Lettuce Shoot Research Articles

Variability, plot size and border effect in lettuce trials in protected environment

ABSTRACT The variability within rows of cultivation may reduce the accuracy of experiments conducted in a complete randomized block design if the rows are considered as blocks, however, little is known about this variability in protected environments. Thus, our aim was to study the variability of the fresh mass in lettuce shoot, growing in protected environment, and to verify the border effect and size of the experimental unit in minimizing the productive variability. Data from two uniformity trials carried out in a greenhouse in autumn and spring growing seasons were used. In the statistical analyses, it was considered the existence of parallel cultivation rows the lateral openings of the greenhouse and of columns perpendicular to these openings. Different scenarios were simulated by excluding rows and columns to generate several borders arrangements and also to use different sizes of the experimental unit. For each scenario, homogeneity test of variances between remaining rows and columns was performed, and it was calculated the variance and coefficient of variation. There is variability among rows in trials with lettuce in plastic greenhouses and the border use does not bring benefits in terms of reduction of the coefficient of variation or minimizing the cases of heterogeneous variances among rows. In experiments with lettuce in a plastic greenhouse, the use of an experimental unit size greater than or equal to two plants provides homogeneity of variances among rows and columns and, therefore, allows the use of a completely randomized design.

Application of biosolids drives the diversity of antibiotic resistance genes in soil and lettuce at harvest

High-throughput quantitative polymerase chain reaction (PCR) of antibiotic resistance genes (ARGs) was used to profile the composition and diversity of ARGs in biosolid-amended soil and in lettuce roots and shoots. Biosolid application significantly increased the ARGs in soil and influenced the soil antibiotics resistome mainly through exogenous introduction. Four dominant ARGs occurred in sterilized and water-washed leaves, namely catB8, php, vanB and str, which accumulated to >50% of total abundance. Nine subclasses of ARGs were determined in both sterilized and water-washed leaves, and they were shared ARGs among soil, roots and shoots. This suggests that the ARGs in ready-to-eat lettuce were mainly located in endophytes and the internal route may contribute more to the ARGs in routinely consumed raw lettuce. Moreover, a previously unsuspected shift in multridrug ARGs to root and shoot compartments due to biosolid application was discovered. These results reveal that biosolid application drives the evolution and dissemination of ARGs in the soil-plant system.

Pengaruh Konsentrasi Kalian Nitrat pada Media Vermikompos Terhadap Kandungan Hara Trubus Selada (Lactuca Sativa L.)

<em>The content of nitrogen and potassium in vermicompost generally low, i.e. less than two percent, so that still require the addition of another source to meet crop requirement.� Potassium nitrate to form the ions K<sup>+</sup> and NO<sub>3</sub><sup>?</sup>� after disolved in water so as to be readily available to plants.� The study aims to determine the effect of the addition of potassium nitrate in vermicompost me</em>dium to the concentration of nutrients in the shoot of lettuce.� Research conducted in the form of pot experiment.� The treatment consists of 12 levels of concentration or nutrient solution electrical conductivity with the addition of potassium nitrate.� The results of experiment indicated that the concentrations of P and K in plant shoot tissue were significantly increased linearly with the provision of KNO<sub>3</sub>.� The concentration N, Ca, Mg, S, Na, Fe, Mn, Cu, Zn, Al and B in shoot tissue of plants is not affected KNO<sub>3</sub>.

Uptake and Accumulation of Pharmaceuticals in Overhead- and Surface-Irrigated Greenhouse Lettuce.

Understanding the uptake and accumulation of pharmaceuticals in vegetables under typical irrigation practices is critical to risk assessment of crop irrigation with reclaimed water. This study investigated the pharmaceutical residues in greenhouse lettuce under overhead and soil-surface irrigations using pharmaceutical-contaminated water. Compared to soil-surface irrigation, overhead irrigation substantially increased the pharmaceutical residues in lettuce shoots. The increased residue levels persisted even after washing for trimethoprim, monensin sodium, and tylosin, indicating their strong sorption to the shoots. The postwashing concentrations in fresh shoots varied from 0.05 ± 0.04 μg/kg for sulfadiazine to 345 ± 139 μg/kg for carbamazepine. Root concentration factors ranged from 0.04 ± 0.14 for tylosin to 19.2 ± 15.7 for sulfamethoxazole. Translocation factors in surface-irrigated lettuce were low for sulfamethoxalzole, trimethoprim, monensin sodium, and tylosin (0.07-0.15), but high for caffeine (4.28 ± 3.01) and carbamazepine (8.15 ± 2.87). Carbamazepine was persistent in soil and hyperaccumulated in shoots.

