Lettuce Seedlings Research Articles

Growth analysis of lettuce seedlings adding green or far-red to an optimized red and blue LED light spectrum

Growth analysis of lettuce seedlings adding green or far-red to an optimized red and blue LED light spectrum

Effect of microplastics on dry matter content in Lactuca sativa L.

Plastics are commonly used in every field of life due to their ease of use and economics. If the plastic wastes are not disposed of properly, they form microplastics by breaking down into smaller particles with decomposition. Microplastics are chemical substances in polymer structure. They are difficult to dissolve in nature and require a long time. Microplastics, that spread to the environment in various ways, cause pollution and negatively affect organisms and ecosystems. 
 This study aimed to determine the effects of microplastics and the combined impact of microplastics and Cd on dry matter content (the ratio of dry mass to fresh mass of an organ), which is the one of the major plant traits for plant growth, in lettuce (Lactuca sativa L.). Five experiment sets were designed by using Simila variety lettuce seedlings, including (1) control, (2) 1.5 % microplastic (3) 2.5 % microplastic, (4) 1.5 % microplastic and 200 ppm Cd solution and (5) 2.5 % microplastic and 200 ppm Cd solution added. The polyethylene mulch pieces (2,5 mm x 4 mm) were used as microplastics. Results showed that the polyethylene microplastic addition to the soil significantly reduced aboveground and belowground DMCs of lettuce seedlings. Concentration of the microplastics in the soil was also effective on DMC. The Cd addition to the soils, which contain microplastics, a bit increased the DMC.

PEMANFAATAN HIDROPONIK AJB SEBAGAI MEDIA BUDIDAYA TANAMAN SELADA (Lactuca sativa L) DI PEKARANGAN RUMAH

The AJB hydroponic system is a type of hydroponics found by managers from Mataram who use a substrate or planting medium in the form of sand. Hydroponics generally allows plant roots to sink in water or nutrient solution, but this can cause the roots of planted plants to decay because they are always in water. In the AJB hydroponic system, the roots of the lettuce plant will not be inundated directly because the water will mix with the sand substrate as the planting medium and the water itself will stagnate under the pot to the limit of the holes in the AJB hydroponic pot. The nutrients used in this system are a mixture of nutrients a and b or AB mix which is given through a pipe in the middle of the pot. This is so that the distribution of nutrients from the middle can be spread evenly. The pipe in the middle also has a hole at a height close to the surface of the soil so that the nutrients provided can reach and stimulate the roots to grow to the bottom where the nutrients are stagnant. In this study, the aspect observed was the growth in height of lettuce leaves/day which was calculated manually using a ruler by providing 1 liter of nutrients per each pot at the beginning and providing nutrients once every 3 days thereafter with a volume of 0.28 liters/each pot. The results of this study were an average growth of 0.286 cm/day for all samples or lettuce seedlings from pot 1 to pot 7.

Assessment of transcriptional reprogramming of lettuce roots in response to chitin soil amendment.

Chitin soil amendment is known to improve soil quality, plant growth and stress resilience, but the underlying mechanisms are not well understood. In this study, we monitored chitin's effect on lettuce physiology every two weeks through an eight-week growth period, analyzed the early transcriptional reprogramming and related metabolomic changes of lettuce, in response to crab chitin treatment in peat-based potting soil. In commercial growth conditions, chitin amendment still promoted lettuce growth, increased chlorophyll content, the number of leaves and crop head weight from week six. The flavonoid content in lettuce leaves was altered as well, showing an increase at week two but a decrease from week six. Transcriptomic analysis showed that over 300 genes in lettuce root were significantly differentially expressed after chitin soil treatment. Gene Ontology-term (GO) enrichment analysis revealed statistical overrepresentation of GO terms linked to photosynthesis, pigment metabolic process and phenylpropanoid metabolic process. Further analysis of the differentially expressed genes (DEGs) showed that the flavonoid pathway was mostly upregulated whereas the bifurcation of upstream phenylpropanoid pathway towards lignin biosynthesis was mostly downregulated. Metabolomic analysis revealed the upregulation of salicylic acid, chlorogenic acid, ferulic acid, and p-coumaric acid in chitin-treated lettuce seedlings. These phenolic compounds (PCs) mainly influence the phenylpropanoid biosynthesis pathway and may play important roles in plant defense reactions. Our results suggest that chitin soil amendments might activate induced resistance by priming lettuce plants and promote lettuce growth via transcriptional changes.

