Nitrate In Lettuce Research Articles

Improved estimates of expanded measurement uncertainty.

Measurement uncertainty (MU) is often estimated (sometimes initially as repeatability) using a limited number of single measurement values (n ≪ 30), or of duplicate measurements on duplicated samples, in order to include the contribution from sampling. In cases such as this where the uncertainty estimate is based on limited data, the common use of a coverage factor of 2.0, based on an assumed normal distribution, to give an approximate 95% confidence interval can result in an underestimate of the expanded MU. Where n is much lower than 30 (e.g., n = 8), this can lead to a serious underestimate. More accurate estimation of the coverage factor, for both the classical and robust ANOVA (e.g., in new software RANOVA v4.0) gives more reliable estimates of the expanded MU by calculating coverage factors based on the t-distribution. A case study for nitrate in lettuce shows that the more accurate coverage factor (of ∼2.3) substantially increases the expanded MU estimates by 13-14%.

Nitrate Surveillance Monitoring Program Annual Report (April 2022 to March 2023)

This is the 2022-23 data for the project FS101228 - Nitrate Surveillance Monitoring Program. Previous reports are available: <a href=“https://doi.org/10.46756/sci.fsa.uau489” style=“display: inline-block; padding: 10px 20px; background-color: #007d75; color: white; text-align: center; text-decoration: none; border-radius: 5px;”>Nitrate Surveillance Monitoring Program (Annual Report May 2021 - March 2022)</a> <a href=“https://www.food.gov.uk/research/chemical-hazards-in-food-and-feed/nitrate-monitoring-in-spinach-and-lettuce-surveillance-programme” style=“display: inline-block; padding: 10px 20px; background-color: #007d75; color: white; text-align: center; text-decoration: none; border-radius: 5px;”>Nitrate monitoring in spinach and lettuce - surveillance programme</a> #Summary While the UK is no longer part of the EU, monitoring activities have continued under GB retained law 1258/2011 since January 2021. The requirement to carry out monitoring for nitrate in lettuce, spinach and rocket is being met by the UK Nitrate Surveillance Programme. Results are presented for the period between 1 April 2022 and 31 March 2023. The survey monitors compliance in UK and gathers data on occurrence levels in leafy green vegetables. This report covers the survey period 2022 to 2023. The current round of surveys commenced in 2020. This surveillance has been undertaken since May 1996, except for 2019-20, and reported in earlier MAFF (now Defra)/FSA Food Surveillance Information Sheets. Monitoring of UK grown lettuce, spinach and rocket is currently led by RSK ADAS Ltd (ADAS) in partnership with NRM Laboratories. The survey monitors compliance in UK and gathers data on occurrence levels in leafy green vegetables. The survey period covers the years 2022 to 2023. The survey commenced in 2020. A total of 200 samples were collected within the sampling period, comprising of 120 lettuce, 18 rocket, 21 spinach samples. A further 41 samples categorised at ‘Other Green Leafy Vegetables’ was comprised of samples including chard, Chinese leaves, mizuna, kale, and pak choi. The lowest average nitrate concentration was recorded in summer-grown iceberg lettuce (1045.1 mg/kg). One iceberg sample exceeded the maximum nitrate concentration. The highest average nitrate concentrations were seen in ‘other leafy green vegetables’ (7701.3 mg/kg) and in summer-grown rocket (7235.7mg/kg). The number of samples exceeding the maximum levels decreased this year to 6 samples – one sample of Iceberg, two samples of open-air non-iceberg lettuce sampled in the summer, two samples of rocket sampled in the summer and two samples of spinach. A further 14 samples were within 10% of the maximum level. Historical trends indicate that the average annual nitrate concentrations were again elevated for rocket and spinach, and the proportion of samples that exceeded the maximum level increased. Consistent with previous years of this project, a strong correlation was found between nitrate concentration and sampling date, with samples collected later in the season showing greater concentrations, indicating potential interactions between nitrate accumulation and climate, particularly light levels, available soil moisture and any accumulation of nitrate in the soil. 2022-23 was warmer (particularly during the summer), with less rainfall and more hours of sunshine than in previous years.

Effects of the supernatant of Chlorella vulgaris cultivated under different culture modes on lettuce (Lactuca sativa L.) growth.