Assessing phytotoxicity of trace element-contaminated soils phytomanaged with gentle remediation options at ten European field trials

Gentle remediation options (GRO), i.e. in situ stabilisation, (aided) phytoextraction and (aided) phytostabilisation, were implemented at ten European sites contaminated with trace elements (TE) from various anthropogenic sources: mining, atmospheric fallout, landfill leachates, wood preservatives, dredged-sediments, and dumped wastes. To assess the performance of the GRO options, topsoil was collected from each field trial, potted, and cultivated with lettuce (Lactuca sativa L.) for 48days. Shoot dry weight (DW) yield, photosynthesis efficiency and major element and TE concentrations in the soil pore water and lettuce shoots were measured.GRO implementation had a limited effect on TE concentrations in the soil pore water, although use of multivariate Co-inertia Analysis revealed a clear amelioration effect in phytomanaged soils. Phytomanagement increased shoot DW yield at all industrial and mine sites, whereas in agricultural soils improvements were produced in one out of five sites. Photosynthesis efficiency was less sensitive than changes in shoot biomass and did not discriminate changes in soil conditions.Based on lettuce shoot DW yield, compost amendment followed by phytoextraction yielded better results than phytostabilisation; moreover shoot ionome data proved that, depending on initial soil conditions, recurrent compost application may be required to maintain crop production with common shoot nutrient concentrations.

Acute Toxicity and Cytotoxicity of Pereskia aculeata, a Highly Nutritious Cactaceae Plant.

Pereskia aculeata is a Cactaceae plant with valuable nutritional properties, including terrific amounts of protein, minerals, vitamins, and fiber. However, P. aculeata is reported to contain antinutrients and alkaloids in its leaves. In addition, in a study on growth and development, Wistar rats fed with P. aculeata and casein as protein source grew less than the control group (fed with casein only). Therefore, in this study, we evaluated, for the first time, the oral acute toxicity of P. aculeata in rats and also the cytotoxicity behavior of the plant on lettuce seeds. The acute toxicity research was carried out using dried P. aculeata ethanolic extract, in three different doses, administered by gavage to 24 female Wistar rats. The rats were then examined for signs of toxicity, food intake, body weight, and fecal excretion fluctuations, as well as histopathological alterations, using eight different body tissues. The acute toxicity study did not show any difference among the groups in either clinical evaluation or histopathological analyses. For the cytotoxicity study, dried P. aculeata ethanolic extract was applied on lettuce seeds in five different concentrations. These seeds were evaluated for germination, root and shoot length, and mitotic index. The results show that P. aculeata extract affects lettuce root and shoot growth, but not germination or mitotic index. In conclusion, the acute toxicity on rats and the cytogenotoxicity on lettuce of P. aculeata are neglectable, validating the potential of this plant to be used as a functional food.

Mitigating cadmium accumulation in greenhouse lettuce production using biochar.

Greenhouse experiments were conducted to investigate the influence of rice straw biochar (RSB) on soil cadmium (Cd) availability and accumulation in lettuce. The RSB was applied either in bands or broadcast in the test site of four greenhouses with soil Cd concentrations ranging from 1.70-3.14μgg-1. Biochar doses applied in bands were half of those broadcast. The Cd levels in the shoots of lettuce were observed to be reduced by up to 57% with increasing RSB application rate (0, 6, 12, 18tha-1). Following RSB application, shoot Cd concentrations of lettuce were reduced to below the Chinese threshold value set for food, and hazard quotients for Cd associated with vegetable consumption were reduced from 0.70-1.11 to 0.42-0.65. A decrease in soil bulk density (11%) and increases in water holding capacity (16%), available phosphorus (30%), available potassium (197%), and lettuce yield (15%) were observed after RSB application. Multiple linear regression analysis suggested that the soil extractable Cd level (but not biomass dilution) and soil bulk density, as influenced by RSB addition, were the dominant contributors to the shoot Cd levels in lettuce and lettuce yield, respectively. These results highlight the potential for RSB to mitigate the phytoaccumulation of Cd and thereby to reduce human exposure from vegetable consumption. Application of biochar in band, rather than broadcasting over the entire area, represents an opportunity to halve the biochar cost while retaining a good remediation effect.

