Red Leaf Lettuce Research Articles

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.

Interaction of the Far-red Radiation Intensity and CO2 Concentration during Early Indoor Production Stages of Red Leaf Lettuce

Although far-red (FR) radiation (700–750 nm) is beyond the traditional photosynthetically active radiation (PAR) waveband (400–700 nm), recent findings suggest equivalent or similar photosynthetic action when applied along with shorter PAR wavelengths. Potential interactive effects of FR with other environmental factors that affect photosynthesis, such as CO2, have not been widely established. In the present study, the effects of four FR photon flux densities (0, 20, 40, or 60 µmol·m−2·s−1) substituting for red (R; 600–700 nm) in combination with three CO2 concentrations (400, 800, or 1200 µmol·mol−1) were investigated at three distinctive stages of young red lettuce production. We tested whether the photomorphogenic response of young plant leaves to FR would result in a higher light interception area, as well as whether interactive effects of CO2 with FR might modify the effects of FR alone. The total photon flux density (TPFD) was maintained at a low limiting intensity of 200 µmol·m−2·s−1 (daily light integral: 11.5 mol·m−2·d−1), consistent with indoor commercial setpoints for sole-source lighting. Although blue (B; 400–500 nm) was held constant at 20 µmol·m−2·s−1 for all treatments, different combinations of R and FR were adjusted. Red oakleaf lettuce (Lactuca sativa ‘Rouxai’) used as a model test crop was harvested at 14 days (small baby greens), 18 days (standard baby greens), and 22 days (teen greens) after sowing. Crop productivity was highest at 800 µmol·mol−1 CO2 for small and standard baby stages. At the teen green stage, plant productivity was similar for the two elevated CO2 concentrations. The FR substitution for R did not affect dry biomass accumulation at all CO2 concentrations tested, thus supporting equivalent photosynthetic action. A photomorphogenic effect of FR that elongated but did not increase the area of leaves persisted from the earliest to the most mature stage of crop development tested. The FR inclusion in the light recipe resulted in longer, thinner leaves with lower biomass compared to those without FR. At higher FR fluxes, purple pigmentation reduction occurred. However, the interaction of elevated CO2 with FR radiation counteracted purple pigment reduction caused by FR alone. Substitution of FR in the light recipe for indoor production of young ‘Rouxai’ lettuce at low limiting light intensity did not improve productivity, even in combination with elevated CO2.

Luminescent Quantum Dot Films Increase the Radiation Capture and Yield of Lettuce and Sweet Basil Compared to a Traditional/Neutral-density Greenhouse Glazing

Utilizing quantum dot (QD) luminescent films as a greenhouse covering material is an innovative method of modifying the greenhouse light spectrum. The QD films convert a portion of high-energy ultraviolet and blue photons to lower-energy photons. Previous research has shown that the application of QD films in greenhouses led to improved crop yields of red lettuce and tomatoes. However, the underlying mechanism of the yield increases has not been fully explored. We quantified the effects of solar spectral shifts attributable to QD films on plant morphology, radiation capture, and, subsequently, crop yield. Green and red leaf lettuces and basil were grown in a greenhouse under four treatments: regular-concentration QD film (reg QD film); high-concentration QD film (high QD film); color-neutral polyethylene (PE) film; and control treatment without any films. Compared to the reg QD film, the high QD film converted a higher fraction of blue photons into longer-wavelength photons, resulting in enhanced leaf expansion, stem elongation, and shoot fresh weight of red lettuce and basil compared with those grown under the PE film without spectral modifications. No significant growth differences were observed between the control and high QD film treatments of red lettuce and basil despite a 23% reduction in the average daily light integral (DLI) under the high QD film treatment. Compared to that grown under the control treatment, green lettuce grown under the high QD film treatment had a similar total leaf area but reduced shoot biomass; this was likely associated with reductions in leaf thickness and chlorophyll content. In contrast, the red lettuce showed more pronounced leaf expansion and reduced leaf anthocyanin content under the high QD film, which likely helped to offset the reduction in DLI. Overall, our results indicated that modifying the solar spectrum with QD films as greenhouse covering material could result in improved crop radiation capture and yield in greenhouse production of lettuce and basil. However, the spectral shifts caused by the QD films may affect crop quality attributes, such as anthocyanin levels and the production of other beneficial secondary metabolites. This effect on crop quality should be carefully considered and requires further study.

