Optimization of Artificial Light for Spinach Growth in Plant Factory Based on Orthogonal Test

Abstract

Artificial LED source provides the possibility to regulate the lighting environment in plant factorys that use limited space to plant, aiming at high throughput and good quality. However, different parameters of light intensity, quality, and photoperiod will influence the growth and accumulation of bio-compounds in plants. In order to find the optimal setting of LED light for spinach planting, four group experiments were designed using the orthogonal testing method. According to the experimental results, for growth indexes including fresh weight, dry weight, root length and so on, photoperiod is the most influential factor, light intensity is the second, and light quality is the least. The best light mode (R:B = 4:1, photosynthetic photon flux density (PPFD) = 100 μmol∙m−2∙s−1 and 13/11 h) among all eight possible combinations in the range was also determined. Furthermore, for quality indexes, including the soluble sugar content, protein content and so on, a new scoring method was introduced to make a comprehensive score for evaluating. Then, the light combination (R:B = 4:1, PPFD = 150 μmol∙m−2∙s−1 and 9/15 h) in the range was found as the optimal scheme for spinach quality under those parameters. As there is trade-off between the optimal light parameters for growth and quality, it is necessary to achieve a balance between yield and quality of the plant during production. If farmers want to harvest spinach with larger leaf area and higher yield, they need to pay attention to the adjustment of the photoperiod and use a lower light intensity and a longer lighting time. If they do not mind the yield of the vegetable but want to improve the taste and nutrition of spinach products, they should pay more attention to the light intensity and use a higher light intensity and a shorter lighting time.

Hybrid Genetic Programming and Multiverse-based Optimization of Pre-Harvest Growth Factors of Aquaponic Lettuce Based on Chlorophyll Concentration

“…The optimization results of this study showed that GA, PSO, and MVO effectively determine the best global solution for nonlinear problems such as the maximization of chlorophylla concentrations as a function of carbon dioxide, light intensity, air temperature, and humidity (Table 2). Prior studies have reported that for soilless lettuce cultivation, the acceptable threshold for carbon dioxide concentration, light intensity, temperature, and humidity is 803.019 to 1300 ppm [17], [21], ≥ 175.23 μmol m -2 s -1 [15], [17], [23], 18 to 23 °C [14], [17], [18], and 60% to 75% [14], respectively. Based on the converged best solutions of GA, the temperature is above the ideal range, and the humidity is slightly short (Table 2).…”

“…Far-red (FR) light has a positive impact on the photomorphogenesis of greenhouse plants [20], monochromatic red and blue lights result in to decrease in stomatal density [21], and red-blue and yellow spectrums affect the air temperature and humidity [22]. The combination of red-blue light (4:1) and 15 hours photoperiod has been tested effective for spinach [23]. The photoperiod of consecutive 15 light hours and 22 hours for dark-period respiration suggested an increase in photosynthetic rate as expressed by low starch content in the leaf [24].…”

Effect of LED Spectrum on the Quality and Nitrogen Metabolism of Lettuce Under Recycled Hydroponics

“…With the rapid development of greenhouse agriculture, plant factory production and greenhouse light supplementation have become key technologies in protected horticulture production. Hydroponics in plant factories offers numerous advantages, such as high yield, good quality, continuous production, efficient resource utilization, and avoidance of the impacts of environment change; it has been used to solve the unstable vegetable supply and the pollution of land resources (Viršilë et al, 2020;Zou et al, 2020). However, hydroponics production can cause the accumulation of nitrate nitrogen in plants, especially in leaf vegetables, such as lettuce (Lactuca sativa L.) (Rouphael et al, 2018).…”

Water-use efficiency and nitrogen uptake in rice seedlings grown under different light quality

“…Optimization of lighting environment is one major challenge to promote availability for plant production in green house or plant factory (Rehman et al, 2017;Zou et al, 2020). Lighting environment, including the light spectrum, intensity, and photoperiod, regulates plant morphogenesis, plant photosynthetic differentiation and growth (Hughes, 1981).…”

“…Recently, green light has also been reported to contribute to photosynthesis in plants (Smith et al, 2017). For optimization of lighting environment, light-emitting diodes (LEDs) provide light within the required narrow spectrum for plant photosynthesis, morphogenesis, and growth (Rehman et al, 2017), and allows an evaluation of the spectrum composition necessary to provide optimal plant production conditions (Zou et al, 2020). Different spectral light induces distinct morphogenetic and photosynthetic responses that vary depending on plant species and/or cultivars (Chen et al, 2014;Clavijo-Herrera et al, 2018).…”