•Continuous light (CL) increased edible nutrition quality and concomitantly decreased nitrate content.•Green light supplementation promoted nitrate reductase (NR) and nitrite reductase (NiR) related ...gene expression.•Inclusion green light induced the activities of nitrogen assimilation enzymes under short-term CL.
Most leafy vegetables can accumulate large amounts of nitrate, which are often associated with harmful effects on human health. Nitrate assimilation in plants is determined by various growth conditions, especially light conditions including light intensity, light duration and light spectral composition. Red and blue light are the most important since both drive photosynthesis. Increasingly, recent evidence demonstrates a role for green light in the regulation of plant growth and development by regulating the expression of some specific genes. However, the effect of green light on nitrate assimilation has been underestimated. In this study, lettuce (Lactuca sativa L. cv. Butterhead) was treated with continuous light (CL) for 48 h by combined red and blue light-emitting diodes (LEDs) supplemented with or without green LED in an environment-controlled growth chamber. The results showed that nitrate reductase (NR) and nitrite reductase (NiR) related-gene expression and nitrate assimilation enzyme activities were affected by light spectral composition and light duration of CL. Adding green light to red and blue light promoted NR and NiR expressions at 24 h, subsequently, it reduced expression of these genes during CL. Compared with red and blue LEDs, green light supplementation significantly increased NR, NiR, glutamate synthase (GOGAT) and glutamine synthetase (GS) activities. Green-light supplementation under red and blue light was more efficient in promoting nutritional values by maintaining high net photosynthetic rates (Pn) and maximal photochemical efficiency (Fv/Fm).
Plants on the land quickly wilt and perish due to the extended dry season, severe temperatures, heat, and glaring sunlight. This issue has impacted red lettuce, which has commercial value and high ...marketing prospects. Providing plants with water and fertilizer during the dry season must be efficient and exact. Excess fertilizer application pollutes the environment. In the dry season, drip irrigation with IoT-based liquid fertilizer distribution is projected to save water and fertilizer due to low discharge and high frequency. The study's goal is to provide effective autonomous distribution of water and fertilizer to red lettuce plants in order to achieve precision environmentally friendly agriculture. A split-plot design with a main plot and subplots was used to structure the research. Each treatment in one replication contained 5 plant samples, for a total of 60 plants in this study, with weekly watering and fertilization. The findings show that an IoT-based automatic water supply and drip fertilization system can precisely regulate the distribution of water and fertilizer to red lettuce plants, thereby improving water efficiency, farmer energy efficiency, and environmental friendliness.
•Adding FR light stimulates biomass production of indoor cultivated lettuce.•Additional FR light reduces the leaf photosynthetic capacity without affecting plant growth.•Adding FR light at the ...end-of-day has highest plant radiation use efficiency.
Understanding the wavelength-dependence of plant responses is of particular importance to optimize production and quality. Far-red (FR) light is known to regulate phytochrome-mediated morphological and physiological plant responses, while limited attention has been paid to the benefits of including FR light to indoor plant cultivation. Lettuce (Lactuca sativa L. cv. ‘Tiberius’) plants were grown under a fully controlled environment, in which three different light treatments were arranged. The photosynthetic photon flux density (PPFD) was 200 μmol m−2 s−1 provided by a mixture of red and blue light (red/blue light ratio was 7:1) with peak intensities at 450 nm and 660 nm, respectively. In two of the treatments, 50 μmol m−2 s−1 FR light with peak intensity at 740 nm was supplemented during the day (FR-Day, 16 h) or end of the day (FR-EOD, 1 h). Plant total biomass was increased by 39% and 25% in the FR-Day and FR-EOD treatment, respectively, compared with the control. Adding FR light resulted in 27–49 % larger plant leaf area with an open plant canopy, which facilitated a better light interception and led to higher plant radiation use efficiency (RUE). Although temporarily adding FR light increased net leaf photosynthetic rates by 7–10 %, FR light treatments resulted in a significantly lower chlorophyll and total nitrogen content, as well as lower leaf absorbance, which led to lower maximum leaf photosynthetic rate. Such downregulation had limited effect on plant growth as the net leaf photosynthetic rates in their corresponding growth environments were similar between treatments. The extent of FR light induced leaf physiological modifications was lower in the FR-EOD treatment, in comparison with the FR-Day treatment. Our estimation showed that ˜36% and ˜94% of the enhanced dry mass production in the FR-Day and FR-EOD treatments, respectively, could be attributed to the FR light regulated RUE improvements, the other part enhanced dry mass production might be the consequence of additional light. We conclude that the acclimation process of plant morphology triggered by additional FR light plays a pivotal role for improving the production of indoor cultivated lettuce, and the enhanced production by additional FR light cannot be achieved by adding similar amount of red and blue light.
