Lettuce Seedlings Research Articles

Quantitative trait loci (QTLs) linked with root growth in lettuce (Lactuca sativa) seedlings

In-field variation of transplanted lettuce (Lactuca sativa L.) due to variable soil and environmental conditions is one of the major restrictions in the optimization of production and yield. Marker-assisted breeding for lettuce varieties with a more rapid rooting phenotype has the potential to improve the performance of lettuce transplants. This study aimed to identify traits linked with increased primary root length, lateral root length and lateral root emergence in 14-day L. sativa seedlings from an intra-specific cross (Saladin × Iceberg). In total, 16 significant quantitative trait loci (QTLs) were associated with increased root growth traits that would allow direct introgression of the traits. Six of the QTLs were associated with increased primary root growth, accounting for 60.2% of the genetic variation for the trait. Three QTLs were associated with lateral root growth (38.6% of genetic variation); two QTLs were associated with lateral root length density (27.6% of genetic variation) and three with root number density (33.4% of genetic variation), and two QTLs were associated with mean lateral root length (21.1% of genetic variation). The statistical QTLs were located across 9 different linkage groups (LGs) representing loci on 7 of the 9 L. sativa chromosomes. A combination of restriction fragment length polymorphism (RFLPs) and Kompetitive allele specific PCR (KASPs) markers linked to these rooting traits were identified, which could allow breeders to select for a rapid establishment phenotype.

Effects of melatonin on the sugar metabolism and antioxidative response to excess nitrate stress in lettuce seedlings

Water and soil pollution by nitrate has caused severe impact to environment, especially the inhibition of plant growth due to the excess nitrate stress. Although previous studies reported the melatonin could mitigate injury of plants in response to excess nitrate stress, the alleviation mechanism of melatonin is still unclear. In this study, lettuce seedlings were used as materials, and the main sugar content, sucrose synthesis and metabolism related enzymes as well as ROS metabolism were investigated. There were dramatic changes in sucrose, glucose and fructose content under excess nitrate stress. Exogenous melatonin further increased the sugar content mentioned above, and melatonin increased some sucrose synthesis and metabolism related enzymes under excess nitrate stress, including sucrose phosphate synthase and acid invertase, enhancing sucrose synthesis and metabolism ability. In addition, the content of malondialdehyde and hydrogen peroxide was increased by excess nitrate stress, while inhibited at presence of melatonin. The activities of SOD and POD were also increased by exogenous melatonin in response to excess nitrate stress. In a conclusion, it is suggested that there is a cross-talk between sugar and ROS scavenging pathway under excess nitrate stress, which is enhanced by melatonin, thus promoting the lettuce plants resistance to stress.

Isolation and Characterization of Phosphate Solubilizing Pseudomonas Species and Their Effect on Plant Growth Promotion

Plant growth-promoting rhizobacteria (PGPR) affect plant growth via various direct or indirect mechanisms. These microorganisms are the potential tools for sustainable agriculture. In this study, eight different Pseudomonas strains (PM1 - PM8) isolated from rhizospheric soil were characterized plant growth-promoting characteristics, including indole-3-acetic acid (IAA) and Gibberellin (GA3) production, phosphate solubilization, 1- aminocyclopropane-1-carboxylic acid (ACC) deaminase activity and effects of direct inoculation on plant growth parameters (fresh weight, shoot length). All of these strains have their ability for solubilization of insoluble phosphate depending on pH decrease at the range around pH4 - 5 at 2 days after inoculation. PM1, PM4, PM5 and PM7 species was capable of IAA production and PM4, PM5, PM7 and PM8 species have high activity for production of gibberellin (GA3) hormone. For ACC deaminase activity, PM1, PM3 and PM8 show high activity. Furthermore, all these species have significantly promoted the growth of the lettuce seedling plants for fresh weight and shoot length enhancement, so that these Pseudomonas species could be used as potential bio-fertilizer agents. Production of plant hormone IAA (A) and GA3 (B) from isolated Pseudomonas species.