Strategy to Minimize Plant Accumulation of Contaminants of Emerging Concern: Alternation between Treated Wastewater and Freshwater Irrigation

Treated wastewater (TWW) is increasingly used for agricultural irrigation in arid and semiarid areas, but it can introduce contaminants of emerging concern (CECs) into the food chain, posing a potential risk to human health. While many studies have shown that plants can accumulate some CECs, so far little effort has been made to explore mitigation strategies. This study tested the concept of alternating between TWW with conventional freshwater for irrigation to minimize CEC accumulation in plants. Tomato and lettuce seedlings were first cultivated in CEC-containing hydroponic solutions for 3 weeks, and then in CEC-free media for another 3 weeks. The plant tissues contained elevated concentrations of perfluorobutanesulfonate, perfluorobutanoic acid, perfluorohexanoic acid, carbamazepine, and fluoxetine ranging from 42.1 to 2724.2 ng/g (dry weight). However, after being transferred to CEC-free media, most CEC levels decreased by over 75%, attributed to plant metabolism, growth dilution and back release to culture media. This proof-of-concept study suggested that using TWW during the early part of the growing season may effectively minimize CEC accumulation. Such hybrid irrigation schemes have a great prospect for expanding the safe reuse of TWW and other lower-quality water sources in agriculture and should be further evaluated under field conditions.

What is the optimal fertigation start time and frequency in lettuce seedlings?

Although lettuce is one of the most important vegetable crops cultivated in Brazil, producers conduct seedling production empirically, as there are no published reports on the optimal start time and management strategy for seedling fertigation. The present aimed to assess the influence of fertigation management on the growth, physiological aspects and nutritional status of lettuce seedlings and to determine the optimal fertigation start time and frequency. Two experiments were conducted, each with a randomized block design and six repetitions. The first consisted of six treatments, namely six fertigation start times at 0, 3, 6, 9, 12, and 15 d after emergence (DAE), and the second consisted of five treatments, representing different application frequencies at 3, 4, 5, 6, and 7 d intervals. The assessment of nutrient accumulation levels and biometric and physiological characteristics of the seedlings were performed after transplanting. Fertigation start times significantly affected 14 of the 18 variables assessed, particularly the number of leaves, shoot dry weight, leaf area, initial chlorophyll fluorescence, and P, K, Ca, Mg, and S accumulation. The best results for ten variables were obtained when fertigation began at emergence, with values 17.77 - 35.63% higher than those at fertigation onset at 15 DAE. Application frequency only influenced chlorophyll content and N, P, K, and S accumulation, with optimal results obtained at 3 - 6 d intervals. Beginning fertigation at plant emergence favors dry weight production, nutrition and photosynthesis and shortens the production time of lettuce seedlings. The optimal start time for lettuce seedling fertigation is at emergence, with application performed every 6 d.

Diagrammatic scale for evaluation of Bremia lactucae sporulation in lettuce seedlings

In disease assessment, the use of diagrammatic scales provides a standard reference point for comparison. There is still no precise and accurate scale for the evaluation of sporulation intensity of downy mildew in lettuce seedlings. The objective of this study was to propose a diagrammatic scale for the evaluation of downy mildew severity in lettuce seedlings. Thirty lettuce seedlings with different sporulation intensities were used to develop the proposed diagrammatic scale. Solaris lettuce cultivar was sown, and fifteen days after sowing, inoculations occurred using distilled water, the pathogen sporangia, and Tween 20. The monitoring of disease development was performed daily.When the first sporulation appeared on the cotyledonaryleaves,the proposed scale was verified to meet the minimum and maximum levels of disease severity. Two evaluators verified the accuracy, precision and performed the estimation of the sporulation and reproducibility using a scale. The images obtained are important in the standardization of a scale to identify resistant, tolerant and susceptible plants to downy mildew. Furthermore, it allows validating a diagrammatic scale of sporulation intensity of B. lactucae in lettuce seedlings. Thus, it is the diagrammatic scale developed in the work will guide future research to accelerate the detection of mildew severity in lettuce seedlings.

