Effect of Duration of LED Lighting on Growth, Photosynthesis and Respiration in Lettuce

Application of ultraviolet a led as a disinfectant and morphological effects on indoor grown lettuce

Lettuce (Lactuca sativa 'Parris Island'), commonly grown in vertical farms for sustainable production, has been studied for its response to UVA LED light, but its disinfectant potential remains unexplored. Hence, the proposal intends to cover two important aspects, the development of the plant and its disinfection during cultivation, to obtain plants that are ready for consumption. Three LED light treatments were configured: Mode 1 (WBUVA-P) and Mode 2 (WBUVA-C) used White + Blue + UVA (395 nm), with intermittent and continuous application, respectively. The Control applied White + Blue (WB), denoted as Mode 3. A specific evaluation of different parameters, such as disinfection and identification of bacteria, biomass, chlorophyll content (SPAD units), and leaf area (LA), was conducted in the experiment. The most effective results were obtained with Mode 1 (WBUVA-P), achieving a 99.90% disinfection rate and promoting organic matter accumulation, as shown by increased leaf area, fresh weight, and dry weight. In contrast, Mode 2 (WBUVA-C) reached a 99.00% disinfection rate but did not significantly impact organic matter compared to the Control. These results suggest that UVA-LED radiation can be a valuable tool for food production, enhancing disinfection and organic matter content. However, further studies are needed to explore different intermittent UVA-LED emission durations and test other wavelengths.

Red-Leafed Lettuces: Genetic Variation or Epigenetic Photomorphogenesis?

Red-leaf lettuces, rich in bioactive compounds like anthocyanins and flavonoids, offer health benefits by reducing oxidative stress and boosting immunity. This article provides an extensive review of the genetic, epigenetic, environmental, and technological factors influencing anthocyanin biosynthesis and leaf coloration in red-leaf lettuce, emphasizing its significance in agriculture and nutrition. The genetics of anthocyanin biosynthesis, environmental influences, practical applications, agronomic insights, and future directions are the main areas covered. Anthocyanin accumulation is regulated by structural, regulatory, and transporter genes, as well as the MYB-bHLH-WD40 (MBW) complex. Mutations in these genes impact coloration and stress responses. Advances in genomic studies, such as GWAS and QTL mapping, have identified key genes and pathways involved in anthocyanin biosynthesis, aiding breeding programs for desirable traits. In addition, light intensity, stress conditions (e.g., drought, temperature), and phytohormones affect anthocyanin levels and photomorphogenesis in general. Controlled environments, like vertical farms, optimize these conditions to enhance pigmentation and phytochemical content. LED lighting and tailored cultivation techniques improve color intensity, antioxidant capacity, and yield in controlled settings. Sustainable production technologies for red-leaf lettuce in vertical farms are being developed to meet consumer demand and promote functional foods, integrating genetic, epigenetic, and environmental research into agronomy. This review highlights red-leaf lettuce's aesthetic, nutritional, and functional value, advocating for innovative cultivation methods to enhance its market and health potential.

Optimal Light Intensity for Lettuce Growth, Quality, and Photosynthesis in Plant Factories

In agriculture, one of the most crucial elements for sustained plant production is light. Artificial lighting can meet the specific light requirements of various plants. However, it is a challenge to find optimal lighting schemes that can facilitate a balance of plant growth and nutritional qualities. In this study, we experimented with the light intensity required for plant growth and nutrient elements. We designed three light intensity treatments, 180 μmol m-2 s-1 (L1), 210 μmol m-2 s-1 (L2), and 240 μmol m-2 s-1 (L3), to investigate the effect of light intensity on lettuce growth and quality. It can be clearly seen from the radar charts that L2 significantly affected the plant height, fresh weight, dry weight, and leaf area. L3 mainly affected the canopy diameter and root shoot ratio. The effect of L1 on lettuce phenotype was not significant compared with that of the others. The total soluble sugar, vitamin C, nitrate, and free amino acid in lettuce showed more significant increases under the L2 treatment than under the other treatments. In addition, the transpiration rate and stomatal conductance were opposite to each other. The comprehensive evaluation of the membership function value method and heatmap analysis showed that lettuce had the highest membership function value in L2 light intensity conditions, indicating that the lettuce grown under this light intensity could obtain higher yield and better quality. This study provides a new insight into finding the best environmental factors to balance plant nutrition and growth.