Vermicompostos como substratos no desempenho de mudas de alface e rúcula

Uma das razões para obter sucesso na horticultura é a produção de mudas de qualidade, utilizando substratos em substituição do solo na formação de mudas. Desse modo, objetivou-se com este trabalho avaliar o desempenho de mudas de alface e rúcula utilizando substratos produzidos com vermicompostos juntamente com a serragem e casca de arroz como agentes condicionantes. Foram realizados dois experimentos em Vilhena, Rondônia, utilizando o delineamento experimental inteiramente casualizado, em esquema fatorial 3x2 com sete repetições, correspondendo a três substratos e duas cultivares, tanto para alface quanto para rúcula. A proporção dos materiais foi de 1:3 do volume total de solo, de esterco de aves e agente condicionante, sendo utilizada a minhoca Vermelha Californiana (Eisenia foetida). Para as cultivares, tanto de alface quanto de rúcula, foram avaliadas a altura de plântulas, diâmetro do colo, massa seca da parte aérea, das raízes e total. Não foi observada diferença significativa entre os tratamentos avaliados em relação a massa seca das raízes de alface da cultivar Crespa, porém para a cultivar Americana, os tratamentos utilizando vermicomposto com agente condicionante a serragem ou casca de arroz, foram superiores ao substrato comercial em relação a massa seca das raízes. Entre as cultivares de rúcula, não foi observado diferença significativa entre os tratamentos sobre as variáveis avaliadas. Portanto, é possível concluir que os substratos produzidos a partir de vermicompostos com serragem e casca de arroz como agentes condicionantes, podem substituir o substrato comercial durante a produção de mudas de alface e rúcula.

BIOCHAR DE SERRAGEM DE EUCALIPTO COMO CONDICIONADOR DE SUBSTRATOS PARA PRODUÇÃO DE MUDAS DE ALFACE

O sucesso na produção de alface (Lactuca sativa L.) começa pela obtenção de mudas com boa qualidade sendo necessário a utilização de substratos que fornecem condições químicas e físicas favoráveis ao desenvolvimento da planta. O reaproveitamento de resíduos na produção de substratos pode ser uma proposta interessante para a produção de mudas. O trabalho objetivou avaliar a influência de biochar produzido a partir da serragem de eucalipto, no desenvolvimento de mudas de alface. O experimento foi conduzido em casa de vegetação com delineamento experimental inteiramente casualizado, com sete tratamentos e três repetições. Utilizou-se a cultivar Grandes Lagos e sete substratos sendo um comercial, Bioplant® (BPL) e seis formados a partir do substrato comercial, Bioplant® + biochar (BC 5, BC 10, BC 15, BC 25, BC 50 e BC 75% m/m). Foram avaliadas as variáveis percentagem de emergência (E), índice de velocidade de emergência (IVE), comprimento da parte aérea (CPA) e sistema radicular (CSR), massa fresca da parte aérea (MFPA) e do sistema radicular (MFSR) e massa seca da parte aérea (MSPA) e do sistema radicular (MSSR), 25 dias após a semeadura. A adição de biochar, ao substrato comercial, Bioplant®, na concentração de 5% em massa, apresentou viabilidade para ser utilizado como condicionador de substrato no desenvolvimento de mudas de alface da cultivar Grandes Lagos.

Performance of agricultural substrates in the production of lettuce seedlings (Lactuca sativa L.)

The production of seedlings for transplanting is one of the most important stage to successful lettuce cultivation. Among the techniques practiced to obtain seedlings of vegetables, stands out using agricultural substrates associated with the cultivation trays. The experimental setup design was in completely randomized with 5 treatments and 6 repetitions.The experiment was carried out in a greenhouse, where were evaluated five commercial substrates (TropstratoHT®, Vivatto Slim Plus®, Tecnomax® , Holambra HS® and Bianchi Power) for the development of lettuce seedlings cv. Lucy Brown. Analyzes were performed to quantify the physical and chemical characteristics of the substrate. It was evaluated Fresh mass of shoots and roots, total fresh mass, dry mass of shoots and roots, total dry mass, stalk diameter, leaf area and leaf number. The results showed that among evaluated substrates, Bianchi Power ® showed be more efficient to seedling lettuce production by influence on the growth and development

Respon Tanaman Selada Merah (Lactuca Sativa L.) Terhadap Larutan Hara (AB Mix ) Pada Instalasi Horizontal Sistem Hidroponik

