Abstract

ALIA-TEJACAL, Iran et al. Effect of gibberellic acid sprays on growth of five poinsettia cultivars. Rev. Mex. Cienc. Agríc [online]. 2011, vol.2, n.spe3, pp.577-589. ISSN 2007-0934.

In 2010 gibberellic acid (GA) was foliar sprayed at concentrations from 0 to 10 mg L^-1 in single applications (seven days after transplant) or double applications (seven and 14 days after transplant) in five poinsettia cultivars (Euphorbia pulcherrima Willd. ex Klotz): 'Sonora', 'Da Vinci', 'Freedom White', 'Freedom Red' and 'Festival Red'. The effects on plant height, number of branches, branch length, plant and inflorescence diameter, bract color (lightness, chrome, and hue) and chlorophyll concentration (SPAD units) were studied. Analyzing the factors separately, the results indicated that plant height increased 15% to 20% when plants were sprayed once and 21 % to 3 0% when plants were sprayed twice. Plant height increased significantly when GA concentration was 2 mg L^-1 or higher (p< 0.05). Branch length was larger when plants were sprayed twice and GA concentration was higher than 2 mg L^-1, whereas inflorescence diameter decreased only in 'Freedom White', which suggested a deleterious effect in plant quality. Bract color and chlorophyll concentration were unaffected by GA sprays. In conclusion, GA increased plant height without affecting plant quality in the cultivars studied when concentration was between 2 and 4 mg L-¹ and when solutions were sprayed twice (seven and 14 days after transplant), nonetheless, it is necessary to elucidate if GA does not affect other quality parameters such as stem firmness in follow up experiments.

Keywords : Euphorbia pulcherrima; growth regulators; height; hue.

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