Supplemental Daily Light Integrals Influence Carotenoid Concentrations in Hydroponically Grown Genovese Pesto Basil
Hammock, H. A., D. A. Kopsell, and C. E. Sams.  2018.  HortScience, 53(9):S492. This Poster won First Plast in the SRASHS Graduate Student Poster Competition.

Plants have the ability to respond to a wide range of intensities and narrowband wavelengths from the solar spectrum. While many studies have shown that light emitting diode (LED) supplementation is useful for high-value specialty crop production, research is needed to determine the value and efficacy of LEDs in comparison to traditional lighting systems, with emphasis placed on determining the impact of spectral distribution and daily light integral (DLI) on secondary metabolism. The objective of this study was to establish the effects of progressive DLI on the production of carotenoid and chlorophyll pigments in hydroponic basil (Ocimum basilicum var. ‘Genovese’) using LED and high-pressure sodium (HPS) lighting sources. A total of nine lighting treatments were used: one non-supplemented natural light control, two HPS treatments with DLIs as 12 h and 24 h, and six 20B/80R LED treatments with progressive DLIs as 3 h, 6 h, 9 h, 12 h, 18 h, and 24 h. Each supplemental lighting treatment provided 100 µmols.m-2.sec-1. The DLI of the natural light control averaged 9.9 mol.m-2.d-1 during the growth period (ranging from 4 to 20 mol.m-2.d-1). Relative humidity averaged 50%, with day/night temperatures averaging 29.4 °C/23.8 °C, respectively. Basil plants were harvested 45 d after seeding, and leaf tissue pigments were analyzed using HPLC (Agilent 1200 Series). Concentrations of lutein, â-carotene, chlorophyll a, chlorophyll b, antheraxanthin and zeaxanthin varied among DLI supplements and natural light controls. Xanthophyll cycle flux ratios were significantly impacted by DLI supplement and lighting type. Further research should be conducted to establish the relationship between specific DLI supplements and the biosynthesis of nutritionally important carotenoids. Because LEDs have the potential to improve antioxidant concentrations in many high-value specialty crops, various herb varieties should also be evaluated to determine the biochemical and physiological impacts of LED supplemental lighting.