Effect of exogenous growth regulators on flowering and cytokinin levels in azaleas

Abstract

‘Alaska’ and ‘Redwing’ azaleas having dormant flower buds were sprayed with gibberellins (GA 3 or GA 4 + 7) alone and in combination with thiourea, N 6 benzyl adenine (BA) or kinetin weekly for 3 or 4 weeks to test the efficacy of these materials in breaking bud dormancy. Additional plants received 6 weeks of cold storage at 4.5°C or glasshouse day temperatures of 21°C and above. The 2000 and 3000 mg l −1 GA 3 and Ga 4 + 7 sprays were better than 1000 mg l −1 in promoting flowering, with ‘Redwing’ responding better than ‘Alaska’. GA-treated plants flowered in fewer days than those receiving cold storage. Flower diameter and pedicel length increased with higher levels of GA, and flower uniformity was comparable to cold-stored plants on most GA-treated ‘Redwing’-plants. Thiourea, BA and kinetin applied alone had no effect and considerable cytokinin activity was highest in GA-treated buds 14–21 days after treatment application. No increase in activity occurred on plants not receiving GA.