The Relationship between Maturity Level and Splitting in Poinsettia

Abstract

<jats:p>The relationship between poinsettia <jats:italic>(Euphorbia pulcherrima</jats:italic> Willd. ex Kl.) maturity and premature flower bud initiation (splitting) was evaluated. Changes in root growth, phyllotaxy, and heterophylly of `Annette Hegg Dark Red' poinsettia stock plants and cuttings in response to repeated severe pruning (hedging) and the chemical growth regulators gibberellic acid (GA<jats:sub>4+7</jats:sub>), PBA, or ethephon were evaluated. Cuttings taken from hedged stock plants exhibited a phyllotaxy of 1/3 to 2/5, extensive root growth (characteristics of juvenility in poinsettia), and a low level of splitting (34%). Cuttings taken from nonhedged stock plants exhibited a phyllotaxy of 3/8, reduced root growth (characteristics of maturity in poinsettia), and a high level of splitting 177%). There was a moderate negative correlation (-0.75) between root growth and splitting and a strong positive correlation (0.94) between splitting and phyllotaxy. Cuttings treated with gibberellic acid or PBA exhibited elliptic to ovate leaves (a juvenile characteristic) and levels of splitting ranging from 20% to 90%, depending on concentration and application timing. Untreated cuttings and those treated with ethephon exhibited lobed leaves (an adult characteristic) and levels of splitting ranging from 82% to 100%. Names of the chemical growth regulators were: trihydroxy-1-methyl-8-methylenegibb-3-ene-1,10-dicarboxylic acid 1,-4a-lactone (GA<jats:sub>4+7</jats:sub>); N-(phenylmethyl)-9-)tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (PBA); (2-chloroethyl) phosphonic acid (ethephon).</jats:p>

Meristem Ontogenetic Age as the Controlling Factor in Long-day Floral Initiation in Poinsettia

“…The consistency and predictabilty of the LDNN of a given cultivar supports this assumption. In addition, Siraj-Ali et al (1990a) demonstrated that severe pruning (hedging) of stock plants had a rejuvenating effect on poinsettia plants.…”

Number of Stock Plant Shoot Nodes Influences Splitting of `Lilo' Poinsettia

“…Induction is followed by the development of vegetative shoots (usually three) just below the terminal flower bud, resulting in a "splitting" of the main stem. Splitting (more specifically, flower bud induction) of vegetative poinsettia stems has been closely and positively correlated to the mature developmental phase (Siraj-Ali et al, 1990b).…”