CO2 capture by microalgae is a feasible strategy to reduce CO2 emissions. However, large amounts of cell-free supernatant will be produced after microalgal harvesting, which may be harmful to the environment if it is disorderly discharged. In this study, Chlorella vulgaris (C. vulgaris) was cultivated under three common cultivation modes (autotrophic culture (AC), heterotrophic culture (HC) and mixotrophic culture (MC)), and the obtained supernatant was used as fertilizer to investigate its effect on the growth of lettuce. The biomass concentration of C. vulgaris cultivated under MC and HC was 3.25 and 2.59 times that of under AC, respectively. The contents of macronutrients in supernatant obtained from AC were higher than those of MC and HC. However, the contents of amino acids and hormones in supernatant obtained from MC and HC were higher than those of AC. The fresh shoot weight, fresh root weight and root length of lettuce treated with supernatant were significantly higher than that of control treatment. In addition, the contents of chlorophyll, soluble sugar and soluble protein in lettuce treated with supernatant were also higher than that of control treatment. However, the contents of nitrate in lettuce treated with supernatant was lower than that of control treatment. These results showed that the supernatant could promote the growth of lettuce and was a potential of fertilizer for crop planting.

Yield and quality of lettuce (Lactuca sativa L.) depending on variety and type of nitrogen fertilizer

The aim of this research was to determine the effect of the application of different types of nitrogen fertilizer in five different varieties of lettuce on yield. The experiment was performed in the open field, in the spring cycle of growing during 2018 and 2019. The size of the base plot was 3 m2, and the trial was set up in a random block system. The trial covered the application of various forms of nitrogen fertilizers: ammonium sulphate, ammonium nitrate and urea. The applied nitrogen dose is 100 kg/ha (May 10th 2018 and May 8th 2019). Samples for the analysis of vitamin C and nitrate content, as well as yield determination, were carried out at the stage of the technological maturity of lettuce (60-62 days after seedling). The average weight of lettuce, depending on the variety, varied in the range of 211.3 g to 258.7 g. The use of ammonium nitrate resulted in the highest average weight of lettuce head (246.7 g), followed by the use of urea (238.9 g) and the lowest by the use of ammonium sulphate (221.0 g). The nutritional value of lettuce (vitamin C content) shows that depending on the applied form of nitrogen in the fertilizer, the highest content of vitamin C was determined by urea (10.86 mg/100 g), then ammonium sulphate (9.61 mg/100 g), and the lowest by ammonium nitrate (7.38mg/100g). The lower content of vitamin C was found in varieties of lettuce with red leaves compared to varieties with green leaves. The accumulation of nitrate in lettuce leaves directly depends on the variety and the applied fertilizer. The highest nitrate content was with ammonium nitrate (2355.6 mg/kg). The accumulation of nitrate in lettuce varieties with red leaves was higher compared to varieties with green leaves. Keywords: Lettuce, Nitrate, Vitamin C, Yield, Open field

Effect of Irrigation Water and Organic Fertilizer on Reducing Nitrate Accumulation and Boosting Lettuce Productivity

Accumulation of high level of nitrate (NO3−) in leaves is a serious issue for vegetable crops like lettuce (Lactuca sativa L.). Therefore, this study aimed to limit NO3− level by adjusting the balance between fertilization and irrigation program in lettuce. In a strip plot design with three replicates, lettuce plants were grown under four fertilizer treatments and three irrigation regimes. Three organic fertilizers (biochar, compost and vermicompost), in addition to mineral fertilizer, were used. The irrigation regimes were 60, 80 and 100% of crop evapotranspiration, ETc (ETc60, ETc80, and ETc100). Nitrogen (N), phosphorus (P) potassium (K) and organic matter (OM) in soil as well as yield, N, P, K and NO3− of lettuce were estimated. Findings showed that vermicompost or biochar (with any irrigation regime) as well as compost with irrigation by ETc60 were the effective combinations for increasing K content in soil after harvest. Under irrigation by ETc80 or ETc100, vermicompost or biochar were the efficient treatments for increasing lettuce yield equaling the farmer common practice (ETc100 x mineral fertilizer). Under irrigation by ETc60, mineral fertilizer or vermicompost showed the highest lettuce leaf content of K. Moreover, ETc60 or ETc80 x mineral fertilizer recorded the maximum NO3− content of lettuce leaves. The accumulation of nitrate in lettuce leaves owing to mineral fertilizer reached about 1.24 times than that of organic fertilizers. Compost x ETc80 or ETc100 showed the minimal NO3–N accumulation, hence, high relative reductions in NO3–N accumulation as compared to the common practice (ETc100 x mineral fertilizer) were observed. In conclusion, irrigation by 80% instead of 100% of crop evapotranspiration of organically fertilized lettuce (especially with vermicompost) could be adopted since such practice recorded high lettuce productivity with low NO3− content.