Tipburn is a physiological disorder of lettuce (Lactuca sativa) and other leafy crops that causes external and internal leaf discolouration and results in serious quality issues for the fresh produce ...industry. Tipburn occurrence is difficult to predict and no completely effective control methods exist. This is compounded by poor knowledge of the underlying physiological and molecular basis of the condition, which appears to be associated with deficiency of calcium and other nutrients. Vacuolar calcium transporters, which are involved in calcium homeostasis in Arabidopsis, show differential expression in tipburn-resistant and susceptible Brassica oleracea lines. We therefore investigated expression of a subset of L. sativa vacuolar calcium transporter homologues, belonging to the Ca2+/H+ exchanger and Ca2+-ATPase classes, in tipburn-resistant and susceptible cultivars. This indicated that some L. sativa vacuolar calcium transporter homologues belonging to these gene classes exhibited higher expression levels in resistant cultivars, whilst others had higher expression in susceptible cultivars or were independent of tipburn phenotype. In addition, some homologues were more highly expressed in symptomatic versus asymptomatic leaves in susceptible cultivars, suggesting that tipburn-induced increases in expression are unsuccessful in conferring resistance and that differential baseline expression of such genes is important for tipburn resistance. Knowledge of individual genes associated with tipburn resistance will improve breeding for such traits and the development of resistant lettuce varieties.
•Ca2+/H+ exchangers and Ca2+-ATPases differentially regulated in tipburn-resistant and susceptible lines.•Increased expression of some of these genes associated with resistance, of others with susceptibility.•Tipburn-induced increases in expression are unsuccessful in conferring resistance.•Tipburn resistance is instead associated with differences in baseline expression levels.
A alface é a hortaliça folhosa mais consumida no mundo. No Brasil, a produção é realizada principalmente nos cinturões verdes das cidades. Dentro desse contexto é preciso avaliar as cultivares de ...alface nas condições edafoclimáticas específicas nas quais serão cultivadas. O trabalho foi realizado com o objetivo de identificar os materiais genéticos de alface tipo crespa mais adaptados à região do Norte de Minas Gerais. O experimento foi conduzido na Unidade de Agroecologia do Instituto Federal de Educação e Ciência e Tecnologia do Norte de Minas Gerais (IFNMG) – Campus Januária, em ambiente aberto em sistema orgânico de cultivo. Foram avaliadas sete cultivares de alface tipo crespa, Isabela, Margarete, Mônica, Valentina, Vanda, Veneranda e Vera, em delineamento experimental de blocos ao acaso com quatro repetições. Na colheita foram avaliados número de folhas, área foliar, massa seca de folhas e caule, comprimento de caule, massa seca de cabeça e produtividade comercial. As cultivares Vera e Veneranda apresentaram potencial produtivo superior em relação as demais cultivares. A cultivar Vera por combinar maiores produtividade e resistência ao pendoamento em relação a cultivar Veneranda é a mais recomendada, e a cultivar Margarete é a menos indicada para o cultivo na estação mais quente no Norte de Minas Gerais.
•RP-UHPLC-ESI-QTOF-MS has proved to be a powerful analytical tool for metabolites profiling.•A total of 171 compounds belonging to several structural classes were tentatively characterized in L. ...sativa.•Lettuce was qualitatively rich in phenolic compounds, especially the cultivar “baby”.•Novel sulfate and amino acid derivatives were tentatively proposed for the first time in lettuce.
Lettuce (Lactuca sativa), a leafy vegetal widely consumed worldwide, fresh cut or minimally processed, constitutes a major dietary source of natural antioxidants and bioactive compounds. In this study, reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) coupled to electrospray ionization-quadrupole-time-of-flight mass spectrometry (ESI-QTOF-MS) was applied for the comprehensive profiling of polar and semi-polar metabolites from three lettuce cultivars (baby, romaine, and iceberg). The UHPLC systems allowed the use of a small-particle-size C18 column (1.8μm), with very fine resolution for the separation of up to seven isomers, and the QTOF mass analyzer enabled sensitive detection with high mass resolution and accuracy in full scan. Thus, a total of 171 compounds were tentatively identified by matching their accurate mass signals and suggested molecular formula with those previously reported in family Asteraceae. Afterwards, their structures were also corroborated by the MS/MS data provided by the QTOF analyzer. Well-known amino acids, organic acids, sesquiterpene lactones, phenolic acids and flavonoids were characterized, e.g. lactucin, lactucopicrin, caftaric acid, chlorogenic acid, caffeoylmalic acid, chicoric acid, isochlorogenic acid A, luteolin, and quercetin glycosides. For this plant species, this is the first available report of several isomeric forms of the latter polyphenols and other types of components such as nucleosides, peptides, and tryptophan-derived alkaloids. Remarkably, 10 novel structures formed by the conjugation of known amino acids and sesquiterpene lactones were also proposed. Thus, the methodology applied is a useful option to develop an exhaustive metabolic profiling of plants that helps to explain their potential biological activities and folk uses.