Aqueous Extracts of Four Medicinal Plants and Their Allelopathic Effects on Germination and Seedlings: Their Morphometric Characteristics of Three Horticultural Plant Species

Allelopathy is a biological phenomenon of synthesizing and excreting compounds that can affect the growth of various organisms, i.e., plant species. The aim of this work was to investigate the possible allelopathic influence of aqueous extracts, obtained from plant species chia (Salvia hispanica L.), black cumin (Nigella sativa L.), wormwood (Artemisia absinthium L.), and nettle (Urtica dioica L.), on the seed germination growth and morphometric characteristics of pepper (Capsicum annuum L.), spinach (Spinacia oleracea L.) and lettuce (Lactuca sativa L.) seedlings in laboratory conditions. Pepper, spinach, and lettuce seedlings were treated with aqueous extracts of chia, nettle, wormwood, and black cumin of different concentrations (2.5, 5 and 10%, respectively). The aqueous extracts were prepared according to the method developed by Norsworthy and the qualitative and quantitative analysis of phenolic compounds in aqueous extracts were performed using ultra-performance liquid chromatography electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). Phytochemical composition of chia aqueous extracts showed the highest content (above the 1 mg L−1) of epicatechin, quinic acid, caffeic acid, esculetin and cinnamic acid in the comparison with others from the total of 19 detected chemical compounds. In aqueous extracts of black cumin, there were six compounds detected in content above 1 mg L−1, i.e., epicatechin, quinic acid, caffeic acid, esculetin, cinnamic acid, and kaempferol. The same compounds were the most abundant in wormwood extracts, along with gallic acid. Epicatechin and esculetin were only two compounds detected in aqueous extract of nettle in concentration higher than 1 mg L−1. According to the results of this study, only the treatment of spinach seeds with chia aqueous extract in concentration of 2.5% before germination stimulates the germination of spinach seeds, and wormwood herbs and chia extracts in concentrations of 2.5 and 5% stimulate the germination of lettuce seeds and the growth of hypocotyl and radicle length of developed seedlings. The treatment of pepper and lettuce seeds with aqueous extract of nettle in concentration of 10% completely inhibited seed germination.

Effect of Priestia endophytica on the metabolites accumulation in chicory and lettuce plants cultivated in vitro

The influence of the culture medium without bacterial cells, obtained after the cultivation of endophytic bacteria Priestia endophytica UCM B-5715, on the growth and synthesis of some metabolites in lettuce and chicory seedlings under in vitro conditions was studied. Bacteria were cultivated in liquid LB medium at 37 ºC for 24 h with periodic stirring. The culture fluid was separated from the cell biomass. For preparing the test solution, the supernatant was sterilized by filtration through a filter with a pore diameter of 0.2 µm (Sartorius, Minisart) and diluted with sterile distilled water. The 20% culture fluid (30 µl/plant) was applied to 3-day-old seedlings. In 28 days root and shoot weights of treated chicory plants were 54.3 ± 6.9 and 260.0 ± 20.2 mg, respectively (8.0 ± 0.7 and 91.4 ± 7.0 mg for the control plants). Total flavonoid content and antioxidant activity increased only in chicory plants after the addition of the test solution. Significant changes in the metabolism of treated plants were detected. In the treated lettuce plants asparagine content increased compared to the control (90 vs 22 µg/g, p < 0.1). The median content of fructose was also higher in treated lettuce and chicory plants (1469 vs 73 µg/g and 2278 vs 1051 µg/g). Therefore, the use of culture fluid obtained after the cultivation of P. endophytica UСM B-5715 stimulated the growth of lettuce and chicory plants, affecting the synthesis of some compounds in single-treated plants. These results indicate the potential of compounds excreted during bacterial growth to create natural growth stimulators.

