HORMONAL-CONTROL OF DORMANCY AND APICAL DOMINANCE IN TISSUE-CULTURED PLANTS

In many crops, it is important to control dormancy and/or apical dominance during micropropagation. The regulation of dormancy was studied in bulblets of lily, buds of apple and quince, and seeds of Agrostemma githago. The development of dormancy was enhanced by choosing the appropriate tissue-culture conditions, in particular temperature, and inhibited by application of fluridone, an inhibitor of abscisic-acid (ABA) synthesis. For the maintenance of dormancy, continuous synthesis of ABA was required. Dormancy was broken by treatment with gibberellins, or by cold storage under humid conditions. Apical dominance was studied in apple. As a pretreatment with fluridone promoted the outgrowth of axillary buds, ABA may also play a role in the development of apical dominance.