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•High degradation of antibiotic isoniazid used for tuberculosis treatment Fenton-based processes.•Photo-Fenton by artificial and solar radiation achieves high mineralization of ...isoniazid.•Fenton and photo-Fenton processes generate isonicotinic acid, isonicotinamide,N'-(pyridyl-4-carbonyl)-hydrazide and four new by-products in the first 10 minutes of treatment.•Fenton reaction reduces acute toxicity in D. magna yet inhibits seeds growth in L. sativa, and photo-Fenton performed by artificial radiation reduces toxicity in both test organisms.•Solar photo-Fenton needs prolonged time to generate non-toxic results.
This paper presents the degradation of the most widely used antibiotics for the treatment of tuberculosis, isoniazid (INH), by Fenton, photo-Fenton on bench-scale, and solar photo–Fenton on a pilot scale. The INH dosage in tuberculosis treatment varies according to disease stage, between 300 and 400 mg d−1patient−1, and its excretion range via urine is 50–70% within 24 h. The photodegradation processes were performed with 25 mg L−1 of INH, 10 mg of Fe2+, and 125 mgL−1 of H2O2 for 120 min. The degradation of INH was monitored by HPLC–DAD and dissolved organic carbon (DOC). The degradation by-products were analyzed by UPLC QToF-MS and the toxicity was evaluated by Daphnia magna (acute toxicity) and Lactuca sativa (phytotoxicity). INH removal was higher than 99% at 60 min for Fenton, 10 min for photo-Fenton, and 15 min for solar photo–Fenton. The DOC results indicated that under light irradiation (photo–Fenton and solar photo–Fenton), the mineralization rate was >70%. The nitrite ion analysis indicated the complete oxidation of nitrogen. Besides the main INH degradation by-products, isonicotinic acid, isonicotinamide, and N'-(pyridyl-4-carbonyl)-hydrazide, we detected four unknown by-products by mass spectrometry. The Fenton treatment decreased the toxicity of D. magna by 75% in 15 min, achieving 87% in 60 min of treatment, while the photo–Fenton process conducted with artificial radiation reduced 87% of the toxicity of D. magna and resulted in no significant effect in L. sativa seeds in 15 min (QUV-A 1.29 kJ L−1). However, solar photo-Fenton (QUV-A 3.38 kJ L−1) did not reduce toxicity.
Summary
Lettuce (Lactuca sativa) seeds exhibit thermoinhibition, or failure to complete germination when imbibed at warm temperatures. Chemical mutagenesis was employed to develop lettuce lines that ...exhibit germination thermotolerance. Two independent thermotolerant lettuce seed mutant lines, TG01 and TG10, were generated through ethyl methanesulfonate mutagenesis. Genetic and physiological analyses indicated that these two mutations were allelic and recessive. To identify the causal gene(s), we applied bulked segregant analysis by whole genome sequencing. For each mutant, bulked DNA samples of segregating thermotolerant (mutant) seeds were sequenced and analyzed for homozygous single‐nucleotide polymorphisms. Two independent candidate mutations were identified at different physical positions in the zeaxanthin epoxidase gene (ABSCISIC ACID DEFICIENT 1/ZEAXANTHIN EPOXIDASE, or ABA1/ZEP) in TG01 and TG10. The mutation in TG01 caused an amino acid replacement, whereas the mutation in TG10 resulted in alternative mRNA splicing. Endogenous abscisic acid contents were reduced in both mutants, and expression of the ABA1 gene from wild‐type lettuce under its own promoter fully complemented the TG01 mutant. Conventional genetic mapping confirmed that the causal mutations were located near the ZEP/ABA1 gene, but the bulked segregant whole genome sequencing approach more efficiently identified the specific gene responsible for the phenotype.
Significance Statement
Bulked segregant analysis and whole genome sequencing are more efficient than conventional mapping strategies, which require large populations. To demonstrate the advantages of this approach, we used two independent allelic mutants to identify the causal mutations conferring thermotolerant seed germination in lettuce.
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