Growth of wheat and lettuce and enzyme activities of soils under garlic stalk decomposition for different durations.

Garlic (Allium sativum L.) stalk is a byproduct of garlic production that is normally thought of as waste but is now considered a useful biological resource. It is necessary to utilize this resource efficiently and reasonably to reduce environmental pollution and achieve sustainable agricultural development. The effect of garlic stalk decomposed for different durations was investigated in this study using wheat (Triticum aestivum L.) and lettuce (Lactuca sativa var. crispa L.) as test plants. Garlic stalk in early stages of decomposition inhibited the shoot and root lengths of wheat and lettuce, but it promoted the shoot and root lengths in later stages; longer durations of garlic stalk decomposition significantly increased the shoot and root fresh weights of wheat and lettuce, whereas shorter decomposing durations significantly decreased the shoot and root fresh weights; and garlic stalk at different decomposition durations increased the activities of urease, sucrase and alkaline phosphatase in soil where wheat or lettuce was planted. Garlic stalk decomposed for 30 or 40 days could promote the growth of wheat and lettuce plants as well as soil enzyme activities. These results may provide a scientific basis for the study and application of garlic stalk. © 2016 Society of Chemical Industry.

Immobilization and bioavailability of heavy metals in greenhouse soils amended with rice straw-derived biochar

Pollution of greenhouse soils and crops by heavy metals as a result of annual application of large amounts of pesticides and fertilizers is of great concerns. We investigated the effect of biochar (BC) as a potential immobilizing medium for cadmium (Cd) by assessing Cd bioavailability, fractions, and uptake of metals by lettuce plants in metal-contaminated greenhouse soils. Experiments were conducted in two typical vegetable greenhouses displaying different levels of heavy metal pollution (GH1, lightly heavy-metal-polluted greenhouse; GH2, heavily heavy-metal-polluted greenhouse), in Wuhan City suburbs, Hubei Province, China. For each greenhouse site three replicates of each of three levels of BC (B0, 0tha−1; B10, 10tha−1; B20, 20tha−1) were arranged in a randomized complete block design. The application of BC increased soil pH and soil organic matter and changed Cd fractions in the soil. The exchangeable Cd fraction decreased and there was an increase in the oxide- and organic-bound and residual fractions with the application of BC, implying that BC application could immobilize the Cd in greenhouse soil. The rates of Cd immobilization in soil increased with the amount of BC applied. The exchangeable Cd fractions in soils amended with B10 decreased by 45–62% and in soils amended with B20 by 66–89% compared to the control. The addition of BC reduced the concentration of Cd in lettuce shoots in the lightly heavy-metal-polluted soils, but in the heavily heavy-metal-contaminated soils it had either no effect, or promoted Cd absorption by lettuce shoots. Total Cd measured in lettuce tissues did not decrease with the addition of BC when compared to the control, as there was increased accumulations of lettuce biomass with biochar application.

Lettuce (Lactuca sativa‘Webb’s Wonderful’) shoot and root growth in different grades of compost and vermicomposted compost

Lettuce (<i>Lactuca sativa</i>‘Webb’s Wonderful’) shoot and root growth in different grades of compost and vermicomposted compost