Seed priming by application of Microbacterium spp. strains for control of Botrytis cinerea and growth promotion of lettuce plants

The abusive use of chemical pesticides to control plant diseases has caused the loss of soil biodiversity as well as the emergence of resistance by plant pathogens. This effect has forced an urgent search for other environmentally sustainable alternatives that serve to control plant pathogens safely and efficiently. In this sense, the search for new biopesticides is currently a booming field within the field of agro-biotechnology. Volatile compounds produced by plant-associated microorganisms represent a diverse resource to promote plant growth and health. In this work, a collection of 29 strains of the genus Microbacterium from the composting of plant remains was studied. The objective was to determine whether the production of volatile compounds of microbial origin could contribute to the mitigation of symptoms caused by the fungus Botrytis cinerea (gray mold) as well as contribute to the lettuce plant growth in seedbeds. It should be noted that in both the B. cinerea inhibition and seed priming assays, the microorganisms did not come into direct contact with either the pathogen or the seeds. In all cases, incubation was carried out in a closed environment to expose the seeds to the microbial volatiles. Five strains capable of inhibiting the in vitro growth of B. cinerea at levels greater than 30% were pre-selected. Only 3 of these 5 strains, identified as M. aerolatum, M. foliorum and M. profundi showed positive results in the in vitro germination promotion test in lettuce seeds, increasing the radicle weight at levels close to 45%. These strains finally were tested in planta, showing two of them significant palliative effects of B. cinerea and promoting the development of lettuce seedlings both at aerial and root levels.

Light Intensity during Green-Leaf Butterhead Lettuce Propagation Influences Yield and Carotenoids at Harvest

Controlled environment agriculture (CEA) operations must increase resource-use efficiency, yield, and phytonutrient concentrations to remain competitive. Carotenoids are phytonutrients of interest due to their purported health promoting effects. Their content is impacted by environmental controls, including lighting. Light-use efficiency increases with greater planting density, which is highest during seedling production. This creates the opportunity to raise light intensity during seedling production to improve growth characteristics and phytonutrient concentrations at harvest. Therefore, the objective of this research was to quantify the extent to which light intensity influences carotenoid accumulation in green butterhead lettuce seedlings, and if differences remain at harvest. Lettuce ‘Rex’ (Lactuca sativa L.) seedlings were grown under fluorescent lighting with intensities of 60, 100, 200, 400, or 600 µmol·m−2·s−1 with a 24-h photoperiod. After 14 days, seedlings were transplanted into raft hydroponic systems in a common greenhouse environment and grown for 21 days. At transplant and final harvest, tissue samples were collected and stored at −80 °C for phytonutrient analysis. Carotenoids, β-carotene, lutein, neoxanthin, zeaxanthin, and violaxanthin, and chlorophylls a and b were quantified using high-performance liquid chromatography (HPLC). We observed a 475% fresh mass enhancement in seedlings grown under 400 versus 60 µmol·m−2·s−1, with a 174% improvement persisting to final harvest. Higher seedling light intensities also generally increased leaf numbers in seedlings and at final harvest, as well as seedling carotenoid concentrations. Final harvest carotenoid concentrations generally decreased with increasing light intensity. Thus, producers should be cognizant that seedling light intensity strongly influences seedling and finished production yield, morphology, and carotenoid content.

Phytotoxicity of Quillaja lancifolia Leaf Saponins and Their Bioherbicide Potential.

