•Soilless culture requires optimization of nutrient uptake to maximize yield and quality of crop.•A problem in soilless culture is unbalanced nutrient uptake due to variation in nutrients ...absorption.•Amino acids biostimulants have been used to improve plant growth, yield and nutrient use efficiency.•Data collected from two cultivars were compared to each other.•Biostimulants was efficient in enhancing yield and nutritive value which depends on cultivar.
Biostimulants containing amino acids and minerals have been used commercially to promote plant growth, yield and nutritive value of food crops. Limited studies on biostimulants application are available on lettuce production in soilless systems. This research was conducted to determine the effects of foliar application of amino acids biostimulants (Perfectose™, liquid) on yield and leaf quality of two lettuce cultivars, romaine and iceberg, under soilless conditions. Plants of both lettuce cultivars were sprayed with three different concentrations of Perfectose at 0 (control, only water), 2 and 4 ml L−1. Perfectose was applied twice during the crop cycle. Foliar application of Perfectose resulted in increasing lettuce fresh yield by 25.7 and 39%, dry yield by 28.6 and 55.3% and leaf number per head by 18.8 and 22.8% over control for iceberg and romaine cultivars, respectively. In comparison to untreated plants, application of Perfectose at the rate 4 ml L−1 had increased leaf nutrient contents of N, P, K and Mg, phenols, flavonoids and antioxidant activity by 20.5, 25.1, 19.8, 58.5, 28.4, 30.6 and 35.7%, respectively over both cultivars. Romaine cultivar has produced higher fresh and dry yields, leaf number, leaf N, P, K, Mg, total phenols and flavonoids contents and antioxidant activity in comparison to iceberg cultivar especially at 4 ml L−1 rate. However, the iceberg cultivar was more responsive (in terms of percentage change) to Perfectose application by generally enhancing leaf N, K, total phenols and flavonoids contents and antioxidant activity than in romaine cultivar. Therefore, application of amino acids stimulant Perfectose is considered efficient in enhancing the yield and nutritive value of lettuce and the efficiency is dependent on used cultivar under soilless conditions.
The complex and enormous diversity of microorganisms associated with plant roots is important for plant health and growth and is shaped by numerous factors. This study aimed to unravel the effects of ...the soil type on bacterial communities in the rhizosphere of field-grown lettuce. We used an experimental plot system with three different soil types that were stored at the same site for 10 years under the same agricultural management to reveal differences directly linked to the soil type and not influenced by other factors such as climate or cropping history. Bulk soil and rhizosphere samples were collected 3 and 7 weeks after planting. The analysis of 16S rRNA gene fragments amplified from total community DNA by denaturing gradient gel electrophoresis and pyrosequencing revealed soil type dependent differences in the bacterial community structure of the bulk soils and the corresponding rhizospheres. The rhizosphere effect differed depending on the soil type and the plant growth developmental stage. Despite the soil type dependent differences in the bacterial community composition several genera such as Sphingomonas, Rhizobium, Pseudomonas, and Variovorax were significantly increased in the rhizosphere of lettuce grown in all three soils. The number of rhizosphere responders was highest 3 weeks after planting. Interestingly, in the soil with the highest numbers of responders the highest shoot dry weights were observed. Heatmap analysis revealed that many dominant operational taxonomic units were shared among rhizosphere samples of lettuce grown in diluvial sand, alluvial loam, and loess loam and that only a subset was increased in relative abundance in the rhizosphere compared to the corresponding bulk soil. The findings of the study provide insights into the effect of soil types on the rhizosphere microbiome of lettuce.
The effects of sonication, sanitizers and sodium dodecyl sulfate (SDS) on the quality of fresh-cut Iceberg and Romaine lettuce were examined. Lettuce samples were treated for 1 min with and without ...ultrasound with one of the following solutions: tap water, chlorine, Tsunami, and a combination of Tsunami with 1 g/L SDS. Washed samples were packed under modified atmosphere conditions and stored at 4 °C for up to 14 days. Changes in headspace gases, texture, color, tissue damage, visual quality, and natural flora were determined. The O2 concentrations and CO2 accumulation in Romaine lettuce were not significantly different among the treatments. In Iceberg lettuce, a lower O2 and high CO2 content in the headspace of samples treated with Tsunami and Tsunami + SDS were recorded. After 14-day storage, the tissue damage expressed by electrolyte leakage, total color difference, firmness, and total aerobic plate counts were not significantly different among treatments in two types of lettuce samples. Treatment of Iceberg lettuce with sonication in combination with Tsunami or Tsunami + SDS did not degrade quality compared to samples treated with chlorine alone, whereas for Romaine lettuce, chlorine-treated samples had a significantly higher overall quality score than that from the other treatments.
•The use of a surfactant at low concentration did not cause additional quality changes.•None of the treatments had a detrimental effect on the color of packaged lettuce.•The use of sanitizers effectively reduced the initial count of natural flora.