USING OF AGRICULTURAL DRAINAGE WATER FOR LETTUCE PRODUCTION IN HYDROPONIC SYSTEM

The objectives of the present work were to study the effects of irrigation with Agricultural Drainage Water (ADW) on lettuce (Lactuca sativa L.) yield, quality, and water use efficiency (WUE) with hydroponic system. Five mixing treatments of Agricultural drainage water (ADW) with fresh water (mean normal irrigation water) were used T1:(100% agricultural drainage water), T2:(75% agricultural drainage water mixed with 25% fresh water), T3:(50% agricultural drainage water mixed with 50% fresh water), T4:(25% agricultural drainage water mixed with 75% fresh water), and T5:( 100% fresh water). Nutrient Film Technique (NFT) hydroponic system was developed with five pipes PVC and nutrient solution added in rates: 12.5%, 25%, 50%, 75%, and 100% from standard nutrient solution for T1, T2, T3, T4, and T5, respectively. The results showed that lettuce plant can be produced in 50 days from planting to harvest by (NFT) hydroponic system. Moreover irrigation by using T3 had effectively increased the yields of green and dry matter. The higher Lettuce yields obtained with trend T3 > T5 > T2 > T4 > T1. And plants irrigated with T3 used water more efficiently than those irrigated with other water treatments. The higher water use efficiency (WUE) 39.96 kg/m3 was obtained with T3 and the lower value 16.67 with T1. On the other hand mineral nutrient contents in dry matter of N, P, K, and Ca contents were obviously higher in plants irrigated with T5 than with other water treatments. Heavy metals (Cd, Ni, Cr and Pb) contents in Lettuce shoots were higher in plants irrigated with T3 than those irrigated with other water treatments, but their levels did not reached the maximum allowed levels by FAO for edible crops.

Bioguided fractionation and isolation of phytotoxic compounds from Apium graveolens L. aerial parts (Apiaceae)

The phytotoxic activity of celery (Apium graveolens L.) was tested on germination and seedling growth of Lactuca sativa (lettuce). Bioactive compounds were isolated and identified by spectral data. Methanol extract of celery aerial part showed a significant phytotoxic effect on lettuce. Thus, this extract was divided into hexane and methanol fractions. Bioassay-directed of these two fractions led to the isolation and characterization of six secondary metabolites which included three phthalides (senkyunolide A, (3S)-butylphthalide and sedanolide), two furanocoumarins (bergapten and scopoletin) and one phenylpropanoid (p-hydroxyphenethyltrans-ferulate). Among these compounds, senkyunolide A was the most toxic on lettuce germination and shoot growth. However, p-hydroxyphenethyl trans-ferulate was the most toxic on root growth.

Allelopathic Activity of Dehulled Rice and its Allelochemicals on Weed Germination

In this study, the allelopathic potential of dehulled rice, rice, and hulls of rice on germination of weeds was evaluated in laboratory. Phenolic acids in growth media of these plants were also identified and quantified using HPLC. Identified allelochemicals were reversely tested for phytotoxic effects on germination and seedling growth of barnyardgrass, lettuce, radish and rice. The results showed that the inhibitory effects of dehulled rice were stronger than those of hulls and rice. Dehulled rice caused 66.7% and 50.6% reduction in radish root length and lettuce shoot height, respectively. Dehulled rice showed strong inhibitory effects on root length of lettuce and shoot height of radish while hulls and rice exhibited stimulation. Regarding phenolic identification, vanillin and vanillic acid were detected as allelochemicals in root exudates of rice and tested plants. The results revealed that most of the vanillin and vanillic acid treatments showed high inhibitory effects on germination rates and seedling growth of lettuce and radish, high stimulatory activity on root elongation of rice. Vanillic acid (100 ppm and 200 ppm), vanillin (100 ppm) and their mixture (200 ppm) completely inhibited survival of lettuce. The findings indicate the allelopathic potential of dehulled rice which can be used for identification of more phytotoxins to produce bioherbicides in agricultural practices.

