Abstract
Although light-emitting diode (LED) lamps have been broadly applied in horticultural production to improve plant yield and quality, compared to natural light there is a disadvantage in the lack of far-red light in the LED spectrum. Far-red light has been studied widely to control plant growth and development. Therefore, this study aimed to find the effect of supplemental far-red-enriched LED lights to control the growth of tomato, red pepper, cucumber, gourd, watermelon and bottle gourd seedlings. The treatments were cool white LED:far-red LED at ratios of 5:0, 5:1, 5:2 and 5:3. The growth of tomato and red pepper seedlings, including hypocotyl length, was correlated to far-red light and light intensity. The phytochrome photostationary state (PSS) value of maximum hypocotyl length by supplemental far-red-enriched light ranged from 0.69 to 0.77 in tomato and red pepper seedlings. Although hypocotyl lengths of cucumber and watermelon were greatly affected by PSS, the PSS value for maximum hypocotyl length was lower than for tomato and red pepper. These results show that manipulating supplemental far-red enrichment can be used to control vegetable seedling growth with some variation among plant species.
Highlights
Plant responses to light may vary depending on light intensity, photoperiod and light quality
Gourd, watermelon and bottle gourd seedlings, every hypocotyl length by the supplemental far-red lights was higher than W5F0 and showed the greatest features in W5F2
A similar result of quadratic relationships with peak values was reported with Crepidiastrum denticulatum [34], similar to our results with tomato and red pepper seedlings
Summary
Plant responses to light may vary depending on light intensity, photoperiod and light quality. As far-red light intensity increased, plant growth and morphology were affected in lettuce (Lactuca sativa L.) [1,4,5,6], tomato (Solanum lycopersicum L.) [7], squash (Cucurbita spp.) [8], red pepper (Capsicum annuum L.) [9] and snapdragon (Antirrhinum majus L.) [10] seedlings. Research on red to far-red ratio manipulation showed effects on growth and photomorphogenesis including stem development in many plant species, such as soybean (Glycine max (L.) Merr.) [12], cucumber (Cucumis sativus L.) [13], bottle gourd (Lagenaria siceraria) [14], common bean (Phaseolus vulgaris L.) [15] and red pepper [9] seedlings
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