Integration of IoT in Small-Scale Aquaponics to Enhance Efficiency and Profitability: A Systematic Review

Aquaponics combines aquaculture and hydroponics to offer a sustainable approach to agriculture, addressing food security issues with minimal environmental harm. However, small-scale practitioners face challenges due to a lack of professional knowledge in water chemistry and system maintenance. Economic hurdles, such as operational costs and energy-intensive components, hinder the viability of small-scale aquaponics. Selecting suitable fish and plant species, along with appropriate stocking densities, is crucial. Media Bed (MB), Deep Water Culture (DWC), and the Nutrient Film Technique (NFT) are commonly used hydroponic techniques. This study outlines optimal conditions, including water quality, temperature, pH, and nutrient concentrations, essential for symbiotic fish and plant cultivation. Integrating IoT technology enhances efficiency and profitability by optimizing resource utilization, monitoring water quality, and ensuring optimal growth conditions. Knowledge sharing among practitioners fosters innovation and sustainability through collaborative learning and best practices exchange. Establishing a community for knowledge sharing is vital for continuous improvement, advancing small-scale aquaponics towards a more efficient and sustainable future.

Transcriptomic Insights into Molecular Response of Butter Lettuce to Different Light Wavelengths

Lettuce is a widely consumed leafy vegetable; it became popular due to its enhanced nutritional content. Recently, lettuce is also regarded as one of the model plants for vegetable production in plant factories. Light and nutrients are essential environmental factors that affect lettuce growth and morphology. To evaluate the impact of light spectra on lettuce, butter lettuce was grown under the light wavelengths of 460, 525, and 660 nm, along with white light as the control. Plant morphology, physiology, nutritional content, and transcriptomic analyses were performed to study the light response mechanisms. The results showed that the leaf fresh weight and length/width were higher when grown at 460 nm and lower when grown at 525 nm compared to the control treatment. When exposed to 460 nm light, the sugar, crude fiber, mineral, and vitamin concentrations were favorably altered; however, these levels decreased when exposed to light with a wavelength of 525 nm. The transcriptomic analysis showed that co-factor and vitamin metabolism- and secondary metabolism-related genes were specifically induced by 460 nm light exposure. Furthermore, the pathway enrichment analysis found that flavonoid biosynthesis- and vitamin B6 metabolism-related genes were significantly upregulated in response to 460 nm light exposure. Additional experiments demonstrated that the vitamin B6 and B2 content was significantly higher in leaves exposed to 460 nm light than those grown under the other conditions. Our findings suggested that the addition of 460 nm light could improve lettuce's biomass and nutritional value and help us to further understand how the light spectrum can be tuned as needed for lettuce production.

Spectral composition of LED light differentially affects biomass, photosynthesis, nutrient profile, and foliar nitrate accumulation of lettuce grown under various replacement methods of nutrient solution

To enhance crop yield and quality, plant cultivation in controlled-growing systems is an alternative to traditional open-field farming. The use of light-emitting diode (LED) as an adjustable light source represents a promising approach to improve plant growth, metabolism, and function. The objective of this study was to assess the impact of different light spectra (red, red/blue (3:1), blue, and white) with an emission peak of around 656, 656, 450, and 449 nm, respectively, under various replacement methods of nutrient solution (complete replacement (CR), EC-based replacement (ECBR), and replacing based on plant needs (RBPN)), on biomass, physiological traits, and macro- and micronutrient contents of two best-known lettuce varieties, Lollo Rossa (LR) and Lollo Bionda (LB), in the nutrient film technique (NFT) hydroponic system. The results indicated that mix of red and blue LED spectra under RBPN method is the most effective treatment to enhance fresh and dry weights of lettuce plants. In addition, red LED spectrum under RBPN, and red and blue light under ECBR nutrient solution significantly increased leaf stomatal conductance, net photosynthesis and transpiration rate, and intercellular CO2 concentration of LR variety. Phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mn) content in LR variety, and iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) content in both varieties increased upon exposure to blue and red LED light spectrum with RBPN method. Our results suggest that exposure to combination of red and blue light along with feeding plants using RBPN and ECBR methods can increase absorption of macro- and micronutrient elements and improve photosynthetic properties, and eventually increase lettuce yield with lower nitrate accumulation.