Weeds are major threats to the integrity of agricultural and natural environments due to their invasive and competing potential. Bioherbicides are substances based on natural compounds that are biodegradable and often have low residual effects. Plant species able to produce and release phytotoxic compounds may represent effective bioherbicide sources. Leaves of Quillaja lancifolia D.Don (formerly Q. brasiliensis (A.St.-Hil. & Tul.) Mart.) produce water-soluble specialized metabolites of the saponin class that could be evaluated for phytotoxic activity and potential as natural herbicides. This study was conducted to examine the impacts of Q. lancifolia total saponins aqueous extract (AE) at 4 and 10% (w/v) and of two combined reverse-phase chromatography purified saponin fractions (QB) at 1 and 2% (w/v) on morpho-physiological parameters of Lactuca sativa (lettuce) and Echinochloa crus-galli (barnyardgrass) in pre- and post-emergence bioassays. QB was only tested in pre-emergence assays. In pre-emergence bioassays, the germination rate and germination kinetics were determined. Post-emergence evaluations included effects on seedling morphology, root and shoot length, dry mass, and chlorophyll content. Osmotic potential and pH analyses ruled out roles for these factors in the observed responses. AE had a high inhibitory impact on the germination of both lettuce and barnyardgrass. QB at 1% and 2% (w/v) significantly decreased the growth of lettuce seedlings germinated in its presence by more than 10-fold. Phytotoxic effects on the post-emergence growth of lettuce, especially at the highest concentration tested of AE (10% w/v), was also observed. The presence of quillaic acid-based triterpene saponins in AE and QB was confirmed using different analytical methods. Therefore, both saponin-enriched fraction and aqueous extracts of Q. lancifolia inhibited tested plant growth and development. The water solubility of saponins and the availability of a sustainable source of these molecules from the leaves of cultivated young Q. lancifolia plants make them attractive candidates for use as bioherbicides.

Coir-Based Growing Media with Municipal Compost and Biochar and Their Impacts on Growth and Some Quality Parameters in Lettuce Seedlings

The purpose of this study was to develop substrates with little or no peat by combining coir-based growing media with municipal compost and/or acacia biochar, two locally produced renewable resources, and to assess their effects on lettuce seedling emergence and growth, as well as their content in photosynthetic pigments and total phenols. Two experiments were carried out, the first with six mixes using compost and biochar blended with perlite, pine bark, and blonde peat to adjust some physicochemical characteristics. The mixes of coir: compost: pine bark: blonde peat (73:12:5:10, v/v) and coir: compost: biochar: blonde peat (73:12:10:5, v/v) had physicochemical characteristics closer to or within the normal range of the substrates. The presence of 12% compost and 10% biochar in the mixtures had no adverse effect on lettuce seed germination and cumulative seed emergence, which ranged from 90 to 99%. The seedling growth in those mixes was vigorous and higher than in other mixtures. Coir-based growing media with municipal solid waste compost and compost plus biochar can reduce the use of peat to a percentage of 5–10% v/v and the use of 17–22% v/v of locally produced renewable resources. In addition, mixtures affected the total phenol content in the lettuce leaves. Future research is needed to assess the behavior of seedlings after their transplantation.

Potential use of Terasi, an Indonesian traditional fermented seafood paste, to provide healthy lettuce (Lactuca sativa L.) seedling

Terasi paste consists of plant nutrients and microorganisms that potentially improve the health of plant seedlings. We evaluated the effects of terasi paste on seed germination, seedling growth, and root rot disease severity caused by Fusarium oxysporum f.sp. lactucae (FOL) in lettuce. Terasi paste was tested at four different weights (i.e., 0.00 g [T0], 1.00 g [T1], 2.50 g [T2], and 5.00 g [T3]) in the 100 g nursery soil. The results showed that lettuce seeds from T1 and T2 treatments were fully germinated, as observed for the T0 treatment. However, 40.0% of lettuce seeds from T3 treatment failed to germinate. Thus, 1.00 g and 2.50 g terasi applications in the 100 g soil did not affect lettuce seed germination. Moreover, T1 and T2 treatments tended to improve the shoot and root biomass of lettuce seedlings over T0 treatment, while T3 treatment showed the opposite effects. Following FOL infection, the lettuce seedlings from T2 and T3 treatments had 31.1% significantly lower disease severity than those from the T0 treatment. Therefore, T2 treatment (i.e., 2.50 g terasi application in the 100 g soil) imparts maximum health-promoting benefits to lettuce seedlings.

