Apple Fruit Bud Development and Growth; Analysis and an Empirical Model

Analysis of the information available on apple bud development and growth after dormancy leads to an empirical model of growth to full bloom. The analysis and model are set in the framework of the physiological mechanisms considered to be responsible for dormancy and subsequent bud growth. It is necessary to introduce an arbitrary ‘growth unit’ scale to describe these processes quantitatively, which is done by the equation G = A/(I+be−k(I).P) where G and A are in growth units, the value of k is controlled by a dormancy index I and P is a temperature summation. The model fulfils the main requirements laid down for it and the values of P at full bloom, derived from controlled environment work and field observations, are very similar.