Light Environment Analysis and Production of Red Leaf Lettuce in Greenhouses with Flexible Solar Cells

Light Environment Analysis and Production of Red Leaf Lettuce in Greenhouses with Flexible Solar Cells

Raising root zone temperature improves plant productivity and metabolites in hydroponic lettuce production.

While it is commonly understood that air temperature can greatly affect the process of photosynthesis and the growth of higher plants, the impact of root zone temperature (RZT) on plant growth, metabolism, essential elements, as well as key metabolites like chlorophyll and carotenoids, remains an area that necessitates extensive research. Therefore, this study aimed to investigate the impact of raising the RZT on the growth, metabolites, elements, and proteins of red leaf lettuce. Lettuce was hydroponically grown in a plant factory with artificial light at four different air temperatures (17, 22, 27, and 30°C) and two treatments with different RZTs. The RZT was raised 3°C above the air temperature in one group, while it was not in the other group. Increasing the RZT 3°C above the air temperature improved plant growth and metabolites, including carotenoids, ascorbic acids, and chlorophyll, in all four air temperature treatments. Moreover, raising the RZT increased Mg, K, Fe, Cu, Se, Rb, amino acids, and total soluble proteins in the leaf tissue at all four air temperatures. These results showed that raising the RZT by 3°C improved plant productivity and the metabolites of the hydroponic lettuce by enhancing nutrient uptake and activating the metabolism in the roots at all four air temperatures. Overall, this research demonstrates that plant growth and metabolites can be improved simultaneously with an increased RZT relative to air temperature. This study serves as a foundation for future research on optimizing RZT in relation to air temperature. Further recommended studies include investigating the differential effects of multiple RZT variations relative to air temperature for increased optimization, examining the effects of RZT during nighttime versus daytime, and exploring the impact of stem heating. This research has the potential to make a valuable contribution to the ongoing growth and progress of the plant factory industry and fundamental advancements in root zone physiology. Overall, this research demonstrates that plant growth and metabolites can be improved simultaneously with an increased RZT relative to air temperature. This study serves as a foundation for future research on optimizing RZT in relation to air temperature. Further recommended studies include investigating the differential effects of multiple RZT variations relative to air temperature for increased optimization, examining the effects of RZT during nighttime versus daytime, and exploring the impact of stem heating. This research has the potential to make a valuable contribution to the ongoing growth and progress of the plant factory industry and fundamental advancements in root zone physiology.

Foliar Application of Humic Acid on Growth and Biomass Improvement of Bok Choy and Red Leaf Lettuce

Humic acid (HA) is an organic product that is applied as a foliar spray to stimulate the growth and health of various horticultural and agricultural crops. However, its impact on the growth, yield, and health of exotic vegetable crops such as bok choy (Brassica rapa L.) and red leaf lettuce (Lactuca sativa L.) needs to be further explored. The current study aimed to assess the impact of foliar application of HA on the growth and biomass production of bok choy and red leaf lettuce. Notably, the foliar spray of 2% HA resulted in increased plant height, leaf length and width, leaf area, and overall plant biomass production in both bok choy and red leaf lettuce compared to the control group. However, the foliar spray of HA did not significantly affect the shoot and root length, nor the number of leaves of bok choy compared to a control. Moreover, the application of HA significantly improved the shoot length and the number of leaves of red leaf lettuce compared to the control group. Hence, HA emerges as a promising natural resource for enhancing agricultural production sustainably. It could serve as a superior growth enhancer for both bok choy and red leaf lettuce.