Allelopathic Activity of Dehulled Rice and its Allelochemicals on Weed Germination

In this study, the allelopathic potential of dehulled rice, rice, and hulls of rice on germination of weeds was evaluated in laboratory. Phenolic acids in growth media of these plants were also identified and quantified using HPLC. Identified allelochemicals were reversely tested for phytotoxic effects on germination and seedling growth of barnyardgrass, lettuce, radish and rice. The results showed that the inhibitory effects of dehulled rice were stronger than those of hulls and rice. Dehulled rice caused 66.7% and 50.6% reduction in radish root length and lettuce shoot height, respectively. Dehulled rice showed strong inhibitory effects on root length of lettuce and shoot height of radish while hulls and rice exhibited stimulation. Regarding phenolic identification, vanillin and vanillic acid were detected as allelochemicals in root exudates of rice and tested plants. The results revealed that most of the vanillin and vanillic acid treatments showed high inhibitory effects on germination rates and seedling growth of lettuce and radish, high stimulatory activity on root elongation of rice. Vanillic acid (100 ppm and 200 ppm), vanillin (100 ppm) and their mixture (200 ppm) completely inhibited survival of lettuce. The findings indicate the allelopathic potential of dehulled rice which can be used for identification of more phytotoxins to produce bioherbicides in agricultural practices.

Elevated Carbon Dioxide Level Suppresses Nutritional Quality of Lettuce and Spinach

Rising global CO2 levels are a major factor that impacts not only the environment but also many plant functions including growth, productivity and nutritional quality. The study examined the impact of elevated [CO2] on nutritional quality and growth characteristics of lettuce (Lactuca sativa) and spinach (Spinacia oleracea). Elevated [CO2] decreased the concentration of many important nutrients including nitrogen (protein), potassium and phosphorus in the edible parts of both lettuce and spinach. The nitrogen concentration in lettuce shoots was reduced by more than 30% at elevated [CO2] compared to the plants grown at ambient level of CO2. Similarly the concentration of a number of micronutrients including sulfur, zinc, copper and magnesium, was depressed in lettuce shoots. Although the total phenolic content and antioxidant capacity were higher in lettuce at elevated CO2, they were not affected in spinach. The photosynthetic activity was variable among the plant species while there was no increase in the carbon accumulation in these plants at elevated [CO2]. However, there was significant reduction in the leaf stomatal conductance in both lettuce and spinach in response to higher [CO2], which is likely affect both water loss from the leaves and their photosynthetic activity. The results indicate a broad adverse impact of rising [CO2] on the nutritional quality of commonly consumed leafy vegetables namely, lettuce and spinach.

Crisphead lettuce under influence of soil conditioner, organic fertilizers and liming

Lettuce is considered the main leafy vegetable crop in Brazil. High amounts of mineral and organic fertilizers are applied to soils during lettuce growth. There is a need of data concerning the effect of organic fertilizers and liming, including soil conditioners. Few studies were carried out verifying effects of soil conditioners, organic fertilizers and liming on lettuce production. The aim of this work was to test a soil conditioner composed of humic material, organic fertilizers and liming on “iceberg” lettuce production. The experiment was conducted at Federal University of Lavras, Minas Gerais State, Brazil, from March to July, in greenhouse conditions. The experimental design was completely randomized in a factorial scheme 5x3x2. Five doses of soil conditioner (0, 20, 40, 100, 200 L ha-1), 3 types of fertilizers (organic compost, chicken manure and mineral), with or without liming were studied. Fresh and dried biomass, commercial fresh and dried biomass, plants height, circumference of lettuce head, number of leaves, and dried root weight yield were evaluated. Chicken manure rendered the higher lettuce shoot commercial fresh weight and circumference than the other evaluated fertilizers. In general the soil conditioner did not influence lettuce production. The use of liming was very important on lettuce production when mineral fertilizers were used.

