PHENOLOGY OF AND HEAT UNIT REQUIREMENTS FOR GROWTH IN PROTEA 'CARNIVAL' INDUCED BY BENZYLADENINE-CONTAINING GROWTH REGULATORS

Abstract

Benzyladenine (BA) application to induce budbreak and inflorescence initation in mature shoots in late summer to autumn has been studied as a tool for manipulation of flowering time in Protea. Dormant terminal buds on three-flush shoots of eight-year-old Protea 'Carnival' plants were treated with a single application of 500 mg·L -1 benzyladenine (BA), prepared by diluting either ABG-3062 (2% active ingredient w / w ) or Accel ® (1.8% active ingredient w / w ). Treatment dates were spaced two weeks apart starting from 14 March until 22 May 2003. Three phenological stages and the days required to complete each stage was recorded for all treatments. Monitored stages included: date of ABG-3062 or Accel ® application to green point; green point to cessation of induced shoot elongation and from the latter until anthesis. Base temperatures of 9, 6 and 1°C were determined for the respective stages. Between 17-57 days were required from date of ABG-3062 application to green point. No significant difference was obtained for means of Accel and ABG-3062 treatments. The number of days required from cytokinin application to green point was negatively correlated with the mean temperature that prevailed for that period. Shoots required approximately 5400 growing degree hours (GDH) to complete this phenological phase. The relationship between temperature and the number of days required to complete the phase 'green point to cessation of shoot elongation' was not clear. The phenological phase of 'cessation of shoot elongation to inflorescence anthesis' needed between 121-177 days to completion and the duration was negatively correlated with the prevailing temperatures. Inflorescences on three-flush shoots required between 53300 and 54400 GDH to anthesis.