In Situ Plant Canopy and Potting Medium Temperatures under Two Greenhouse Temperature Regimes

Abstract

<jats:p>Root-zone and plant canopy temperatures were continuously monitored as a poinsettia <jats:italic>(Euphorbia pulcherrima</jats:italic> Willd. ex JSI.) crop was grown in the greenhouse under warm day/cool night [(+) DT-NT] or cool day/warm night [(-) DT-NT] temperature regimes. Day temperatures were imposed from 0900 to 1700 <jats:sc>hr</jats:sc>. Light levels photosynthetic photon flux (PPF) and outside ambient air temperatures were also monitored. Temperature differences between the root-zone and plant canopy microenvironments were most extreme during the night-to-day and day-to-night temperature transition periods. The temperature difference between the plant canopy and the root zone following temperature transition periods had been previously identified as a critical factor affecting stem elongation. Overall poinsettia height was consistently shorter under the (-) DT-NT than under the (+) DT-NT environment.</jats:p>

The Effect of Daminozide and Chlormequat on the Growth and Flowering of Poinsettia and Pansy

“…The market specifi cations often include target plant heights, so the ability to control stem elongation is critical to the success of commercial growers. Many methods for height control have been suggested for greenhouse crops, including mechanical stress (Garner and Langton, 1997), differential day and night temperatures (Berghage and Heins, 1991;McAvoy, 1992), and chemical plant growth regulators (PGRs) (Bailey and Miller, 1991;Barrett et al, 1994;Fisher et al, 1996;Holcomb and Rose, 1990).…”