The Mechanisms of Different Light Supply Patterns in the Nutrient Uptake and Chlorophyll Fluorescence of Hydroponic Lettuce

• Published in: Agronomy (Basel) 2023-07, Vol.13 (7), p.1910
• Main Authors: Liu, Yanwei, Cao, Ni, Shi, Xiaolan, Meng, Fei, Zhou, Yingjie, Wang, Haidong, Yang, Qiliang
• Format: Article
• Language: English
• Subjects: Absorption; Carbon dioxide; Carbon dioxide concentration; Chlorophyll; chlorophyll fluorescence; Circadian rhythm; Circadian rhythms; Crop yield; Electron transport; Electron transport chain; Energy consumption; Excitons; Factories; Fluctuations; Fluorescence; Hydroponics; lettuce; Light sources; light supply mode; Manganese; nutrient absorption; Nutrient content; Nutrient uptake; Photochemical reactions; Photochemicals; Photosynthesis; Pigments; plant factory; Plants (botany); Quality assurance; Stomata; Transpiration; Vegetables; Vertical farming
• ISSN: 2073-4395; 2073-4395
• DOI: 10.3390/agronomy13071910

Vertical agriculture has developed rapidly in recent years, pushing artificial light planting to new heights. Under indoor artificial light, the light supply mode has practical significance in studying the impact of lighting conditions on plants. This experiment involved five intermittent light supply modes (with a light period of 16 h and a dark period of 8 h (16/8) as the control group, with a light period of 8 h and a dark period of 4 h repeated twice a day (8/4), a light period of 4 h and a dark period of 2 h repeated four times a day (4/2), a light period of 2 h and a dark period of 1 h repeated eight times a day (2/1), and a light period of 1 h and a dark period of 0.5 h repeated 16 times a day (1/0.5) (as the experimental groups). A total of ten treatments were combined before the continuous light supply mode (B) and after the continuous light supply mode (A). Through experimental settings, we explored the response mechanisms to intermittent and continuous light supply modes as they pertain to lettuce growth, nutrient content, photosynthetic parameters, and light stress. Through research, it was found that continuous light supply significantly increased plant height, root length, aboveground dry and fresh weight, and the underground dry and fresh weight of lettuce. The treatments with a light period 4 h/dark period 2 h (4/2) and a light period 8 h/dark period 4 h (8/4) significantly increased the N, P, K, and Cu contents. Additionally, continuous light supply helped stabilize the Mg, Ca, and Mn contents across all treatment groups. Stomatal closure has been found to cause a decrease in the rate of net photosynthesis, transpiration, and intercellular CO2 concentration. The energy absorbed by antenna pigments is significantly increased when participating in photochemical reactions; however, continuous light supply has been observed to reduce the absorption flux per reaction center (ABS/RC), trapped energy flux per reaction center (TR0/RC), electron transport flux per reaction center (ET0/RC), and the probability that a trapped exciton moves an electron into the electron transport chain beyond QA− (at t = 0) (ET0/TR0). Conversely, the electron transport flux per cross section (ET0/CS) has been found to increase significantly. In summary, among the intermittent light supply treatment groups, the 2/1 treatment group showed the best response to growth indicators, nutrient absorption, and photosynthesis, and could improve the quality of lettuce without add