Effects of red/blue versus white LED light of different intensities on the growth and organic carbon and autotoxin secretion of hydroponic lettuce

• Published in: Horticulture, environment and biotechnology 2022, Environment, and Biotechnology, 63(2), , pp.195-205
• Main Authors: Zhou, Chengbo, Wang, Qi, Liu, Wenke, Li, Baoshi, Shao, Mingjie, Zhang, Yubin
• Format: Article
• Language: English
• Subjects: Acids; Agriculture; Benzoic acid; Biomedical and Life Sciences; Carbon; Dry weight; Exudates; Exudation; Factories; Ferulic acid; Gallic acid; Hydroponics; Industrial plants; Lettuce; Life Sciences; Light; Light intensity; Luminous intensity; Metabolism; Nutrient content; Nutrient utilization; Organic carbon; Photosynthesis; Plant Breeding/Biotechnology; Plant Ecology; Plant growth; Plant Physiology; Research Report; Secretion; Surface area; Tannic acid; Total organic carbon; Vegetables; White light; 농학
• ISSN: 2211-3452; 2211-3460
• DOI: 10.1007/s13580-021-00394-3

Light is a crucial signal for plant growth, development, and secondary metabolism. Exploring the effects of light on autotoxin secretion in lettuce can be helpful for improving the utilization efficiency of the nutrient solution in plant factories. The effects of white light (WL) and the combination of red (R) and blue (B) light (RB, 4R:1B) at different intensities (150, 200, and 250 μmol m −2  s −1 ) on the growth and root exudates of hydroponic lettuce ( Lactuca sativa L.) were studied in a closed plant factory. The lettuce biomass and photosynthetic rate increased with the increasing light intensity, and the photosynthetic rate was significantly lower under WL than under RB at both 200 and 250 μmol m −2  s −1 . Lettuce under WL had the longest root length and highest root surface area at 200 μmol m −2  s −1 , while the root length, root surface area, and root volume under RB were the highest at 250 μmol m −2  s −1 . Total organic carbon (TOC) content of root exudates in the nutrient solution based on shoot or root dry weight decreased with the increasing light intensity. With the increase in light intensity, the secretion of four autotoxins (benzoic acid, ferulic acid, gallic acid, and tannic acid) based on shoot dry weight and root dry weight decreased under WL. Compared with RB, WL significantly reduced the secretion of autotoxins at 250 μmol m −2  s −1 . In conclusion, 250 μmol m −2  s −1 white light should be used for high lettuce yield, and it could also decrease the autotoxins in the nutrient solution and the occurrence of autotoxicity.