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Response of Poinsettiasto Paclobutrazol in Paint Applications




The effectiveness of a paclobutrazol/paint mix in controlling growth of poinsettia plants {Euphorbia pulcherrima) cultivars Freedom Red and Angelica Red was evaluated. Plants were grown in containers whose interior walls were coated with a flat latex impregnated with varying concentrations of paclobutrazol: 0,5, 20,80,100,150,200, and 300 mg-L"1 (0.0.032,,0.64,0.96,1.28, and1.92mg a.i. percontainer, respectively). As a comparison, onetreatment consisted ofplants drenched with 118ml/container ofa paclobutrazol solution at 3mg-L-1. Plantsgrown in containerswith the paint—paclobutrazol mixwereshorter than the control plants. Treatments involving concentrations of 100 mg»L_1 or more (even asmuch asdoubled ortripled) did not produce proportionatelyshorter plants. Root dry weights ofplants inalltreatments were notsignificantly different. However, thelength ofroots touching the internal surface ofthe container de creased with increasing growth regulator concentrations. This may help explain why doubling concentrations of growth regulator-in-paint does not produce proportionately shorter plants: roots start absorbing the growth regulator as soon as they touch the wall of the container. As a consequence, all root elongation is reduced, resulting in less root-growth regulator contact and less growth regulator uptake. More measurements of root length and root are aarerequired in order to proof this hypothesis. When paclobutrazol concentrations were higher than 100 mg^L-1, some bracts showed evidence of "crinkling."

Keywords: Euphorbia pulcherrima Flat latex Paclobutrazol /paint mix

Libraries: Floriculture

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