Effect of exogenous growth regulators on flowering and cytokinin levels in azaleas |
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Authors: | JN Joiner O Washington CR Johnson TA Nell |
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Institution: | Department of Ornamental Horticulture, IFAS, University of Florida, Gainesville, FL 32611 U.S.A. |
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Abstract: | ‘Alaska’ and ‘Redwing’ azaleas having dormant flower buds were sprayed with gibberellins (GA3 or GA4 + 7) alone and in combination with thiourea, N6 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 GA3 and Ga4 + 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. |
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