Cadmium Accumulation in a Tropicalized Lettuce Variety Under Overfertilization Simulation

AbstractCadmium (Cd) can accumulate in vegetables and enter the food chain. The production of vegetables usually uses excessive amounts of fertilizers which bring environmental and health damages. The authors investigate the relationship between fertilization with nitrogen (N), phosphorus (P), and potassium (K) and the accumulation of Cd and nitrate in lettuce of the tropicalized variety “Gloriosa.” The experiment is under greenhouse conditions in a 2×2 factorial design, with the addition or not of 10 mg kg−1 Cd to the soil, and the use of one and three times the recommended rate of N, P, and K for lettuce crop. The higher fertilization rate is related to the increase of Cd in the shoots. Gloriosa lettuce shows high Cd‐accumulation capacity, especially in the shoots, evidencing great Cd‐translocation. Fresh leaves reach up to 8 mg kg−1 Cd, higher than permissible limits, but high Cd‐tolerance and no visual symptoms of toxicity or reduction in biomass production. In plants grown with three times the recommended rates of N, nitrate concentrations are within the permissible limits for leafy vegetables. To avoid Cd‐accumulation, besides monitoring soil Cd, it would be necessary to establish safe rates of fertilization for the cultivation of tropicalized lettuce varieties.

Root-applied glycinebetaine decreases nitrate accumulation and improves quality in hydroponically grown lettuce

Leafy vegetables like lettuce (Lactuca sativa L.) naturally have high nitrate content and the European Commission has set maximum level for nitrate in lettuce. Glycinebetaine is an organic osmolyte alleviating plant stress, but its role in leaf nitrate accumulation remains unknown. The uptake of glycinebetaine by lettuce roots, and its potential to regulate lettuce nitrate content and improve plant quality were investigated. Two hydroponic lettuce experiments were conducted with different glycinebetaine application rates (Exp1: 0, 1, 7.5, and 15 mM; Exp2: 0, 1 + 1 + 1, 1 + 10, and 4 mM). Plants were analyzed at varying time points. Root application resulted in glycinebetaine uptake and translocation to the leaves. Glycinebetaine concentrations > 7.5 mM reduced leaf nitrate up to 40% and increased leaf dry matter content. Glycinebetaine showed a positive effect on leaf mineral and amino acid composition. Thus, glycinebetaine could be a novel strategy to reduce the nitrate content in hydroponic lettuce.

Regulated Salinity Eustress in a Floating Hydroponic Module of Sequentially Harvested Lettuce Modulates Phytochemical Constitution, Plant Resilience, and Post-Harvest Nutraceutical Quality

A mild salinity stress (eustress) may modulate the induction of the plant defense system in horticultural crops and the synthesis of phytochemical components able to enhance plant resilience, post-harvest performance, and the nutraceutical quality of produce. However, the choice of the correct eustress type and dose to induce the synthesis of these protective phytochemicals is pivotal to avoid potential interference with plant growth and productivity. In order to study how green and red lettuce (Lactuca sativa L.) plants equilibrate the nutritional and nutraceutical components of quality with yield components, we applied iso-osmotic concentrations of three different salts (20 mM NaCl, 20 mM KCl, and 13.3 mM CaCl2, with a final total ionic concentration of 40 mM) in combination with two successive harvests in a floating raft system. The biometric parameters, mineral composition, bioactive compounds, and antioxidant activity of both cultivars were analyzed. The green cultivar had a superior response concerning biometric traits and productivity compared to the red one during the first cut but lower phytochemical content (e.g., ascorbic acid). The effect of cut order, independently of cultivar and salinity treatments, demonstrated that at the first harvest plants could redirect metabolism by increasing the lipophilic antioxidant content (LAA) at the expense of plant yield, therefore increasing plant resilience and post-harvest nutraceutical quality; whereas, at the second harvest, plants reverted principally to tissue expansion. The treatments with iso-osmotic salt concentrations did not affect K and Mg ion contents but further increased LAA and resulted only in a moderate decrease of fresh yield. The lettuce nitrate content was reduced during the second cut only when lettuce plants were treated with NaCl and especially CaCl2.

