EFFECT OF CALCIUM, BORON AND MOLYBDENUM ON PLANT GROWTH AND BRACT PIGMENTATION IN POINSETTIA

Foliar sprays of Ca (300, 400, and 500 mg L-1), B (0.2, 0.5, and 0.8 mg L-1), Mo (0.3, 0.4, and 0.5 mg L-1), Ca + B (400 + 0.5 mg L-1), Ca + Mo (400 + 0.4 mg L-1), B + Mo (0.5 + 0.4 mg L-1) and Ca + B + Mo (400 + 0.5 + 0.4 mg L-1), were applied to improve the quality of poinsettia plants (Euphorbia pulcherrima) cv. ‘Supjibi Red’. Treatments were applied three times at: beginning, middle, and end of the short photoperiod. Calcium at 400 mg L-1 increased significantly plant height by 15.3 %. Leaf chlorophyll concentration decreased by 25 % when bract pigmentation initiated. Treatments did not affect the leaf chlorophyll contents. Calcium (300 mg) and B (0.8 mg) increased the number of transitional bracts (5.7 and 5.6, respectively) compared to 0.4 mg L-1 Mo treatment; while B (0.5 mg) increased the total number of colored bracts per shoot (8.36) compared to the rest of the treatments. Total chlorophyll concentration decreased by 95 % in transitional bracts, carotenoids decreased 89 % and anthocyanins increased considerably (from 21.4 to 296.7 mg g-1). Foliar applications of calcium improved poinsettia plant height and the Ca plus B combination accelerated bract pigmentation.