Dormancy and post-harvest maturation of malt barley (Hordeum vulgare L.) caryopses

During 1997 to 1999 the dormancy and process of post-harvest maturation of caryopses were studied in the Akcent and Krona malt barley varieties. In bo th varieties the deepest dormancy was observed in 1997 when rainfall was th e heaviest at the time of caryopses ripening and temperatures were, on aver age, by ca 2 degrees C lower than in the two following years. Using the ind ex and rate of germination it was possible to differentiate the Akcent and Krona varieties immediately after harvest and also during post-harvest matu ration. The greatest differences between the two varieties were found in 19 97. Caryopsis dormancy was always higher in Krona than in Akcent. In the st age of milk ripeness, when the caryopsis is the most sensitive to weather e ffects, the differences in the content of abscisic acid (ABA) were the bigg est, corresponding with the assumption that the ABA content is higher in a cooler and more humid climate when more dormant caryopses are formed. The t otal content of phenolic substances was the highest in 1997 and contributed to the level of caryopsis dormancy. Indolyl-3-acetic acid (IAA) and the ma jority of cytokinins (CK) participate particularly in the regulating proces ses associated with caryopsis filling, their content rapidly declining afte r reaching maturity.