PINE BARK LEVELS AND PARTICLE SIZE INFLUENCE THE ACTIVITY OF PACLOBUTRAZOL AND UNICONAZOLE ON `FREEDOM' AND `GUTBIER' V-14 GLORY POINSETTIAS

in HortScience
Authors:
Jesse R QuarrelsDepartment of Plant and Soil Sciences, Box 9555, Mississippi Agricultural and Forestry Experiment Station, Mississippi State, MS 39762

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Steven E. NewmanDepartment of Plant and Soil Sciences, Box 9555, Mississippi Agricultural and Forestry Experiment Station, Mississippi State, MS 39762

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A study was conducted to determine the effects of pine bark grind size and pine bark levels on the activity of two growth regulators on poinsettia Two bark grinds (≤ 6 mm and >10 mm) were used with four media combinations within each grind: vermiculite:bark:peat moss at 2:0:3, 2:1:2, 2:2:1, and 2:3:0 (by volume). Two growth regulators, paclobutrazol and uniconazole, were applied at 0, 0.125, and 0.250 mg/15 cm container in 250 ml water. Two poinsettia cultivars, `Freedom' and `Gutbier V-14 Glory', were planted September 2, 1993, pinched September 16, and growth regulators applied September 30. There were five single plant replications for each treatment. Stem length and bract area were effected by bark grind, bark level, growth regulator, and growth regulator rate. Plants treated with uniconazole had the shortest stems and the least bract area. Plants grown in the smaller grind and at higher bark levels were less effected. Plants treated with paclobutrazol had longer stems than those treated with uniconazole.

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