Red and blue wavelengths affect the morphology, energy use efficiency and nutritional content of lettuce (Lactuca sativa L.)

Since red (R) and blue (B) LED light has different quantum efficiency and photoelectric conversion efficiency, mixed RB with different proportions of R and B results in varied energy consumption. In order to improve the energy use efficiency of the closed-type plant production systems, the effects of R and B proportions on the electric use efficiency (EUE), light use efficiency (LUE) as well as the quality of butter leaf lettuce were evaluated in this study. Lettuce seedlings were cultivated in a plant factory with artificial lighting (PFAL) and subjected to eleven combinations of R and B (100%R, 90%R, 80%R, 70%R, 60%R, 50%R, 40%R, 30%R, 20%R, 10%R, 0%R; the rest of the photons in each treatment were B) with the same total photosynthetic photon flux density (PPFD) and photoperiod (200 ± 3 μmol·m−2·s−1, 16 h) for 35 days. The results showed that palpable petiole distortion appeared when R proportion was more than 70% and the distortion was aggravated with the increase of R proportion. The highest EUE and LUE were both detected in lettuce under 90%R treatment, which were respectively 3.64% and 1.20%. The least number of photons and the least electricity amount required to produce 1 g dry weight of lettuce was respectively 2.92 mol and 1.67 MJ, which were both detected in lettuce treated with 90%R. The sucrose content in lettuce treated with more than 50%R was significantly higher than those treated with less than 50%R (50%R included). Lettuce treated with 80%R possessed the highest soluble sugar content as well as the lowest crude fiber and nitrate content (not significantly different with the minimum values). R proportion exceeding 50% in mixed RB light was beneficial to the accumulation of hexose and sucrose, as well as the decomposition of nitrate in lettuce. The vitamin C content in lettuce treated with 100%R was significantly higher than that in lettuce under other treatments in the study. On the whole, the study indicated that the proportions of R and B affected the energy use efficiency and quality of lettuce in closed plant factory, however the responses of plants to the proportions of R and B varied according to different indexes. Thus, some indexes of top priority should be determined before choosing the optimal proportions of R and B.

Effect of Bio-Priming with Plant Growth Promoting Bacteria on Growth and Biochemical Characteristics, Phenol, Flavonoid, Vitamin C and Nitrate in Lettuce (Lactuca sativa L.) Rabicon Cultivar in Different Growth Substrates

Effect of Bio-Priming with Plant Growth Promoting Bacteria on Growth and Biochemical Characteristics, Phenol, Flavonoid, Vitamin C and Nitrate in Lettuce (Lactuca sativa L.) Rabicon Cultivar in Different Growth Substrates

PENGARUH PENAMBAHAN KALIUM NITRAT DALAM LARUTAN HARA PADA MEDIA KASCING TERHADAP PERTUMBUHAN SELADA (Lactuca sativa L.)