This study aims to determine the response given by the red lettuce plant to the provision of nutrients in the form of nutrient solution (AB Mix) on the horizontal installation of the hydroponic system. The study was conducted on December 20, 2017 until February 16, 2018 at the PKK Gardens Education Center in Bengkulu province. Seeding process of Red Lettuce Seedlings is carried out for 14 days then transferred to a net pot at the installation in the Greenhouse. Fertilizers with the Fiora A and B Brands are dissolved to be mixed in a nutrient bath with a capacity of 3000 L with a nutrient density of 500 ppm in the Greenhouse to be distributed to the horizontal installation of the hydroponic system inside the Greenhouse. Then growth observations were carried out on 10 plant samples with parameters of leaf length, leaf width, number of leaves, stem height, andstem diameter for 30 days. The results obtained by sample 1-10 have an average growth and development that is not much different. The maximum leaf length and leaf width parameters are in samples 2 and 3. While the highest number of leaf strands in sample 3 is 22 strands with an average of 18 strands and sample 4 has the highest stem height parameter of 3.5 cm with an average height 2.7 cm. The largest stem diameter in sample 4 is 4.1 cm with an average of 3.38 cm. The response of red lettuce after the last week showed symptoms of leaves that are less red with relatively more withered body.

Regulation of melatonin on chlorophyll fluorescence and nitrate accumulation in lettuce seedlings under excess nitrate stress

Excess nitrate stress has become a threat of environmental issues to crop cultivation in China. While measures of remediation and knowledge of the mechanisms underlying excess nitrate stress are limited. Previous studies reported that melatonin could improve the plant resistance to abiotic stress. Thus, we investigated the role of melatonin on the photosynthetic characteristic involved in nitrate assimilation under the excess nitrate stress in lettuce (Lactuca sativa ). Lettuce plants were subjected to moderate excess nitrate stress (160 mM NO3−) with/without supply of 1.0 μM melatonin. Results showed that adding of melatonin decreased the nitrate content both in leaves and roots. Melatonin also dramatically increased the fresh and dry weights in lettuce seedlings. According to the chlorophyll fluorescence parameters, exogenous melatonin inhibited the reduction inφPSII, Fv’/Fm’, qP and rETR caused by excess nitrate stress, while reduced NPQ. In conclusion, exogenous melatonin could decrease the nitrate content in lettuce tissues and enhance the activity of PSII as well as the light energy conversion efficiency for carbon assimilation.

Phytotoxic potential of aqueous leaf extract of Tocoyena formosa and Rudgea viburnoides

ABSTRACT Plants have organic components produced as secondary metabolites able to positively or negatively interfere on normal development of other species. The objective of this research was to determine the phytotoxic effect of aqueous leaf extract from two species Rubiaceae family: Tocoyena formosa and Rudgea viburnoides on the germination and initial development of lettuce (Lactuca sativa L). The extract was obtained from mixing 50 g of fresh leaf and 500 mL of distilled water. The experiment was arranged in completely randomized design for each specie, subjected to five extract concentrations: 0, 25, 50, 75 and 100%; and 4 repetitions of 50 seed each. The bioassays were performed in laboratory at controlled temperature and luminosity during seven days. Results showed that the aqueous extract of both species do not affected the germination and the percent of abnormal lettuce seedlings. R. viburnoides showed no pronounced difference in relation to shoot length and dry biomass; however, the root length was reduced by 85%. The extract of T. formosa at higher concentrations, drastically reduce the dry biomass and length of shoots and roots. Therefore, both species have phytotoxic effect on seedling growth of lettuce being the length root the most affected variable.

Morphoanatomy and Chlorophyll of Lettuce Plants Induced by Rhizobacteria

Lettuce is a consumed crop in the world, and increased yield is a desirable trait, and can be realized with the use of biopromotors, already described in many cultures. The objective of this work was to test the ability of two rhizobacterial isolates P. fluorescens (BRM-3211) and B. pyrrocinia (BRM-3213) to promote anatomical and growth changes in lettuce plants in the seedling stage. The increments promoted by B. pyrrocinia were smaller when using P. fluorescens. The BRM-32111 isolate, promoted increases in leaf area of 133%, 31% and 307% of fresh shoot and root mass, also increased 51% and 143% of aerial and root dry mass. The plants inoculated with BRM-32111 increased in 100% and 68% of the aerial part and radicular compared to the control treatment, and induced alterations in the anatomical characteristics in the root in 74% in the radicular diameter, 20% of the thickness of the cortex, 67% of the exoderme and 171% of the endoderm. In the leaf anatomy, BRM 32111 increased by 18% in the parenchyma expansion, 56% in the number of parenchyma cell layers, 122% adaxial endoderm, 23% epidermis, 174% beam expansion, 37% when compared to control. In this way the use of BRM-32111 influences the growth and morphology of lettuce seedlings.