Effects of Light Intensity on Growth and Quality of Lettuce and Spinach Cultivars in a Plant Factory

The decreased quality of leafy vegetables and tipburn caused by inappropriate light intensity are serious problems faced in plant factories, greatly reducing the economic benefits. The purpose of this study was to comprehensively understand the impact of light intensity on the growth and quality of different crops and to develop precise lighting schemes for specific cultivars. Two lettuce (Lactuca sativa L.) cultivars-Crunchy and Deangelia-and one spinach (Spinacia oleracea L.) cultivar-Shawen-were grown in a plant factory using a light-emitting diode (LED) under intensities of 300, 240, 180, and 120 μmol m-2 s-1, respectively. Cultivation in a solar greenhouse using only natural light (NL) served as the control. The plant height, number of leaves, and leaf width exhibited the highest values under a light intensity of 300 μmol m-2 s-1 for Crunchy. The plant width and leaf length of Deangelia exhibited the smallest values under a light intensity of 300 μmol m-2 s-1. The fresh weight of shoot and root, soluble sugar, soluble protein, and ascorbic acid contents in the three cultivars increased with the increasing light intensity. However, tipburn was observed in Crunchy under 300 μmol m-2 s-1 light intensity, and in Deangelia under both 300 and 240 μmol m-2 s-1 light intensities. Shawen spinach exhibited leaf curling under all four light intensities. The light intensities of 240 and 180 μmol m-2 s-1 were observed to be the most optimum for Crunchy and Deangelia (semi-heading lettuce variety), respectively, which would exhibit relative balance growth and morphogenesis. The lack of healthy leaves in Shawen spinach under all light intensities indicated the need to comprehensively optimize cultivation for Shawen in plant factories to achieve successful cultivation. The results indicated that light intensity is an important factor and should be optimized for specific crop species and cultivars to achieve healthy growth in plant factories.

Development of Modified Farquhar-von Caemmerer-Berry Model Describing Photodamage of Photosynthetic Electron Transport in C3 Plants under Different Temperatures

Photodamage of photosynthetic electron transport is a key mechanism of disruption of photosynthesis in plants under action of stressors. This means that investigation of photodamage is an important task for basic and applied investigations. However, its complex mechanisms restrict using experimental methods of investigation for this process; the development of mathematical models of photodamage and model-based analysis can be used for overcoming these restrictions. In the current work, we developed the modified Farquhar-von Caemmerer-Berry model which describes photodamage of photosynthetic electron transport in C3 plants. This model was parameterized on the basis of experimental results (using an example of pea plants). Analysis of the model showed that combined inactivation of linear electron flow and Rubisco could induce both increasing and decreasing photodamage at different magnitudes of inactivation of these processes. Simulation of photodamage under different temperatures and light intensities showed that simulated temperature dependences could be multi-phase; particularly, paradoxical increases in the thermal tolerance of photosynthetic electron transport could be observed under high temperatures (37-42 °C). Finally, it was shown that changes in temperature optimums of linear electron flow and Rubisco could modify temperature dependences of the final activity of photosynthetic electron transport under photodamage induction; however, these changes mainly stimulated its photodamage. Thus, our work provides a new theoretical tool for investigation of photodamage of photosynthetic processes in C3 plants and shows that this photodamage can be intricately dependent on parameters of changes in activities of linear electron flow and Rubisco including changes induced by temperature.

Effects of sulfate on the photosynthetic physiology characteristics of Hydrocotyle vulgaris under zinc stress

The effects of sulfate on the zinc (Zn) bioaccumulation characteristics and photophysiological mechanisms of the ornamental plant Hydrocotyle vulgaris were explored using a hydroponic culture under three Zn concentrations (300, 500 and 700mgL-1 ) with (400μmolL-1 ) or without the addition of sulfate. Results showed that: (1) tissue Zn concentrations and total Zn contents increased with increasing hydroponic culture Zn concentrations; and sulfate addition decreased Zn uptake and translocation from roots to shoots; (2) Zn exposure decreased photosynthetic pigment synthesis, while sulfate changed this phenomenon, especially for chlorophyll a under 300mgL-1 Zn treatment; (3) Zn exposure decreased photosynthetic function, while sulfate had positive effects, especially on the photosynthetic rate (Pn ) and stomatal conductance (Gs ); and (4) chlorophyll fluorescence parameters related to light energy capture, transfer and assimilation were generally downregulated under Zn stress, while sulfate had a positive effect on these processes. Furthermore, compared to photosynthetic pigment synthesis and photosynthesis, chlorophyll fluorescence was more responsive, especially under 300mgL-1 Zn treatment with sulfate addition. In general, Zn stress affected photophysiological processes at different levels, while sulfate decreased Zn uptake, translocation, and bioaccumulation and showed a positive function in alleviating Zn stress, ultimately resulting in plant growth promotion. All of these results provide a theoretical reference for combining H. vulgaris with sulfate application in the bioremediation of Zn-contaminated environments at the photophysiological level.