This research was conducted with the aim to find out the effect of the addition of potassium nitrate in lettuce as a medium and critical level of concentration(electrical conductivity)of nutrient solution. Research is organized in the form of a pot experiment. The experimental design used was Complete RandomizedBlock Design (CRBD)) with three replications. The treatment consists of 12 levels of concentrations or nutrient solution electrical conductivity with the addition of potassium nitrate to lettuce plant. The treatment level of concentrations (conductivity) of nutrient is as follows; L0 = 0.00; L1 = 1.25; L2 = 2.50; L3 = 3.75; L4 = 5.00; L5 = 6.25; L6 = 7.50; L7 = 8.75; L8 = 10.00; L9 = 11.25; L10 = 12.50 and L1 = 13, 75 g 100 L-1 water. Value concentrations of electrical conductivity each nutrient solution concentrations are: L0 = 0.06; L1 = 0.26; L2 = 0.46; L3 = 0.66; L4 = 0.86; L5 = 1.06; L6 = 1.26; L7 = 1,46; L8 = 1.66; L9 = 1,86; L10 = 2.06 and L1 = 2.26. dS m-1. The result of the experiment showed that addition of KNO3 highly significant effect on the increase in fresh weight and dry weight of shoot per plant. Fresh weight and oven-dry weight of shoot per plant was significantly increased in a quadratic with increasing concentrations of KNO3are optimum for growth of plant shoot weight were at 12.23 g in 100/of water on electrical conductivity equivalent to 2.01 dS.m-1. The addition of concentration of KNO3to nutrient solution does not affect on N and other nutrient solution on shoot tissue of lettuce plant but the concentrations of P and K in plant shoot tissue were significantly increased linearly with the provision of KNO3.

Mineral nitrogen fertilization effects on lettuce crop yield and nitrogen leaching

The low efficiency of N fertilization in soils used to grow vegetables and the consequent need to add high levels of the nutrient are the major cause of nitrate contamination of groundwater and freshwater, which calls for practices to increase N fertilization efficiency in these crops. Two experiments were carried out in Jaboticabal, Brazil, to evaluate the effects of topdressing N fertilization on crisphead lettuce (Lactuca sativa) yield, nitrate accumulation in plant shoots, and soil nitrogen leaching in two growing seasons, summer and winter. Both experiments were designed as randomized blocks with seven treatments and five replications (35 plots). The treatments were seven different rates of topdressing N. The rates of N application were 0, 30, 60, 90, 120, 150, and 180 kg N ha -1 in the form of urea, applied 8 (20%), 16 (40%), and 24 (40%) days after transplanting. Lettuce was harvested 34 and 42 d after transplanting in the summer and winter, respectively. Plant nitrate concentrations were determined in dry matter. After the harvest, soil samples were collected at the 0-20, 20-40, and 40-60 cm layers to quantify nitrogen in the forms of ammonium and nitrate. The data were submitted to analysis of variance and nonlinear regression analysis. Better use of topdressing nitrogen fertilization for lettuce growth was observed at rates lower than 60 kg N ha -1. Rates of N up to 180 kg N ha -1 did not elevate lettuce nitrate concentrations over the levels allowed for consumption but increased the amount of nitrogen lost through leaching. Decreasing N rates resulted in a similar yield and lower nitrogen leaching, improving both the environmental and economic aspects.

Nutrient Dynamics of Different Plants in an Aquaponics Aquaculture System

<div><!--block-->This study evaluates the performance of plants grown at different times in the aquaponics system-a modern and sustainable production method—on water quality. In the established aquaponics system, this study monitored the growth performance of koi fish, Cyprinus carpio var. koi, and different plants (lettuce, Lactuca sativa, var. Crispa as a leafy plant and strawberry, Fragaria sp. as a fruit plant), pertaining to macro nutrient cycling and effects of plants on water quality parameters. Experiments in an aquaponics system comprising a biological filter and plant unit found that the removal rates of macro nutrients from the system were as follows: 1) 4295% for phosphate and 55.45% for nitrate in lettuce and 2) 35.49% for phosphate and 46.36% for nitrate in strawberries. It was observed that, in general, the rate of removing macro nutrients was higher in the lettuce experiment than in the strawberries one. The elimination rates of macro nutrients in this study show that increasing dissolved nutrients in an aquarium is effectively reduced, which confirms that this production system is an environmentally-friendly and sustainable method.</div>

Potential health impacts from different vegetable nitrate intake scenarios and providing strategies to manage the risks for Iranian population.

