Pinching technique influences lateral shoot development in poinsettia
Berghage, R.D. | Heins, R.D. | Karlsson, M. | Erwin, J. | Carlson, W.
Lateral shoot growth and plant morphology of poinsettia (Euphorbia pulcherrima Willd.) were influenced by the pinching technique used for apical meristem removal. Plants were pinched in one of four ways: 1) soft (removal of the apical meristem plus stem and leaf tissue associated with leaves less than or equal to 2 cm long); 2) medium (removal of the apical meristem plus stem and leaf tissue associated with leaves up to 7 cm long); 3) hard (removal of the apical meristem plus stem and leaf tissue associated with all immature leaves); and 4) leaf removal (LR; soft pinch as defined above plus removal of all immature leaves but not the associated stem tissue). Initial growth of lateral shoots on soft and some medium-pinched plants was less than initial growth of lateral shoots on hard- or LR-pinched plants. Shorter lateral shoots and longer primary stems at anthesis on soft-pinched plants resulted in vertical plant architecture. Hard- and LR-pinched plants had a more horizontal plant architecture. The average height : width ratio of soft-, hard-, and LR-pinched plants at anthesis was 0.77, 0.68, and 0.63, respectively. Of 10 commercial cultivars tested in 1987, 48% of the inflorescences of soft-pinched plants developed below the bract canopy, compared with 27% and 31% for hard- and LR-pinched plants, respectively. These results show that the use of a soft pinch to increase inflorescence number in the bract canopy is not productive if immature leaves are left on the plant when pinching.
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