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ISHS Acta Horticulturae 1134: VIII International Symposium on Light in Horticulture

Effect of intracanopy lighting and/or root-zone temperature on high-wire tomato production under supra-optimal air temperature

Authors:   C. Gómez, M. Clark, C.A. Mitchell
Keywords:   high-wire tomato, LEDs, soilless culture, root-zone cooling, solid-state lighting
DOI:   10.17660/ActaHortic.2016.1134.9
Abstract:
The effects of providing intracanopy lighting to mutually shaded leaves using light-emitting diodes (ICL-LED; 93% red and 7% blue) and/or root-zone temperature were evaluated as strategies for stimulating high-wire greenhouse tomato (Solanum lycopersicum LSQUOFelicityRSQUO) production during summer conditions in a mid-northern climate (lat. 40°N). Plants were grown in a glass-glazed greenhouse with ambient day temperatures at or above 30°C. Four treatments were evaluated in the study: 1) ICL-LED, which provided an average daily light integral (DLI) at mid-canopy height of 4 mol m-2 d-1; 2) Root-zone cooling (RZC) at 18±2°C; 3) ICL-LED + RZC; and 4) control for which no treatment was applied. ICL-LED was used as a potential stimulator of gas exchange and, thus, was expected to promote evaporative cooling within the canopy. RZC was used as an approach to reduce thermal stress in supraoptimal air-temperature conditions. Weekly plant-growth measurements, productivity, and leaf gas-exchange responses (stomatal conductance (gs), transpiration (E), and CO2 assimilation (A)) were measured for plants in each treatment. No significant differences were observed for any physiological or harvest parameters evaluated. However, ICL-LED + RZC increased leaf length relative to control. Results suggest that neither ICL-LED (in the spectral composition used in our experiment) nor RZC are viable strategies to promote growth or productivity for greenhouse-tomato production during summer conditions in a northern climate.

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