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Light intensity and nitrogen concentration in nutrient solutions are two main factors affecting the growth and nutritional quality of lettuce(Lactuca sativa L.). This study investigated the method of regulating vegetable cultivation through the interactive control of the light environment and solution ratio. A quadratic regression orthogonal model was developed to understand the role of light intensity (43 to 237 µmol m−2s−1) and nitrogen concentration (4.3 to 23.7 mmol L−1) in lettuce growth. Dry weight, vitamin C, and nitrate contents were measured and modelled to understand the coupling effect of light intensity and nitrogen concentration on lettuce. The optimised conditions for lettuce growth were 237 µmol m−2 s−1 of light intensity and 9.2 mmol L−1 of nitrogen concentration, and these conditions were predicted to produce lettuce with an average dry biomass of 3.9 g plant−1, 149.9 µg g−1 of Vitamin C, and 212.1 µg g−1 of nitrate content based on their respective weighting factors (0.50, 0.25, and 0.25). The lettuce yield and quality were verified using the modelled optimised growth conditions and the lettuce grown was indeed more nutritional compared to the commercially available lettuce. The findings are important for mass production of lettuce in plant factories and greenhouses. [ABSTRACT FROM AUTHOR]

Spectral composition of artificial light is an important environmental factor for plants cultivated in controllable environment, eg., plant factory. In an attempt to explore the influence of different spectral wavebands on leaf lettuce growth and development, a new way of light treatment with turning off the specific narrow-wavebands from the wide spectrum was established. And leaf lettuce was cultivated under different light spectra with the spectral wavebands of green (LG), yellow (LY) and purple (LP) “knockout” respectively in controllable environment. Then changes in biomass, morphological indexes, photosynthetic gas exchange, chlorophyll content and soluble sugar content of lettuce were examined. Our results revealed that, compared with plants grown under wide-spectral LED light (CK), LG treatment showed significantly reduction of fresh shoot weight at 25 days after planting (DAP) comparing to CK. LY and LP obtained obviously higher fresh shoot weight and moisture content at 15 DAP, in contrast, significantly lower ratio of root to shoot than CK. And A/Ci in LG were significantly reduced by about 33.3% and 36.1% at 20 DAP and 25 DAP respectively compared with CK. In addition, LY showed significant increases in soluble sugar content compared to other treatments at three sampling stages, while the lowest values were obtained in CK. These results indicated that green, yellow and purple light had significant regulations on the biomass, photosynthesis and soluble sugar content in lettuce, depending on the different growth period. [ABSTRACT FROM AUTHOR]

Light-emitting diodes (LEDs) hold great potential as electric light source for leafy vegetable production in controlled environment. However, most of LED lights in vegetable cultivation were only combined with red and blue LEDs, and the spectral composition was oversample. Previous studies reported that light spectral composition could influence nutritional quality of vegetables, e.g., nitrate content. In order to better understand the influence of spectral composition on nitrate accumulation of leafy vegetables grown in closed-type system. The nitrate content, nitrate primary metabolism of 35-day-old lettuce (Lactuca sativa L. Var. youmaicai) in vivo and its biomass were investigated. The results showed that cool white fluorescent light (T5) and high-pressure sodium light (HPS) with wide spectrum significantly reduced nitrate content in lettuce than red and blue combination LED light (RB-LED) treatment. Our findings demonstrated that a proper optimizing procedure of light spectrum with supplemental other wavebands in RB-LEDs is necessary for reducing nitrate accumulation of lettuce. [ABSTRACT FROM AUTHOR]

Abstract: To establish bioregenerative life support system (BLSS) on lunar or Mars bases in the future, it is necessary to firstly conduct manned simulation experiments, including several different kinds of creatures on the ground. To provide the basis for establishing the system, a multibiological life support system composed of lettuce, silkworm and algae was set up in this study. Lettuce and silkworms were cultivated in a closed integrated cultivating system (CICS) of integrative experimental system (IES). The conveyor-type cultivation method was implemented, which harvested the largest batch of lettuce and silkworms from the system and carried the smallest batch of them into the system every four days. During this process, the main element contents of lettuce were determined. Biomasses, heights, and crown diameters of lettuce in and out of the system were compared. Biomasses, excrement production rates, and bioconversion rates of silkworms in and out of the system were also studied. Results showed silkworms and lettuce in the IES could grow normally. There were no significant differences of biomass, height, or excrement production rates between creatures (lettuce and silkworms) in the system and those out of the system. [Copyright &y& Elsevier]

Abstract: To establish bioregenerative life support systems (BLSS) on lunar or mars bases, firstly, it is necessary to conduct BLSS experiments including humans and various kinds of creatures on the ground. Carbon and nitrogen balances as well as water cycle are the important subjects that need to be studied. To provide basis for establishing a manned BLSS, a multibiological life support system composed of lettuce, silkworm and algae was set up in this study to carry out gas exchange investigation between humans and the system. During this process, the production rate and quality of condensate, substance flows of lettuce, silkworm and algae in and out of the system as well as carbon and nitrogen contents of these substances were studied. Results showed water was completely cycled in the system and condensate quality was relatively good, certain amounts of carbon and nitrogen were accumulated in the system and existed in the form of microorganisms. [Copyright &y& Elsevier]

Abstract: To establish a Bioregenerative Life Support System (BLSS) in lunar or Mars bases in the future, manned stimulation experiments including several kinds of creatures are needed to be conducted first. Gas exchange relation, element transfer and transformation principles, etc. between humans and the multibiological system composed of plants, animals, microalgae and so on must be investigated in order to place different organisms with appropriate numbers and proportions in the BLSS. This research cultivated lettuce (Lactuca sativa L.) and silkworm (Bombyx mori L.) in the CICS (Closed Integrative Cultivating System) of the IES (Integrative Experimental System) with Chlorella vulgaris cultivated in the PPB (Plate Photo Bioreactor) of the IES. Conveyor-type cultivation method was implemented for harvesting the largest batch of lettuce and silkworms through the mass exchange chamber of the IES every four days and transferring the smallest batch of lettuce and silkworms into the system; carrying certain amounts of alga liquid out with nutrient liquid replenished every day. Gas exchange between testers and the IES including three phases was conducted periodically. Phase I involved one person participating in gas exchange with lettuce in plant chamber as primary means of air revitalization for 3 months. Phase II was gas exchange between one person and autotrophic creatures, which were lettuce and microalgae, for 1 month. In the Phase III test, silkworms were introduced into the animal chamber for 2 months. Mathematical modeling and experimental simulation for this system was done to study its gas robustness. Results show that CO2/O2 concentration fluctuated around normal levels, the system possessed relatively good gas robustness and there were no trace gas (CH4, NH3 and C2H4) contaminant problems in the system. [Copyright &y& Elsevier]