Efeito materno na tolerância à termoinibição em sementes de alface

Abstract The objective of this work was to evaluate the occurrence of the maternal effect on thermotolerance in lettuce (Lactuca sativa) seeds, as well as to find an enzymatic marker for this trait in lettuce seedlings. Seeds from the Everglades thermotolerant cultivar, the Verônica susceptible cultivar, and their reciprocal hybrids were used. For each cultivar and reciprocal hybrid, germination percentage and vigor (germination speed index) tests were carried out at 20 and 32°C. Thermotolerance was defined as the capacity to germinate at 32°C. To obtain markers that could be associated with thermotolerance, enzymatic tests were performed. The bands of the electrophoretic enzymatic extracts were quantified using the ImageJ software. The hybrids behaved similarly to their female genitors. When cultivar Verônica was the female genitor, hybrid seeds did not germinate at high temperatures and showed a lower expression of the esterase enzyme. However, when the female genitor was the Everglades cultivar, hybrids showed a high germination at high temperatures and a greater esterase expression. Therefore, there is a maternal effect on tolerance to thermoinhibition in lettuce seeds, and the esterase enzyme can be used as a selective marker to identify homozygous progenies for this trait.

EMERGÊNCIA DE SEMENTES E DESENVOLVIMENTO DE MUDAS DE ALFACE EM DIFERENTES SUBSTRATOS

INTRODUCTION: The production of lettuce seedlings is one of the most important steps in the production system. The substrate used in the production of lettuce seedlings plays a key role, and the quality depends on its physical structure and chemical composition. OBJECTIVE: Evaluate the effects of different substrates on germination and development of Verônica variety lettuce seedlings. METHODS: The experiment was carried out in Seedling Nursery Vale Verde, located in the municipality of Patrocínio, state Minas Gerais, Brazil, average altitude of 945 meters, geographic coordinates 18°54'14.4" south latitude and 46°59'40.9" west longitude. For this experiment, polystyrene trays were used. The experimental design was completely randomized, in a factorial scheme 3 x 1 x 7, and 28 seeds per plot, being considered for evaluation 12 seedlings of each plot. The substrates used were: phenolic foam, coconut fiber and compost. Data were subjected to analysis of variance and, subsequently, the means of treatments were subjected to multiple comparison analysis, by Tukey's test. RESULTS: There was a highly significant difference for emergence speed index, root size, leaf size, and significant difference for number of leaves. Germination, dry mass and green mass, on the other hand, did not show any significant difference. CONCLUSION: The phenolic foam substrate provided greater speed of emergence. The new world composite and coconut fiber substrate features a greater number of leaves and root size. The largest leaves and consequently the accumulation of green mass and dry mass were obtained in seedlings cultivated in the coconut fiber substrate. KEYWORDS: : emergency; hardwood; source; transplant; nursery.

Plant growth-enhancing traits of rhizobacteria isolated from brinjal, okra, and leaf mustard

Exploring new plant-associated rhizobacteria and reintroducing them to the crop-soil environment is among the strategies to reverse the declining quality of the agricultural soil environment. A total of 340 isolates were recovered from the rhizospheres of okra (Abelmoschus esculentus), leaf mustard (Brassica juncea), and brinjal (Solanum melongena). From among the total, 155 isolates (45.59%) were diazotrophs, and 122 (35.88%) and 127 (37.35%) were isolates with the solubilising activity of phosphate and potassium, respectively. Thirteen of the most promising isolates were identified by gas chromatography for their cellular fatty acid methyl esters: Escherichia vulneris (TC19), Klebsiella pneumoniae (BA5, SA19, SB22), Pantoea ananatis (TC22), Pseudomonas aeruginosa (BA46), Pseudomonas putida (BA29, BA37, SC5, SC14), Salmonella bongori (BC17), Salmonella enterica (BB2), and Shigella dysenteriae (BA16). Three Pseudomonas strains viz. P. aeruginosa BA46 and P. putida BA37 and SC5 were selected after enhancing root elongation and vigour of lettuce seedlings. The American lettuce growth performance in the non-circulating hydroponic system was established. The inoculation with rhizobacteria strains, SC5 and BA46, stimulated shoot and root biomass over uninoculated control plants. The inoculation of lettuce plants with isolates BA37, BA46 and SC5, produced significantly longer roots compared to uninoculated control plants. This study indicates the potential use of the strains BA46 and SC5 as candidates for the formulation and production of hydroponic nutrient solution fortified with beneficial bacteria.

