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Role of Gibberellins in Chrysanthemum Growth under Far Red Light-deficient Greenhouse Environments

2002; American Society for Horticultural Science; Volume: 127; Issue: 4 Linguagem: Inglês

10.21273/jashs.127.4.639

2327-9788

Sonja L. Maki, Sriyani Rajapakse, Robert Ballard, Nihal C. Rajapakse,

Flowering Plant Growth and Cultivation

Plants grown in far red (FR) light deficient environments are typically shorter because of short internodes, resembling plants treated with GA biosynthesis inhibitors. The role of GAs in the reduction of stem elongation of `Bright Golden Anne' chrysanthemum [ Dendranthem × grandiflora (Ramat.) Kitam. (syn. Chrysanthemum × morifolium Ramat.)] grown in FR light deficient (-FR) environment was investigated by following the response of chrysanthemums grown in - FR environment to exogenous application of GA 1 , GA 19 , or GA 20 , and the metabolism of GA 12 and GA 19 in -FR or +FR environment. FR light deficient environment resulted in 25% to 30% shorter plants than in +FR environment. Final height of GA 1 - and GA 20 -treated plants followed a quadratic pattern while that of GA 19 treated plants followed a linear pattern as the dosage increased from 0 to 50 μg/apex. The response to GA 1 was the greatest followed by GA 20 and GA 19 , regardless of the light environment. Application of GA 1 (50 μg/apex) increased final height by 65% compared with no GA (0 μg/apex) application under either +FR or -FR light environment, suggesting the response to GA 1 , which is the active form, remained the same. Responses to GA 19 and GA 20 declined under -FR light. [ 14 C]GA 12 and [ 14 C]GA 19 metabolized slowly in the -FR environment suggesting that the turnover of GAs may have caused in part the lower response to GA 19 . Although metabolism of GA 1 under -FR environments was not investigated, observations with GA 1 application experiments support that -FR environment may have enhanced inactivation of GA 1 . Chemical name used: gibberellic acid (GA).