Blue Light added with Red LEDs Enhance Growth Characteristics, Pigments Content, and Antioxidant Capacity in Lettuce, Spinach, Kale, Basil, and Sweet Pepper in a Controlled Environment

Most Tahera Naznin; Mark Lefsrud; Valerie Gravel; Md Obyedul Kalam Azad

doi:10.3390/plants8040093

Blue Light added with Red LEDs Enhance Growth Characteristics, Pigments Content, and Antioxidant Capacity in Lettuce, Spinach, Kale, Basil, and Sweet Pepper in a Controlled Environment

Plants (Basel). 2019 Apr 8;8(4):93. doi: 10.3390/plants8040093.

Authors

Most Tahera Naznin¹, Mark Lefsrud², Valerie Gravel³, Md Obyedul Kalam Azad⁴

Affiliations

¹ Department of Biosystems and Technology, Swedish University of Agricultural Sciences, 103-23053 Alnarp, Sweden. naznin.most.tahera@slu.se.
² Bioresource Engineering Department, McGill University, Ste-Anne-de-Bellevue, QC H9X3V9, Canada. mark.lefsrud@mcgill.ca.
³ Plant Science Department, McGill University, Ste-Anne-de-Bellevue, QC H9X3V9, Canada. valerie.gravel@mcgill.ca.
⁴ Department of Bio-Health Technology, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Korea. azadokalam@gmail.com.

Abstract

The aim of this study was to investigate the different combinations of red (R) and blue (B) light emitting diode (LEDs') lighting effects on growth, pigment content, and antioxidant capacity in lettuce, spinach, kale, basil, and pepper in a growth chamber. The growth chamber was equipped with R and B light percentages based on total light intensity: 83% R + 17% B; 91% R + 9% B; 95% R + 5% B; and control was 100% R. The photosynthetic photon flux density (PPFD), photoperiod, temperature, and relative humidity of the growth chamber were maintained at 200 ± 5 μmol m^-2 s^-1, 16 h, 25/21 ± 2.5 °C, and 65 ± 5%, respectively. It is observed that the plant height of lettuce, kale, and pepper was significantly increased under 100% R light, whereas the plant height of spinach and basil did not show any significant difference. The total leaf number of basil and pepper was significantly increased under the treatment of 95% R + 5% B light, while no significant difference was observed for other plant species in the same treatment. Overall, the fresh and dry mass of the studied plants was increased under 91% R + 9% B and 95% R + 5% B light treatment. The significantly higher flower and fruit numbers of pepper were observed under the 95% R + 5% B treatment. The chlorophyll a, chlorophyll b, and total chlorophyll content of lettuce, spinach, basil, and pepper was significantly increased under the 91% R + 9% B treatment while the chlorophyll content of kale was increased under the 95% R + 5% B light treatment. The total carotenoid content of lettuce and spinach was higher in the 91% R + 9% B treatment whereas the carotenoid content of kale, basil, and pepper was increased under the 83% R + 17% B treatment. The antioxidant capacity of the lettuce, spinach, and kale was increased under the 83% R + 17% B treatment while basil and pepper were increased under the 91% R + 9% B treatment. This result indicates that the addition of B light is essential with R light to enhance growth, pigment content, and antioxidant capacity of the vegetable plant in a controlled environment. Moreover, the percentage of B with R light is plant species dependent.

Keywords: antioxidant; basil; blue LED; growth; kale; lettuce; pepper; pigment; red LED; spinach.