Biodegradation and reduction of toxicity of Azo Trypan Blue dye by Amazonian strains of gasteroid fungi (Basidiomycota).

Amazonian strains of Cyathus spp. and Geastrum spp. were studied for the ability to discolor the trypan blue azo dye and reduce its toxicity. Discoloration of trypan blue dye (0.05%) was evaluated in solid and aqueous medium over different periods. The reduction of dye toxicity after treatment was assessed by seed germination and the development of lettuce seedlings (Lactuca sativa L.) and toxicity test in Artemia salina (L.) larvae. All evaluated strains showed the potential to reduce the color intensity of trypan blue dye. Cyathus strains reached 96% discoloration, and C. albinus and C. limbatus also reduced dye toxicity. Geastrum strains showed a high efficiency degree in color reduction, reaching 98% discoloration, however, the by-products generated during the process presented toxicity and require further investigation. For the first time, Amazonian strains of gasteroid fungi degrading trypan blue are reported, some even reducing its toxicity. Thus, making them promising sources of enzymes of interest to bioremediation scenarios involving synthetic dyes.

Technical feasibility of the use of sludge from the water treatment plant in lettuce production

The sludge generated in water treatment plants (WTP sludge), despite having physicochemical characteristics with agricultural potential, is a solid waste discarded in landfills. This research aimed to: 1) evaluate the technical feasibility of WTP sludge in substitution of commercial substrates in the production of lettuce seedlings; 2) to evaluate the yield commercial, in the municipality of Arapiraca, semiarid region of the state of Alagoas - Brazil. The research was carried out in two stages: 1) seedling production in greenhouse in 4 x 4 x 5 factorial arrangement, with four sludge doses (0, 20, 40 and 60%), four commercial substrates (Pindstrup®, Vida Verde®, Bioplant 434® and Bioplant 401®) and five cultivars (Veneranda, Camila, Elba, ‘Vitória Verdinha’ and Diva); 2) seedlings produced at field level were used in 3 x 3 x 5 factorial arrangement, in which Pindstrup treatments and 60% sludge dose were excluded, as they did not promote seedling emergence. In the 1st experiment, it was observed linear reduction of seedling quality index with the addition of sludge. In the 2nd experiment, the average yield was 5.4 Mg ha-1, in which 20% sludge dose promoted the highest values, being recommended for lettuce production in the semiarid region of Alagoas.

Ameliorative effects of foliar potassium nitrate on the growth, physiological, and stomatal properties of lettuce plants under salinity stress

The restorative effects of foliar potassium nitrate spraying on morphological, physiological, and stomata properties of salt-affected lettuce (Lactuca sativa L.) cv. Yedikule plants were investigated. Lettuce seedlings grown under saline irrigation water constituted by NaCl levels with 50, 100, 150, and 200 mM were sprayed with foliar KNO3 at 500 mg L−1 after 30-day-old plants. Salinity stress adversely influenced plant growth and physiological parameters. Fresh plant biomass, leaf area per plant, and leaf number were limited at 100 mM NaCl and above. Leaf temperature, chlorophyll content, dry matter, turgor loss, and electrolyte leakage were enhanced under saline conditions; however, salinity diminished leaf relative water content. Foliar KNO3 spraying improved the physiologic and stomata traits of salt-affected lettuce plants rather than plant growth. The electrolyte leakage was increased by increasing salinity and KNO3 spraying, whereas the relative injury was lower in the plants treated with foliar KNO3. An increase in stomata density was detected up to 100 mM NaCl, while stomata length and width were gradually decreased. Salinity and foliar KNO3 resulted in more frequent stomata number up to 100 mM NaCl, but it was surprisingly reduced at higher NaCl levels. Lettuce plants could grow up with irrigation water salinity of 100 mM and foliar KNO3 with 500 mg L−1 could regulate the adverse effects of salinity on the physiological characteristics up to 100 mM NaCl.