Effect of Seed Pelleting Application of Plant Growth Promoting Bacteria on Germination and Growth of Lettuce (Lactuca sativa)

Plant growth-promoting bacteria (PGPB) are commonly used to pellet seeds. Different bacterial strains affect germination and plant growth in varying ways. The objective of this experiment was to study the effects of seed pelleting with three strains of bacteria on changes in germination, vigor, seedling growth, and the plant growth of lettuce. The experiment followed a completely randomized design with four repetitions and five treatments: without pelleting (T1), pelleting with CaSO4-zeolite only (T2), pelleting with 1×107 CFU/mL Stenotrophomonas sp. strain sk3 (T3), pelleting with 1×108 CFU/mL Burkholderia sp. strain 3-DB05 (T4), and pelleting with 1×108 CFU/mL Enterobacter sp. strain 4-RB05 (T5). Burkholderia sp. and Enterobacter sp. were more effective in producing indole-3-acetic acid (IAA), and pelleting seeds with these strains resulted in higher germination rates and seedling growth compared to unpelleted seeds when tested in both laboratory and greenhouse conditions. Seed pelleting with 1×108 CFU/mL Enterobacter sp. promoted plant growth and resulted in significantly higher leaf and root weight. Therefore, seed pelleting with 1×108 CFU/mL Enterobacter sp. strain 4-RB05 is recommended to improve the germination and plant growth of Red Oak Leaf lettuce seeds.

Sources and Doses of Phosphorus in the Production of Red-Leaf Lettuce in an Organic Farming System

Sources and Doses of Phosphorus in the Production of Red-Leaf Lettuce in an Organic Farming System

Plants Wilt Disease of Red Leaf Lettuce (Lactuca sativa L.) After Colonized by Trichoderma longibrachiatum

Trichoderma longibrachiatum rarely reported can cause disease in plants. The present study investigates the pathogenicity of T. longibrachiatum isolate UPMT14 on the red leaf lettuce (Lactuca sativa L.) plants grown in sterile soil under a controlled growth room environment. The fungal isolate was initially characterized morphologically as Trichoderma sp. and was then further characterized by (ITS) region sequencing and BLAST comparison identified as T. longibrachiatum. To observe the response of Trichoderma isolate UPMT14 when imposed on lettuce plants. The injection was made and repeated five times, and then the lettuce growth followed for 36 days. On day 36, the present study found that the red leaf lettuce plants expressed foliar symptoms that began as chlorotic, reduced plant height, reduced leaf length and diameter, wilt, and dried up before it collapsed at day 45 compared to untreated control lettuce plants. Microscopic observation on lettuce roots showed that the Trichoderma spores invading the root system by mass sporulation and spatial competition possibly impaired plant water uptake and eventually caused plant wilting. Therefore, this study indicates that T. longibrachiatum is among the causal agents of wilt disease in the lettuce plant.

Phytochemical contents and diuretic activity of ethanolic extract of the red leaf lettuce (Lactuca Sativa l.)

This study was conducted to evaluated of phytochemical content and diuretic activity of the red leaf lettuce. Red leaf lettuce were extracted by cold maceration method using 70% ethanol for the 3 days and remaceration for 1 days. The phytocemical content in ethanolic extract were evaluated by qualitatif method. A total of 25 male rats were divided into 5 groups with CMC Na, a standard drug (furosemide 10 mg/kg), and three different doses (200, 300, and 400 mg/kg) of ethanol extract. Parameters used to determine diuresis activity include first urine latency, urine pH and cumulative urine volume. The ethanolic extract induced diuresis in a dose dependent manner as compared to the negative control. Extracts at doses of 200, 300, and 400 mg/kg produced significant diuresis effects (p<0.05) compared to negative controls with values of diuretic action 1.35; 1.43; and 1.53, respectively. In addition, there was a slightly change in the pH of urine samples of the extract-treated group compared with the negative control. Phytochemicals analysis revealed the presence of alkaloids, flavonoids, phenolics, and tannins.