Ametryne is an herbicide applied to sugar cane cultures to prevent the emergence of weeds. It is a persistent compound that percolates ground and surface water thus impacting aquatic communities. In ...this study, we evaluated microbial activity in soil with increased concentrations of ametryne solution and commercial Microgeo biofertilizer. The soil subject to analysis was obtained from a sugar cane cultivation area. The concentration used in the experiment was ametryne 12 mu g/L and 1 % of biofertilizer. It was used with the Bartha and Pramer respirometric method to quantify CO sub(2) production and determine microbial activity. Complimentary phytotoxicity tests with Lactuca sativa seeds after respirometry experiments were conducted in the soluble fraction of the soil. According to the results, the addition of biofertilizer promoted microbial activity in the presence of ametryne and reduced ametryne phytotoxicity for Lactuca sativa seeds. Thus, Microgeo biofertilizer can potentially improve biodegradation of ametryne through both bioaugmentation and bioestimulation.
Long-term fumigation with pure phosphine at low-temperature injures lettuce and the injury is likely caused by a potential accumulation of CO sub(2). In this study, iceberg and romaine lettuce were ...stored hermetically in fumigation chambers with and without absorbents for CO sub(2) and ethylene for 3 days at 2 super(o)C as a simulation of long-term fumigation to determine the effects of the absorbents on accumulations of CO sub(2) and ethylene and postharvest quality of lettuce. In the absence of absorbents, CO sub(2) level increased from 0.08% at the start to 3.36% at the end of the 3-day hermetic storage. No accumulation of ethylene was detected. Hermetic storage resulted in significant CO sub(2) injuries to both iceberg and romaine lettuce and quality degradation as compared with the controls at 14 days after treatment. In the storage with absorbents, the CO sub(2) level remained low throughout the storage and ethylene was undetectable, and the CO sub(2) injury level was the same or lower than the control. Lettuce quality scores were either the same or better than lettuce in the control. Our findings suggest that the accumulation of CO sub(2) alone caused injuries associated with long-term phosphine fumigation and CO sub(2) absorbent has the potential to prevent such injuries.
Survival and internalization characteristics of Escherichia coli O157:H7 in iceberg, romaine, and leaf lettuce after inoculation of leaf surfaces and soil were determined. A five-strain mixture of E. ...coli O157:H7 in water and cow manure extract was used as an inoculum for abaxial and adaxial sides of leaves at populations of 6 to 7 log and 4 log CFU per plant. The five strains were individually inoculated into soil at populations of 3 and 6 log CFU/g. Soil, leaves, and roots were analyzed for the presence and population of E. coli O157:H7. Ten (4.7%) of 212 samples of leaves inoculated on the adaxial side were positive for E. coli O157:H7, whereas 38 (17.9%) of 212 samples inoculated on the abaxial side were positive. E. coli O157:H7 survived for at least 25 days on leaf surfaces, with survival greater on the abaxial side of the leaves than on the adaxial side. All 212 rhizosphere samples and 424 surface-sanitized leaf and root samples from plants with inoculated leaves were negative for E. coli O157:H7, regardless of plant age at the time of inoculation or the location on the leaf receiving the inoculum. The pathogen survived in soil for at least 60 days. Five hundred ninety-eight (99.7%) of 600 surface-sanitized leaf and root samples from plants grown in inoculated soil were negative for E. coli O157:H7. Internalization of E. coli O157:H7 in lettuce leaves and roots did not occur, regardless of the type of lettuce, age of plants, or strain of E. coli O157:H7.
•The wastewater supplemented with mineral fertilizers was satisfactory in growing hydroponic lettuce.•The nutrients absorption in the culture with wastewater and mineral fertilizers was similar to ...absorption with drinking water and mineral fertilizers.•Treated domestic effluent didn’t meet the nutritional demands of the lettuce.•The wastewater supplementation with mineral fertilizers provided up to 4 times in fresh mass, in comparison to its use without supplementation.•The growth curve was increased for plants cultivated with wastewater.
The aim of this research was to evaluate the nutrient absorption and the fresh mass of lettuce plants cultivated using domestic wastewater in a hydroponic system during winter and summer seasons. The hydroponic system used was the Nutrient Film Technique with three treatments: 1) drinking water and chemical fertilizers (T1): 2) wastewater supplemented with chemical fertilizers (T2): and 3) only wastewater (T3) in a completely randomized experimental design with four replicates. The wastewater was previously characterized before being used in the treatments in order to quantify the need for nutrient supplementation in the T2 treatment. To determine the fresh mass, dry mass and nutrient absorption, three whole plant samples of each plot were collected at 1, 7, 14 and 21 days after transplanting. The nutrient absorption occurred according to a growing polynomial function for all treatments and most of the elements throughout the two cycles of the crop, except for potassium and magnesium in the T3 treatment in the winter crop. The results of fresh mass of the plant, pH and electrical conductivity of nutrient solutions were submitted to 2-way ANOVA, considering winter and summer as the first factor and treatments as the second one. A significant interaction between the factors for fresh mass and electrical conductivity was observed, and for that reason the average were submitted to Tukey test (p < 0.05%). For T1 and T2 treatments, significant differences were found between the average of the fresh mass of winter and summer, with higher values in winter. For the T3 treatment, no difference was found between the evaluated periods, but there was a significant difference in relation to the other treatments in both periods. The plants of this last treatment had lower fresh mass, less accumulation of nutrients and visual symptoms of nutritional deficiency. Under the experimental conditions, it was concluded that there was no difference in the nutrient absorption between the T1 and T2 treatment, but in the T3 treatment, the absorption was slower and smaller, demonstrating that it is necessary to supplement the wastewater with nutrients.
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