|Authors: ||X. Hao, C. Little, J.M. Zheng, R. Cao|
|Keywords: ||light-emitting diodes, Solanum lycopersicum, supplemental light, far-red light, yield, anti-oxidants|
A study was conducted from November 2014 to April 2015 in a greenhouse (192 m2 growing area) to investigate the effects of far-red LED light on plant growth, fruit yield and quality of greenhouse tomato (Solanum lycopersicum). Twin-head (stem) transplants of tomato cultivar 'Foronti' grafted on rootstock cultivar 'Stallone' were planted into six twin-rows at 2.8 stems m-2 in the greenhouse in late November The two outside twin-rows were used as the guard row while the four middle twin-rows were divided into 16 experimental plots (24 stems per plot). Four far-red LED treatments which provided 0 (control), 8, 16, and 24 Ámol m-2 s-1 of far-red photon flux were applied to the 16 plots in a Latin-square design with 4 replications.
Overhead high-pressure sodium (HPS) lamps provided 165 Ámol m-2 s-1 of PAR to all the plots in the greenhouse.
The application of far red light and overhead HPS supplement light was started in early December with a consistent photoperiod of 16 h (1:00 to 17:00 HRS). Both lighting systems were automatically shut-off when outside global solar radiation was >300 W m-2. All 3 far-red light treatments increased the stem length in the early but not in the late stage of the greenhouse trial.
Fruit yield in the first month of fruit harvest was increased by all three far-red treatments.
However, the increase diminished in the second and third month of fruit harvest.
The fruit harvested from the plants exposed to far-red light also had higher carotenoid content.
Therefore, this study showed some beneficial effects of low dose of far red light in early stage of fruit production of greenhouse tomatoes grown under HPS lighting.
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