Nitric oxide alleviates the effects of copper-induced DNA methylation, genomic instability, LTR retrotransposon polymorphism and enzyme activity in lettuce

Copper is an essential element for plant growth, but higher concentration can damage proteins, DNA and lipids. Nitric oxide (NO) is a highly reactive and lipophilic molecule and is functional during plant defense responses. Hence, this study aims to evaluate the role of the exogenous NO treatment (0 µM, 200 µM and 300 µM of sodium nitroprusside) on the DNA damage levels, DNA methylation, retrotransposon polymorphism and enzyme activity in lettuce seedlings grown under the non-stress and copper stressed conditions (200 and 400 µM of CuSO4·7H2O). The inter-retrotransposon amplified polymorphism (IRAP) and couple restriction enzyme digestion-random amplification (CRED-RA) were applied to define the genomic template stability (GTS) levels, DNA methylation, and retrotransposon polymorphism. Copper stress (400 µM) decreased the POD activity as compared to control, whereas combined application of NO (300 µM) and copper increased it as compared to the plants treated with 400 µM copper and without NO. The results of this study highlighted that copper stress increased genomic template instability, DNA methylation and long terminal repeat retrotransposon polymorphism. However, simultaneous treatment of NO and copper caused a decrease in retrotransposon polymorphism and DNA methylation, and an increase in GTS and enzyme activity accompanied it. The results implied that in the presence of excess copper the exogenous NO treatment mitigate the adverse effects of copper stress on the GTS, DNA methylation and retrotransposon polymorphism in lettuce seedlings by increasing antioxidant enzyme activity.

Seedling-lump integrated non-destructive monitoring for automatic transplanting with Intel RealSense depth camera

Non-destructive plant growth parameters measurement is an important concern in automatic-seedling transplanting. Recently, several image-based monitoring approaches have been proposed and potentially developed for several agricultural applications. The presented study proposed and developed a RealSense-based machine vision system for the close-shot seedling-lump integrated monitoring. The strategy was based on the close-shot depth information. Further, the point cloud clustering and suitable algorithms were applied to obtain the segmentation of 3D seedling models. In addition, the data processing pipeline was developed to assess the different morphological parameter of 4 different seedling varieties. The experiments were carried out with 4 different seedling varieties (pepper, tomato, cucumber, and lettuce) and trained under different light conditions (light and dark). Moreover, analysis results showed that there was not significantly different (p < 0.05) found towards light and dark environments due to close-shot near-infrared detection. However, the results revealed that the stem diameter relationship between RealSense and the manual method was found for R2 = 0.68 cucumber, R2 = 0.54 tomato, R2 = 0.35 pepper, and R2 = 0.58 lettuce seedlings. Whereas, the seedling height relationship between RealSense and the manual method was found higher than R2 = 0.99, 0.99, 0.99, and 0.99 for pepper, tomato, cucumber, and lettuce, respectively. Based on the experiment results, it was concluded that the RGB-D integrated monitoring system with the purposed method could be practiced for nursery seedlings most promisingly without high labour requirements in terms of ease of use. The system revealed a good sturdiness and relevance for plant growth monitoring. Additionally, it has the perspective for future practical value to real-time vision servo operations for transplanting robots.

Effects of super-absorbent polymers with different granularities on the physicochemical properties of substrate and the growth of lettuce seedlings

Effects of super-absorbent polymers with different granularities on the physicochemical properties of substrate and the growth of lettuce seedlings

New metabolites produced by endophyte Clonostachys rosea B5 − 2

The endophytic fungus, Clonostachys rosea B5-2 was isolated from mangrove plants and subjected to the one strain many compounds (OSMAC) methodology. By this approach, it was found that modification of the culture media enhanced the production of secondary metabolites by C. rosea B5-2. The apple juice supplemented solid rice media led to significant changes in the secondary metabolism of the fungus, C. rosea B5-2, and induced the production of four new compounds, (-)-dihydrovertinolide (2), and clonostach acids A (3), B (4), and C (5) together with the known compound, (-)-vertinolide (1). The new compound (-)-dihydrovertinolide (2) exhibited phytotoxicity against lettuce seedlings at a concentration of 50 mg L−1.