Ultraviolet A and Blue Light Transiently Regulate Total Phenolic and Anthocyanin Concentrations in Indoor-grown Red-leaf Lettuce

In controlled environments, supplementing a light spectrum with ultraviolet A (UVA; 315–399 nm) or blue (B; 400–499 nm) light increases the concentrations of phenolic compounds that can increase quality attributes, such as leaf pigmentation and nutritional quality of lettuce (Lactuca sativa). However, B light and sometimes UVA light can inhibit leaf expansion and biomass accumulation when continuously applied, whereas applying it only at the end of the production cycle can increase lettuce quality with little to no effect on crop yield. Our objective was to quantify the persistency of periodic supplemental UVA or B light and compare end-of-production with continuously applied supplemental light during indoor lettuce production on quality attributes and biomass accumulation. We hypothesized that supplemental UVA or B light would be more effective later, rather than earlier, during production with increasing lettuce quality attributes. We grew ‘Rouxai’ red-leaf lettuce hydroponically at an air temperature of 23 °C under 75 μmol⋅m−2⋅s−1 of red (peak = 664 nm) plus 75 μmol⋅m−2⋅s−1 of warm-white light provided by light-emitting diodes. The supplemental lighting treatments consisted of adding 30 μmol⋅m−2⋅s−1 of UVA (peak= 386 nm) or B (peak = 449 nm) light during the seedling phase (P1; days 4–12), growth phase (P2; days 12–20), finishing phase (P3; days 20–28), or the entire time (ET; days 4–28). Supplemental UVA or B light applied at any individual phase did not inhibit biomass accumulation, whereas enriched B light during the entire production period inhibited fresh mass compared with no supplemental light. Additionally, supplemental UVA or B light during P3 or ET similarly increased total phenolic and anthocyanin concentrations. Finally, applying UVA or B light during P1 or P2 had no residual effect on mature plant growth or quality at harvest. We concluded that the end of the production cycle is the optimal time to apply supplemental UVA or B light to improve lettuce coloration and phenolic content, that earlier application elicits transient responses, and that continuous application improves lettuce quality but inhibits biomass accumulation. Finally, there are potential energy savings by using end-of-production supplemental light compared with continuous application of the same spectrum.

Controlling root zone temperature improves plant growth and pigments in hydroponic lettuce.

Air and root zone temperatures are important environmental factors affecting plant growth and yield. Numerous studies have demonstrated that air temperature strongly affects plant growth and development. Despite the extensive literature on air temperature, comprehensive studies on the effects of root zone temperature (RZT) on plant growth, elemental composition, and pigments are limited. In this study, we carefully observed the effects of RZT in red leaf lettuce to understand its effect on lettuce growth and pigment content. Lettuce (Lactuca sativa, red leaf cultivar 'Red Fire') was grown hydroponically in a plant factory with artificial light under three RZT treatments (15, 25, or 35 °C) for 13 days. We investigated the comprehensive effects of RZT on the production of red leaf lettuce by metabolome and ionome analyses. The 25 °C RZT treatment achieved maximum shoot and root dry weight. The 35 °C RZT decreased plant growth but significantly increased pigment contents (e.g. anthocyanins, carotenoids). In addition, a RZT heating treatment during plant cultivation that changed from 25 to 35 °C RZT for 8 days before harvest significantly increased shoot dry weight compared with the 35 °C RZT and significantly increased pigments compared with the 25 °C RZT. The 15 °C RZT resulted in significantly less pigment content relative to the 35 °C RZT. The 15 °C RZT also resulted in shoot and root dry weights greater than the 35 °C RZT but less than the 25 °C RZT. This study demonstrated that plant growth and pigments can be enhanced by adjusting RZT during different stages of plant growth to attain enhanced pigment contents while minimizing yield loss. This suggests that controlling RZT could be a viable method to improve lettuce quality via enhancement of pigment content quality while maintaining acceptable yields.

