UV LEDs in horticulture: from biology to application

Wargent, Jason J.

doi:10.17660/actahortic.2016.1134.4

Cited by 18 publications

(11 citation statements)

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“…For example, in comparison with the LED treatments, fluorescent light had higher R:FR (14.9 vs. #1.1), presence of ultraviolet-A and ultraviolet-B, higher G photon flux, lower R photon flux, and a correspondingly higher B: R (2:3 vs. 2:5) as the B photon flux and percent B of PPF were similar for all treatments (Table 1). A higher R:FR, higher blue (relative or absolute amount), and presence of ultraviolet have been implicated in the inhibition of stem elongation (Cope and Bugbee, 2013;Fletcher et al, 2005; Hern andez and Kubota, 2016;Wargent, 2016).…”

Section: Discussionmentioning

confidence: 99%

Morphology and Flowering Responses of Four Bedding Plant Species to a Range of Red to Far Red Ratios

Mah

Llewellyn

Zheng

2018

horts

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In greenhouse ornamental crop production, bedding plants grown below high densities of hanging baskets (HBs) tend to be of lower quality. Hanging basket crops can decrease the red to far red ratio (R:FR) of the growing environment below; however, the extent to which decreased R:FR affects plant morphology and flowering of the lower-level crops is unknown. The present study examined effects of R:FR on morphology and flowering of marigold ‘Antigua Orange’ (Tagetes erecta), petunia ‘Duvet Red’ (Petunia ×hybrida), calibrachoa ‘Kabloom Deep Blue’ (Calibrachoa ×hybrida), and geranium ‘Pinto Premium Salmon’ (Pelargonium ×hortorum). Five R:FR light treatments were provided ranging from R:FR 1.1 (representing unfiltered sunlight) to R:FR 0.7 (representing shaded conditions under HBs) using light-emitting diodes (LEDs) in growth chambers, each with identical photosynthetically active radiation (PAR) (400–700 nm) and FR added to achieve the target R:FR ratio. Two experiments using the same R:FR treatments were conducted with day/night temperature regimes of 20 °C/18 °C and 25 °C/21 °C, respectively. In the second experiment, a fluorescent light treatment was included. The results of the second experiment were more dramatic than the first, where reducing R:FR from 1.1 to 0.7 increased height by 11%, 22%, and 32% in marigold, petunia, and calibrachoa, respectively, and increased petiole length in geranium by 10%. Compared with R:FR 1.1, the R:FR 0.7 shortened the time to the appearance of first flower bud by 2 days in marigold, whereas flowering was minimally affected in other species. Compared with pooled data from the LED treatments, fluorescent light increased relative chlorophyll content for all species, reduced height in marigold, petunia, calibrachoa, and geranium by 26%, 67%, 60%, and 48%, and reduced stem dry weight by 28%, 39%, 21%, and 31%, respectively. The differences in morphology observed under fluorescent light compared with LED R:FR treatments indicate that light quality manipulation is a potential alternative to chemical growth regulators in controlled environments such as greenhouses and growth chambers.

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Section: Discussionmentioning

confidence: 99%

Morphology and Flowering Responses of Four Bedding Plant Species to a Range of Red to Far Red Ratios

Mah

Llewellyn

Zheng

2018

horts

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“…However, crops cultivated in indoor CEA systems using artificial lighting are not exposed to ultraviolet radiation. Ultraviolet (UV) radiation is an important environmental signal that initiates plant responses in photosynthetic function, cell division, plant growth, and development [3,4]. In previous studies, UV-B radiation was mainly considered as a stress factor to plants, focusing on the effects of increasing solar UV-B radiation reaching Earth's surface due to stratospheric ozone depletion [5,6].…”

Section: Introductionmentioning

confidence: 99%

Pre-Harvest UV-B Radiation and Photosynthetic Photon Flux Density Interactively Affect Plant Photosynthesis, Growth, and Secondary Metabolites Accumulation in Basil (Ocimum basilicum) Plants