Survival of Meloidogyne javanica during the summer season under semiarid conditions

One of the survival mechanisms of root-knot nematodes (Meloidogyne spp.) in the absence of host plants during hot and dry summer seasons is anhydrobiosis of second-stage juveniles (J2). Another strategy might be migration of J2 to deeper soil to avoid high soil temperatures and low humidity. Wetting infested soil during such seasons is sometimes suggested as a nematode control method that prevents anhydrobiosis, leading to exhaustion of their energy reserves. Population densities of Meloidogyne javanica at five soil depths (0–50 cm) in irrigated and nonirrigated field plots were estimated during three summer months in two successive years after uprooting infected tomato plants. The number of J2 in the soil was estimated by counting J2 extracted by Baermann funnel extraction and number of root galls on lettuce seedlings grown in the soil samples. Significant factors for J2 survival were number of days after plant removal and soil depth, probably due to lower maximum daily soil temperatures and higher water contents at depth. Irrigation did not consistently affect the number of extracted J2 or root galls. No obvious evidence of J2 migration from the upper to deeper soil layers or nematode-control effects of the irrigation were observed.

Caffeine: The Allelochemical Responsible for the Plant Growth Inhibitory Activity of Vietnamese Tea (Camellia sinensis L. Kuntze)

The present study aimed to examine the phytotoxic potential of seven Vietnamese tea samples based on the specific and total activity of caffeine and tea extracts on test plants. The sandwich method results indicated that the inhibitory effect of tea samples on the radicle and hypocotyl growth of lettuce seedlings was dependent on the concentration and type of tea samples, and also the presence of agar soluble allelochemicals. Among the seven tea samples, the leachates from Vinatea-green tea showed the highest inhibition on the radicle growth of lettuce seedlings with 50% suppression at 0.12 mg dry leaves/mL of agar. Caffeine concentration in tea samples analyzed by high-performance liquid chromatography (HPLC) varied from 20.7 to 38.2 µg/mL of dry leaves. The specific activity (EC50 value) of pure caffeine was 75 µg/mL, and the highest total activity of caffeine estimated in Vinatea-green tea was 0.51 [no unit]. Caffeine from green and oolong tea may be considered as one of the contributors to the inhibitory activity of the crude extract. Moreover, the phytotoxicity of pure caffeine and aqueous tea extracts was highly selective on the growth of different plant species. The concentration of caffeine detected from tea farm soil ranged from 0.137 to 0.145 µg/g soil. The results indicated that caffeine might be considered as a promising allelochemical from Vietnamese tea and can be a good candidate for weed management.

Effects of exogenous putrescine on the ultrastructure of and calcium ion flow rate in lettuce leaf epidermal cells under drought stress

The alleviation effects of exogenous putrescine treatment on the ultrastructure of and calcium ion flow rate in lettuce (Lactuca sativa L.) leaf cells under drought stress were studied. Lettuce seedlings were treated with foliar sprays of 0.1 mM putrescine for 8 days, after which drought stress was simulated by using 10% polyethylene glycol 6000. The morphological characteristics of the seedlings and the calcium ion flow rate across stomatal guard cells were subsequently determined, and the leaf cell ultrastructure was observed via transmission electron microscopy. Under drought stress, the morphological characteristics of the seedlings decreased, and calcium ion influx was predominant in the guard cells. In addition, compared to that under control conditions, the stomatal density under drought stress conditions increased significantly, the open/closed stoma ratio was lower, and the degree of stomatal opening was smaller. Exogenous putrescine sprays effectively reduced the stomatal density, increased the degree of stomatal opening, and increased the proportion of open stomata. In addition, the chloroplasts became round in shape, the thylakoid structure became blurry in appearance, the number of starch grains decreased, many osmium granules were produced, and plasmolysis occurred in the mesophyll cells. However, the chloroplasts were elongated, the thylakoid structure was clear, the starch grains were abundant, few osmium granules were produced, and plasmolysis did not occur. The above results show that, by altering the leaf cell ultrastructure as well as the flow rate and direction of calcium ions in guard cells, exogenous putrescine effectively improves the drought tolerance of lettuce.

