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Open AccessArticle

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

1
Department of Horticultural Sciences, Texas A&M University, College Station, TX 77843, USA
2
Department of Horticultural Sciences, Texas A&M AgriLife Research & Extension, The Dallas Center, Texas A&M University, 17360 Coit Road, Dallas, TX 75252, USA
3
Department of Horticultural Sciences, Texas A&M AgriLife Extension Service, College Station, TX 77843, USA
*
Author to whom correspondence should be addressed.
Agronomy 2019, 9(8), 434; https://doi.org/10.3390/agronomy9080434
Received: 19 July 2019 / Revised: 5 August 2019 / Accepted: 5 August 2019 / Published: 7 August 2019
(This article belongs to the Special Issue Soilless Culture, Growing Media and Horticultural Plants)
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. View Full-Text
Keywords: UVR8; PPFD; dose-dependent; photosynthesis; chlorophyll fluorescence; phenolic compounds UVR8; PPFD; dose-dependent; photosynthesis; chlorophyll fluorescence; phenolic compounds
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Dou, H.; Niu, G.; Gu, M. Pre-Harvest UV-B Radiation and Photosynthetic Photon Flux Density Interactively Affect Plant Photosynthesis, Growth, and Secondary Metabolites Accumulation in Basil (Ocimum basilicum) Plants. Agronomy 2019, 9, 434.

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