Evaluation of Lettuce Genotypes for Salinity Tolerance

Lettuce is one of the most commonly used salad vegetables and considered to be a relatively salt-sensitive crop. Salinity is a major constraint to crop production in all important lettuce growing regions of the United States, and the water quality problem is exacerbated by climate change. To identify salt-tolerant lettuce genotypes, 178 cultivars and germplasm accessions (56 butterhead, 39 crisphead, 35 romaine, 33 leaf, and 15 wild types) were selected from a preliminary screening of more than 3800 genotypes, and tested for salinity tolerance in sand cultures under greenhouse conditions. Plants were grown in Hoagland nutrient solution, either with or without 30/15 mm NaCl/CaCl2, and leaf fresh and dry mass (FM and DM), chlorophyll index, and maximal photochemical efficiency (Fv/Fm) were measured 4 weeks after plants were transplanted. Generally, salinity decreased lettuce shoot FM and DM, increased DM/FM ratio and chlorophyll index, and had no effect on Fv/Fm. Some lettuce varieties showed salt tolerance (less than 15% reduction in FM), such as PI 342515, PI 358020c, ‘Morgana’, ‘Amerika’ (butterhead), ‘Laura’ (crisphead), PI 289023, PI 273577, PI 278066, PI 177425 (romaine), PI 171676a, PI 177423, PI 342477, and PI 358018b (leaf). The results indicate that lettuce genotypes differ greatly in their salt sensitivity, which could be useful for growers to choose cultivars and for breeders to improve lettuce adaptation to salinity stress.

Evaluation of plant growth regulatory activity of furofuran lignan bearing a 7,9':7',9-diepoxy structure using optically pure (+)- and (-)-enantiomers.

The plant growth regulatory activity of furofuran lignan (7,9':7',9-diepoxylignan) was evaluated by employing optically pure synthesized (+)- and (-)-enantiomers. (+)-Sesamin possessing a 3,4-methylenedioxy group on the aromatic rings and 7-aryl structure showed growth promotion activity against lettuce roots (EC50 = 0.50 mM); on the other hand, growth inhibitory activity was observed against lettuce shoots (EC50 = 0.38 mM). Against ryegrass shoots, (-)-sesamolin, which has 3,4-methylenedioxy groups on the aromatic rings and a 7-acetal structure, was effective in showing growth inhibitory activity (EC50 = 0.23 mM). Different activity levels were observed between (+)- and (-)-enantiomers. It was assumed that the 3,4-methylenedioxy group on the aromatic ring was more potent for the plant growth regulatory activity.

Phytotoxic Substance with Allelopathic Activity in Brachiaria decumbens

The grass Brachiaria decumbens becomes naturalized and quickly dominant in non-native areas. It was hypothesized that phytotoxic substances of plants may contribute to the domination and invasion of the plants. However, no potent phytotoxic substance has been reported in B. decumbens. Therefore, we searched for phytotoxic substances with allelopathic activity in this species. An aqueous methanol extract of B. decumbens inhibited the growth of roots and shoots of cress (Lepidium sativum), lettuce (Lactuca sativa), timothy (Phleum pratense) and ryegrass (Lolium multiflorum) seedlings. The extract was then purified using chromatographic methods and a phytotoxic substance with allelopathic activity was isolated and identified by spectral analysis as (6R,9S)-3-oxo-α-ionol. These results suggest that this compound may contribute to the allelopathic effect caused by the B. decumbens extract and may be in part responsible for the invasion and domination of B. decumbens. Two other Brachiaria species, B. brizantha and a Brachiaria hybrid were also confirmed to contain (6R,9S)-3-oxo-α-ionol. Therefore, this compound may play an important role in the phytotoxicity of the Brachiaria species.

Effects of Low-Level Aqueous Hydrogen Sulfide and Other Sulfur Species on Lettuce (Lactuca sativa) Seed Germination

Low concentrations of aqueous hydrogen sulfide (H2S) can stimulate growth of some crops. However, it is not clear whether H2S provides crops with only sulfur and whether other sulfur compounds have similar beneficial effects. Therefore, impacts of solutions of sodium sulfate (Na2SO4), sodium sulfite (Na2SO3), sodium sulfide (Na2S), ferrous sulfide (FeS), and H2S at 0.01–1 mM were assessed on 5-day lettuce seed germination. Results showed that 0.01 mM H2S solution significantly increased lettuce shoot elongation by 40 percent (to 43.6 mm from 31.0 mm in the control), whereas 0.1 mM increased elongation by 24 percent to 38.5 mm. Only a slight 10 percent increase was observed in 0.1 mM Na2SO4, suggesting that ameliorative impact of H2S on plant growth was not a result of providing sulfur nutrient. Other sulfur solutions, however, inhibited lettuce germination and elongation to varying extents, hinting that H2S might work as a signal molecule in regulating plant cellular activities.