Pre-Harvest UVB Irradiation Enhances the Phenolic and Flavonoid Content, and Antioxidant Activity of Green- and Red-Leaf Lettuce Cultivars

As a promising environmental protection technology, the application of ultraviolet B irradiation in vegetable production has been widely considered. However, the effect of UVB irradiation varies with different plant varieties. In this study, we investigated the effects of two UVB intensities (0.7, 1.4 W m−2) on the accumulation of phenolics and flavonoids, and antioxidant activity of green-leaf and red-leaf lettuce (Lactuca sativa L.) 7 days prior to harvest. The results indicated that short-term (within 2 days) UVB treatment could promote the increase in total chlorophyll content of red-leaf lettuce and green-leaf lettuce, which increased by 49.8% and 20.6% compared with day zero, respectively, and was beneficial to the synthesis of carotenoids of red-leaf lettuce. Extending UVB exposure time significantly decreased chlorophyll a/b value of green-leaf lettuce from 0.92 to 0.63, and simultaneously increased the accumulation of antioxidant substances such as flavonoids, which were increased by 90.0% and 183.4% compared with day zero for UVB-0.7 and UVB-1.4 treatments of red-leaf lettuce, 84.1% and 110.9% of green-leaf lettuce. In contrast, red-leaf lettuce had a higher accumulation level of secondary metabolites, faster scavenging rate of free radicals, and stronger ability to resist UVB stress. Our results suggest that supplementation of low-dose UVB radiance prior to harvest can improve the secondary metabolite content and antioxidant activity of the two kinds of lettuce. This research provided a theoretical basis for improving lettuce quality by pre-harvest UVB treatment in controlled environmental agriculture.

PHYTOCHEMICAL ANALYSIS, ANTIOXIDANT ACTIVITY AND FTIR SPECTROSCOPIC ANALYSIS OF RED LEAF LETTUCE AND GREEN LEAF LETTUCE (LACTUCA SATIVA L.)

This study was conducted to analyze the phytochemical compounds, the profile of infrared spectrophotometric, total phenolic contents (TPC) and antioxidant activity of ethanol extract of red leaf lettuce (RL) and green leaf lettuce (GL). RL and GL were extracted with 70 % ethanol using the maceration method for 3 days and re-maceration for 1 day. The secondary metabolites in ethanol extracts were evaluated by phytochemical analysis and profile spectra infrared. Estimation of TPC was conducted by the FolinCiocalteu methods. The antioxidant activity assay was conducted by ABTS and DPPH methods. The determination of TPC showed that the ethanol extract of RL was higher than the ethanol extract of GL. RL has stronger antioxidant activity than GL. The presence of hydroxyl group in the phenolics directly correlates with the antioxidant activity, so consumers could use them as natural antioxidants or to functionalize foods. This understanding is important for improving the safety and quality of leaf lettuce.

UV-A for Tailoring the Nutritional Value and Sensory Properties of Leafy Vegetables

This study aims to expand the artificial lighting potential of controlled environment cultivations systems by introducing UV-A (~315–400 nm) wavelengths into the traditional, visible spectrum lighting, seeking to improve the nutritional and sensory value of cultivated leafy vegetables. The experiment was conducted in a closed climate-controlled chamber, maintaining 21/17 °C day/night temperature, ~55% relative humidity, and a 16 h photo/thermo period. Several genotypes of leafy vegetables, red and green leaf lettuce cultivars, mustard, and kale were cultivated under 250 µmol m−2s−1 basal LED lighting, supplemented by 385 nm UV-A or 405 UV-A/violet wavelengths for 1.1 mW cm−2 for 12 h photoperiod for the whole cultivation cycle. The results show that UV-A/violet light impacts on leafy vegetable growth, free radical scavenging activity, sugar, and phytochemical (α tocopherol, α + β carotenes, epicatechin, rosmarinic and chicoric acid contents) are species-specific, and do not correlate with untrained consumer’s sensory evaluation scores. The 405 nm light is preferable for higher antioxidant and/or sensory properties of kale, mustard, and green leaf lettuces, but both UV-A wavelengths reduce growth parameters in red leaf lettuce.

