 0.7 M KCl. The ribonuclease from step 1 and 2 is named soluble and that from step 3 bound ribonuclease. The activity of the soluble ribonuclease was very low in October and increased slowly until March. When the buds sprouted in April the activity of this fraction rose rapidly. The activity of the bound ribonuclease was rather high in October and increased continuously from autumn to spring. RNA accumulated slowly between autumn and spring. The change in activity of the two ribonuclease fractions is discussed in relation to development.