Dou

Niu

Gu³

2019

Agronomy

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Phenolic compounds in basil (Ocimum basilicum) plants grown under a controlled environment are reduced due to the absence of ultraviolet (UV) radiation and low photosynthetic photon flux density (PPFD). To characterize the optimal UV-B radiation dose and PPFD for enhancing the synthesis of phenolic compounds in basil plants without yield reduction, green and purple basil plants grown at two PPFDs, 160 and 224 μmol·m−2·s−1, were treated with five UV-B radiation doses including control, 1 h·d−1 for 2 days, 2 h·d−1 for 2 days, 1 h·d−1 for 5 days, and 2 h·d−1 for 5 days. Supplemental UV-B radiation suppressed plant growth and resulted in reduced plant yield, while high PPFD increased plant yield. Shoot fresh weight in green and purple basil plants was 12%–51% and 6%–44% lower, respectively, after UV-B treatments compared to control. Concentrations of anthocyanin, phenolics, and flavonoids in green basil leaves increased under all UV-B treatments by 9%–18%, 28%–126%, and 80%–169%, respectively, and the increase was greater under low PPFD compared to high PPFD. In purple basil plants, concentrations of phenolics and flavonoids increased after 2 h·d−1 UV-B treatments. Among all treatments, 1 h·d−1 for 2 days UV-B radiation under PPFD of 224 μmol·m−2·s−1 was the optimal condition for green basil production under a controlled environment.

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“…Moreover, UV LEDs have lower photon efficiency than other visible spectrum LEDs. Consequently, the usage of UV wavelengths in CEA is still in its initial stages (Wargent, 2016; Neugart and Schreiner, 2018). Although UV LED lighting is a new technology, research has been conducted on the effects of UV-A LED, as a part of different lighting systems or as a sole source of light, on the growth and metabolism of plants (Li and Kubota, 2009; Samuolienė et al, 2013; Khoshimkhujaev et al, 2014; Brazaitytė et al, 2015; Vaštakaitė et al, 2015; Lee et al, 2014; Brazaitytė et al, 2016; Goto et al, 2016; Rechner et al, 2017; Jensen et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Response of Mustard Microgreens to Different Wavelengths and Durations of UV-A LEDs

et al. 2019

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Ultraviolet A (UV-A) light-emitting diodes (LEDs) could serve as an effective tool for improving the content of health-promoting bioactive compounds in plants in controlled-environment agriculture (CEA) systems. The goal of this study was to investigate the effects of UV-A LEDs at different wavelengths (366, 390, and 402 nm) and durations (10 and 16 h) on the growth and phytochemical contents of mustard microgreens (Brassica juncea L. cv. “Red Lion”), when used as supplemental light to the main LED lighting system (with peak wavelengths of 447, 638, 665, and 731 nm). Plants were grown for 10 days under a total photon flux density (TPFD) of 300 µmol m−2 s−1 and 16-h light/8-h dark period. Different UV-A wavelengths and irradiance durations had varied effects on mustard microgreens. Supplemental UV-A radiation did not affect biomass accumulation; however, the longest UV-A wavelength (402 nm) increased the leaf area of mustard microgreens, regardless of the duration of irradiance. The concentration of the total phenolic content and α-tocopherol mostly increased under 402-nm UV-A, while that of nitrates increased under 366- and 390-nm UV-A at both radiance durations. The contents of lutein/zeaxanthin and β-carotene increased in response to the shortest UV-A wavelength (366 nm) at 10-h irradiance as well as longer UV-A wavelength (390 nm) at 16 h irradiance. The most positive effect on the accumulation of mineral elements, except iron, was observed under longer UV-A wavelengths at 16-h irradiance. Overall, these results suggest that properly composed UV-A LED parameters in LED lighting systems could improve the nutritional quality of mustard microgreens, without causing any adverse effects on plant growth.

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UV LEDs in horticulture: from biology to application

Cited by 18 publications

References 50 publications

Morphology and Flowering Responses of Four Bedding Plant Species to a Range of Red to Far Red Ratios

Morphology and Flowering Responses of Four Bedding Plant Species to a Range of Red to Far Red Ratios

Pre-Harvest UV-B Radiation and Photosynthetic Photon Flux Density Interactively Affect Plant Photosynthesis, Growth, and Secondary Metabolites Accumulation in Basil (Ocimum basilicum) Plants

Response of Mustard Microgreens to Different Wavelengths and Durations of UV-A LEDs

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