Common physiological mechanisms prepare seeds with different dormancy types for germination

The processes preparing for the initiation of cell elongation were studied in the axial organs of germinating horse chestnut Aesculus hippocastanum seeds. Under cold stratification, seeds are in the state of deep dormancy for one month, then dormancy is gradually released over a 2.5-month period. The breaking of deep dormancy is controlled by cytokinins: thus, treating seeds with 2 x 10(-4) M benzylaminopurine increased the rate of this process twofold. When non-dormant seeds were kept in a 30% polyethylene glycol solution, they did not germinate; this evidence indicates that an increase in moisture content is essential to prepare cells for elongation. The processes of cell preparation for elongation are regulated by an increase in moisture content and comprise the accumulation of osmotic solutes (sugars and potassium ions) and the acidification of cell walls. By comparing the processes that occur in the axial organs of horse chestnut, broad bean, and wheat seeds during cell preparation for elongation, we have demonstrated common patterns characterizing germination in both orthodox and recalcitrant seed with different types of dormancy.