Health risk from nitrate was predicted for different scenarios of vegetable consumption and nitrate contents in Iran. Finally, certain management scenarios were presented for nitrate risk mitigation under worst-case scenario considering each vegetable contribution in nitrate intake. Two fruit (bell pepper and tomato) and two leafy vegetables (lettuce and mint) were sampled in a combined randomized method from fields, greenhouses, and markets of Isfahan province, Iran during October to December 2015. To assess the potential health impacts of nitrate from the vegetable ingestion, the present status and three different scenarios of increasing vegetable consumption and/or increasing plant nitrate concentrations were considered. Two management scenarios for reducing the total nitrate intake below the allowable values were predicted. By increasing vegetable consumption under scenario 1 and nitrate concentration under scenario 3, the total hazard quotient (THQs) was increased, although the highest increase (12-fold) in the THQs was provided by lettuce. Health risk from nitrate for sensitive groups was effectively reduced by a 70% decrease in lettuce nitrate concentration. In the second management scenario, decreasing upper nitrate concentrations in the other sources (except lettuce) by 30% declined nitrate intake in children (< 6years old) and boys (7-14years old) below acceptable daily intake (ADI). By taking into account the increases in the amounts of consumption and nitrate in vegetables at different scenarios, it was revealed that the critical factor for a high dietary exposure to nitrate is not the absolute amount of vegetables consumed but the type of vegetable (lettuce) and the concentration of nitrate related to the conditions of production. Therefore, to manage any risks to human health from dietary nitrate exposure resulting from vegetable consumption, focus on lettuce instead of taking other vegetables equally into account is needed.

Yield, nitrogen recovery efficiency and quality of vegetables grown with organic waste-derived fertilisers

More sustainable production of high-quality, nutritious food is of worldwide interest. Increasing nutrient recycling into food systems is a step in this direction. The objective of the present study was to determine nitrogen (N) fertiliser effects of four waste-derived and organic materials in a cropping sequence of broccoli, potato and lettuce grown at two latitudes (58° and 67°N) in Norway during 3 years. Effects of anaerobically digested food waste (AD), shrimp shell (SS), algae meal (AM) and sheep manure (SM) at different N application rates (80 and 170 kg N ha−1 for broccoli, and 80 and 60 kg N ha−1 for potato and lettuce, respectively) and residual effects were tested on crop yield, N uptake, N recovery efficiency (NRE), N balance, N content in produce, mineral N in soil, product quality parameters and content of nitrate in lettuce. Mineral fertiliser (MF) served as control. Effects on yield, N uptake, NRE, N balance and product quality parameters could to a great extent be explained by estimated potentially plant-available N, which ranked in the order of AD > SS > SM > AM. Results for crops fertilised with AD and SS were not significantly different from MF at the same N application rate, while AM, in agreement with its negative effect on N mineralisation, gave negative or near-neutral effects compared to the control. No residual effect was detected after the year of application. The results showed that knowledge about N dynamics of relevant organic waste-derived fertilisers is necessary to decide on the timing and rate of application.

Interaction effects of light intensity and nitrogen concentration on growth, photosynthetic characteristics and quality of lettuce (Lactuca sativa L. Var. youmaicai)

Light intensity and nitrogen concentration of nutrient solution are considered crucial for the contents of vitamin C and nitrate in cultivated leaf vegetables. We here investigated the effects of various combinations of light intensity (60, 140 and 220μmolm−2s−1) and nitrogen concentration (7, 15 and 23mmolL−1) of the solution on the growth, photosynthetic characteristics, vitamin C and nitrate content of lettuce. Our results demonstrate that the lettuce had the largest dry biomass at the high illumination of 220μmolm−2s−1 and low nitrogen of 7mmolL−1. The higher light and low nitrogen also contributed to the accumulation of vitamin C and decrease of nitrate in lettuce leaves. The effect of nitrogen supply on chlorophyll concentrations was more efficient under low light than high illumination. Our results reveal that there was an obvious interaction between light intensity and nitrogen available for the photosynthesis, yield and quality of lettuce. This study provides valuable insights into the combinational regulation of light intensity and nitrogen supply for improving growth and nutritional quality of vegetables grown in greenhouse and plant factory.

