End-of-day Far-red Light Quality and Dose Requirements for Tomato Rootstock Hypocotyl Elongation

Abstract

<jats:p>Plant morphology control is a critical technique in commercial greenhouse transplant production. Light treatment at the end of the day affects a phytochrome-regulated response affecting plant height among other characteristics and has been studied by biologists for many years. Recognizing the need to produce long hypocotyls in vegetable grafting, effects of end-of-day far-red (EOD-FR) light on tomato rootstock hypocotyl elongation were investigated. Two commercial rootstock cultivars, Aloha (<jats:italic>Solanum lycopersicum</jats:italic>) and Maxifort (<jats:italic>S. lycopersicum</jats:italic> × <jats:italic>S. habrochaites</jats:italic>), were used for the experiments examining responses to EOD-FR light quality [red to far-red ratio (R/FR)] and EOD-FR light dose in a greenhouse environment. In the EOD-FR light quality experiment using ‘Aloha’ seedlings, incandescent light (R/FR = 0.47) induced significant hypocotyl elongation (20%) compared with the untreated control. Incandescent light with a spectral cut filter (reducing R/FR to 0.05) induced a greater hypocotyl elongation (44%) than unfiltered light, confirming the importance of use of light with a lower R/FR (or purer FR) light source in EOD-FR treatments. In the experiment on EOD-FR light dose–response, hypocotyl elongation of both ‘Aloha’ and ‘Maxifort’ was increased by increasing FR intensity as well as FR treatment duration at a lower dose range. The dose saturation curve of hypocotyl length was well described using a Michaelis-Menten-type model with FR dose (in mmol·m<jats:sup>−2</jats:sup>·d<jats:sup>−1</jats:sup>) as an independent variable. The model-based estimation of 90% saturating FR light dose for ‘Aloha’ and ‘Maxifort’ was 5 to 14 mmol·m<jats:sup>−2</jats:sup>·d<jats:sup>−1</jats:sup> and 8 to 15 mmol·m<jats:sup>−2</jats:sup>·d<jats:sup>−1</jats:sup>, respectively, although practical near saturation dose seems to be 2 to 4 mmol·m<jats:sup>−2</jats:sup>·d<jats:sup>−1</jats:sup> for both cultivars. None of the EOD-FR treatments affected plant dry weight, stem diameter, or plastochron index. Hence, elongation was achieved without compromising growth and development. EOD-FR was shown to be an effective non-chemical means allowing transplant propagation industry to produce long hypocotyls for grafting use.</jats:p>

Influence of Different Photoperiod and Temperature Regimes on Growth and Bulb Quality of Garlic (Allium sativum L.) Cultivars

“…G024 with the lowest bulb characteristics, showed the lowest nutritive quality traits (Table 4). Similar to the bulb characteristics, the photoperiod and temperature treatments significantly increased the protein and sugar content ( Table 1, 3,4). Moreover, the longer photoperiod (L14) and higher temperature (T30) had a significantly improving effect on the nutritive quality traits among the photoperiod and temperature treatments which is similar to the increasing trend of BI.…”

Regulating Flowering and Extension Growth of Poinsettia Using Red and Far-red Light-emitting Diodes for End-of-day Lighting

“…Promotion of stem length can be achieved by providing EOD lighting, and a low R:FR is typically more effective than a high one. For example, the hypocotyl length of tomato seedlings under 12-min EOD lighting treatment, regardless of light quality, was 20% to 44% greater than that without an EOD treatment (Chia and Kubota, 2010). In addition, the hypocotyl length under EOD lighting with an R:FR of 0.05 was 20% greater than under EOD lighting, with an R:FR of 0.47.…”

Tomato seedling physiological responses under different percentages of blue and red photon flux ratios using LEDs and cool white fluorescent lamps

“…Spectral customization can be used to increase desirable plant characteristics. For example, special light formulations can increase plant growth rate and production (Eguchi et al, 2016a;Ouzounis et al, 2016;Runkle and Park, 2016), increase the concentration of secondary metabolites in plant tissue (Goto et al, 2016;Li and Kubota, 2009;Nicole et al, 2016;Noguchi and Amaki, 2016;Samuoliene et al, 2012), promote plant development (Gilberto et al, 2005), and generate desirable plant morphology (Chia and Kubota, 2010;Hernández and Kubota, 2015;Jeong et al, 2014;Yang et al, 2012).…”