The Kinetics and Mechanisms for Photodegradation of Nitrated Polycyclic Aromatic Hydrocarbons on Lettuce Leaf Surfaces: An In Vivo Study.

Insights into the environmental fates of nitrated polycyclic aromatic hydrocarbons (NPAHs) in edible vegetables are of great significance for better evaluating human exposure to NPAHs through the dietary pathway. In this work, a fluorescence quenching method using graphene quantum dots as a fluorescent probe was first applied for the in vivo determination of 9-nitroanthracene (9-NAnt) and 1-nitropyrene (1-NPyr) adsorbed on the leaf surfaces of living lettuce (Lactuca sativa L.) seedlings. Moreover, the photolysis kinetics and mechanisms of the two adsorbed NPAHs were discussed. The photodegradation kinetics followed the pseudo-first-order equation, and the photodegradation half-life of 1-NPyr (7.4 ± 0.2 h) was greater than that of 9-NAnt (2.3 ± 0.1 h). Anthraquinone and pyrenediones were identified to be the main photolytic products of 9-NAnt and 1-NPyr, respectively. Intramolecular rearrangement was the most reasonable mechanism for the NPAH photolysis. The photolysis-driven degradation exhibited a key role in scavenging NPAHs from the vegetable leaf, indicating the reduction of NPAH transportation in the food chain.

Phytochemical analysis and effect of the essential oil of Psidium L. species on the initial development and mitotic activity of plants.

The use of allelopathic compounds is an alternative for weeds control, since they present low toxicity when compared with the synthetic herbicides, that may cause several damages, as the contamination of the environment. Our objective was to determine the chemical composition and allelopathic properties of the essential oils of Psidium cattleianum, P. myrtoides, P. friedrichsthalianum, and P. gaudichaudianum on the germination and root growth of Lactuca sativa and Sorghum bicolor, and to evaluate their action on the cell cycle of root meristematic cells of L. sativa. The main compound found in all the studied species was (E)-caryophyllene (P. cattleianum-23.4 %; P. myrtoides-19.3%; P. friedrichsthalianum-24.6% and P. gaudichaudianum-17.0%). The different essential oils were tested at different concentrations on L. sativa and S. bicolor, reducing germination, germination speed index, and root and shoot growth of lettuce and sorghum seedlings. The cytotoxicity and aneugenic potential of these oils were evidenced by the reduction of the mitotic index and increase of the frequency of chromosomal alterations in L. sativa. The essential oils of the species of Psidium studied have potential to be used in weeds control.

A new function of the biocontrol bacterium Lysobacter enzymogenes LE16 in the mineralization of soil organic phosphorus

To evaluate the functions of a new biocontrol bacterium, Lysobacter enzymogenes LE16, in the mineralization of soil organic phosphorus (P) and in the stimulation of plant P uptake and plant growth. Liquid culture, soil incubation, and pot experiments were used to study phosphatase production, inorganic P release from lecithin and soil organic P compounds, and the P uptake and growth of lettuce seedlings induced by L. enzymogenes LE16. This bacterium hydrolyzed lecithin by the release of acid, neutral and alkaline phosphatases in culture solutions with a pH ranging from 4.0 to 10.0 at 12–36 °C. The hydrolysis reactions were unaffected by NH4+-N, NO3−-N or urea at equal N concentrations but were promoted by low inorganic P. Bacterial inoculation significantly decreased the organic P but increased the water-soluble P and Olsen P in the soil. Compared to the use of chemical fertilizers alone, the P uptake, biomass, and economic yield of lettuce increased by 16.41%, 11.58%, and 11.30%, respectively, with an increase in soil Olsen P in the L. enzymogenes LE16 plus chemical fertilizer treatment. Environmental adaptation and phosphatase production could be the mechanisms involved in soil P mineralization and plant pathogen suppression by L. enzymogenes LE16. This is the first demonstration of a new use of L. enzymogenes LE16 in agriculture beyond plant protection.