AXILLARY BUD DEVELOPMENT OF POINSETTIA ECKESPOINT-LILO AND ECKESPOINT-RED-SAILS (EUPHORBIA-PULCHERRIMA WILLD) IS INHIBITED BY HIGH-TEMPERATURES

The effect of temperature on axillary bud and lateral shoot developmen t of poinsettia (Euphorbia pulcherrima Willd.) 'Eckespoint Lilo' and ' Eckespoint Red Sails' was examined. Rooted 'Eckespoint Lilo' cuttings were transplanted and placed into growth chambers maintained at 21, 24 , 27, or 30 degrees C for 2 weeks before apex removal, The percentage of nodes developing lateral shoots after apex removal was 68%, 69%, 73 %, or 76% at 21, 24, 27, or 30 degrees C, respectively. Cuttings were removed from the lateral shoots, roofed, and placed into a 21 degrees C greenhouse, and the apices were removed, The percentage of nodes dev eloping into lateral shoots on cuttings taken from plants held at 21,2 4,37, and 30 degrees C were 74%, 65%, 66%, and 21%, respectively. Of t he cuttings in the 30 degrees C treatment, 83% of the nodes not produc ing a lateral shoot had poorly developed axillary buds or no visible a xillary bud development. Visual rating of axillary bud viability decre ased from 100% to 0% when 'Eckespoint Red Sails' plants were transferr ed from a 21 degrees C greenhouse to a greenhouse maintained at 27 deg rees C night temperature and 30 degrees C for 3 hours followed by 33 d egrees C for 10 hours and 30 degrees C for 3 hours during the 16-hour day. Transfer from the high-temperature greenhouse to a 21 degrees C g reenhouse increased axillary bud viability from 0% to 95%. Axillary bu ds of Leaves not yet unfolded were sensitive to high temperatures, whe reas those of unfolded leaves (i.e., fully developed correlatively inh ibited buds) were not. Sixteen consecutive days in the high-temperatur e treatment were required for axillary bud development of 'Eckespoint Red Sails' to be inhibited.