Nitrate Content and Expression of Putative Nitrate Transporter Genes in Lettuce Fertilized with Nitrogen Fertilizers

ABSTRACTNitrate accumulation in plants is influenced by environmental conditions and genetic variability. It is important to develop approaches that could be used to reduce nitrate levels in lettuce (Lactuca sativa L.) because nitrate accumulated in leaves can cause harmful health effects in humans. A greenhouse experiment was conducted to determine effects of ammonium nitrate or urea nitrogen on lettuce fresh weight, nitrate content, and characterization of nitrate transporter genes in lettuce. Head fresh weight in cultivars grown with the nitrogen fertilizers differed. All cultivars accumulated more nitrates with urea than with ammonium nitrate fertilizer. ‘Great Lakes’ had lower nitrate accumulation than other cultivars due to urea or ammonium nitrate treatment. Lettuce nitrate transporter genes LsNRT1 and LsNRT2 were detected and their expression level varied due to cultivar and leaf position. ‘Great Lakes’ had low mRNA levels of LsNRT1 and LsNRT2 in leaves compared to other cultivars. ‘Great Lakes’ could be used for lettuce production due to high yield and lower nitrate content.

Accumulation and Primary Metabolism of Nitrate in Lettuce (Lactuca Sativa L. Var. Youmaicai) Grown Under Three Different Light Sources

ABSTRACTLight-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.

Effects of different light intensities on anti-oxidative enzyme activity, quality and biomass in lettuce

Recently, the worldwide demand for romaine lettuce (Lactuca sativa L.) has been increasing. Thus, regulation measures of supplementary or shading light are often used in the production of lettuce in some regions. However, inconsistent results on the light saturation point of lettuce from previous studies do not facilitate the regulation of light intensity. In the present study, the effects of different light intensities on anti-oxidative enzyme activity, yield and quality of lettuce were investigated. The results reveal the following: (1) judged by the dynamics of anti-oxidative enzyme activity, there was no light stress to occurr in the 100, 200 and 400 &amp;mu;mol/m&lt;sup&gt;2&lt;/sup&gt;s treatments, a mild light stress occurred in the 600 &amp;mu;mol/m&lt;sup&gt;2&lt;/sup&gt;s treatment, and a serious light stress occurred in the 800 &amp;mu;mol/m&lt;sup&gt;2&lt;/sup&gt;s treatment; (2) increased light intensity gradually reduced the contents of soluble protein and nitrate in lettuce, whereas the content of soluble sugar remarkably increased. The biomass of a single plant of lettuce in the 600 &amp;micro;mol/m&lt;sup&gt;2&lt;/sup&gt;streatment was the highest and second highest in the 400 &amp;micro;mol/m&lt;sup&gt;2&lt;/sup&gt;streatment but was the lowest in the 100 &amp;micro;mol/m&lt;sup&gt;2&lt;/sup&gt;s treatment. No significant difference in the biomass of single plant was observed between the 400 and 600 &amp;micro;mol/m&lt;sup&gt;2&lt;/sup&gt;s treatments. Based on these results, the range of 400 &amp;micro;mol/m&lt;sup&gt;2&lt;/sup&gt;s to 600 &amp;micro;mol/m&lt;sup&gt;2&lt;/sup&gt;s is a recommendablelight intensity for lettuce production.

CONTENIDO DE NITRATOS Y PROTEÍNA EN LECHUGA CRESPA Y AMARANTO HORTÍCOLA PRODUCIDOS CON ENMIENDA Y UREA

In Argentina, lettuce (Lactuca sativa L.) is the most common vegetable used in salads, while amaranth (Amaranthus mantegazzianus Pass.) is characterized by its high production of green matter, with high protein and mineral levels; both species are considered accumulators of nitrate, so in order to avoid health problems for the consumer, the European Commission regulates the levels of nitrate in lettuce. In order to assess the accumulation of nitrates in both species and evaluate the protein levels and dry matter content, a trial was conducted at the Faculty of Agronomy, UNLPam, Santa Rosa, La Pampa, Argentina. On December 28, 2009, crisp lettuce was transplanted and amaranth was sown. Four levels of fertilization were added for both species: 1) Compost base: 10 dm 3 ·m -2 moderately composted manure, 2) Double Compost: 20 dm3·m-2 moderately composted manure, 3) Compost base + 30 kg·ha-1 urea and 4) Compost base + 60 kg·ha-1 urea. An experimental design of randomized complete blocks with five replications was employed; significant differences in nitrate levels between species and levels of fertilization were obtained. The values in lettuce were 2.9 % dry basis and 2,634 mg·kg-1 fresh-1 and in ama