Experimental non-invasive methodology to assess light-induced pigment changes in green and red leaf lettuce

Experimental non-invasive methodology to assess light-induced pigment changes in green and red leaf lettuce

End-of-production Ultraviolet A and Blue Light Similarly Increase Lettuce Coloration and Phytochemical Concentrations

Anthocyanins are a group of human-health-promoting phenolic compounds that influence the pigmentation of red-leaf lettuce (Lactuca sativa). Ultraviolet A (UVA; 315–399 nm) and blue (B; 400–499 nm) light can increase the concentrations of phenolic compounds but also suppress cellular expansion, which can limit harvestable biomass accumulation. It is not known whether UVA or B light is more effective at increasing phenolic compound concentrations when they are each applied at the same photon flux density. Our objective was to evaluate the efficacy of UVA and B light when added during the end of production (EOP) at promoting phenolic compound synthesis and red-leaf coloration without limiting biomass accumulation. We grew red-leaf lettuce ‘Rouxai’ in a controlled indoor environment at an air temperature of 22 °C under warm-white and red light-emitting diodes (LEDs). On day 24, 30 or 60 µmol·m−2·s−1 from UVA, B, UVA plus B, or red plus green LEDs was added during the last 6 days of the 30-day production period. UVA and B light, alone or combined, similarly increased leaf redness (by up to 72%), total phenolic concentration (by up to 92%), total anthocyanin concentration (by up to 2.7-fold), and relative chlorophyll concentration (by up to 20%) and did not inhibit growth, compared with lettuce grown without EOP supplemental lighting. Considering B light was as effective as UVA light at increasing leaf color and phytonutrient density and that B LEDs are more electrically effective, economical, and durable, an enriched blue-light spectrum at the EOP is a comparatively sustainable method to increase crop quality without suppressing biomass accumulation.

Microbispofurans A-C, plant growth-promoting furancarboxylic acids from plant root-derived Microbispora sp.

Microbispofurans A-C (1-3), new alkyl/alkenyl furancarboxylic acids, were isolated from the culture extract of the plant root-derived Microbispora sp. RD004716. The planar structures of 1-3 were determined by extensive analysis of 1D and 2D NMR spectroscopic data. Although 1-3 showed no appreciable antimicrobial activity or cytotoxicity, strong plant growth-promotion activity of the germinated red leaf lettuce seeds was observed at 10 μM. Furancarboxylic acids and their methyl esters were found in actinomycetes and fungi; however, the isolation of furandicarboxylic acid was unprecedented.

Green Leaf, Red Leaf, and Romaine Lettuce Breeding Lines with Resistance to Leafminer, Corky Root, and Downy Mildew

Green Leaf, Red Leaf, and Romaine Lettuce Breeding Lines with Resistance to Leafminer, Corky Root, and Downy Mildew

Quercetin and Its Nano-Formulations for Brain Tumor Therapy-Current Developments and Future Perspectives for Paediatric Studies.

The development of efficient treatments for tumors affecting the central nervous system (CNS) remains an open challenge. Particularly, gliomas are the most malignant and lethal form of brain tumors in adults, causing death in patients just over 6 months after diagnosis without treatment. The current treatment protocol consists of surgery, followed using synthetic drugs and radiation. However, the efficacy of these protocols is associated with side effects, poor prognosis and with a median survival of fewer than two years. Recently, many studies were focused on applying plant-derived products to manage various diseases, including brain cancers. Quercetin is a bioactive compound derived from various fruits and vegetables (asparagus, apples, berries, cherries, onions and red leaf lettuce). Numerous in vivo and in vitro studies highlighted that quercetin through multitargeted molecular mechanisms (apoptosis, necrosis, anti-proliferative activity and suppression of tumor invasion and migration) effectively reduces the progression of tumor cells. This review aims to summarize current developments and recent advances of quercetin's anticancer potential in brain tumors. Since all reported studies demonstrating the anti-cancer potential of quercetin were conducted using adult models, it is suggested to expand further research in the field of paediatrics. This could offer new perspectives on brain cancer treatment for paediatric patients.