Lettuce Biomass Research Articles

Bio-Based Solutions for Agriculture: Foliar Application of Wood Distillate Alone and in Combination with Other Plant-Derived Corroborants Results in Different Effects on Lettuce (Lactuca Sativa L.).

Simple SummaryBio-stimulants are showing growing success and are gradually replacing synthetic fertilizers in agriculture. Wood distillate (WD), also known as wood vinegar or pyroligneous acid, is a by-product of biomass pyrolysis and is increasingly used as a bio-stimulant for crop production. The purpose of this work was to test two types of WD utilizations: (i) pure WD (from BioDea®) and (ii) WD combined with 3% soy lecithin and 5% flavonoid-rich wood glycolic extract (BF; BioDea Flavor®), at concentrations of 0.25% and 0.50%. Our results indicate that foliar applications of both WD and BF increased chlorophyll content, biomass, and starch content in the treated lettuce, while WD, at a concentration of 0.50%, also increased glucose and fructose content. All the treatments were found to be safe, as neither of them showed a significant increase in the content of potentially toxic elements (PTEs) in lettuce.Bio-stimulants are showing growing success and are gradually replacing synthetic fertilizers in agriculture. Wood distillate (WD), also known as wood vinegar or pyroligneous acid, is a by-product of biomass pyrolysis and is increasingly used as a bio-stimulant for crop production. This study investigated whether weekly foliar applications of 0.25% and 0.50% WD have a differential effect on the chlorophyll and sugar content as well as biomass production in lettuce (Lactuca sativa L.). Moreover, the additional beneficial effect from the addition of corroborants of plant origin such as 3% soy lecithin and 5% flavonoid-rich wood glycolic extract to WD (BF) was investigated. Moreover, the possible toxicological concern from some potentially toxic elements (PTEs), namely Cd, Cu, Fe, Pb, and Zn, which may be abundant in WD was verified. After four weeks, we found that 0.25% WD not only increases lettuce biomass, which has an economic value, but also has beneficial effects on other qualitative parameters such as sugars and total sweetness. On the other hand, the use of 0.5% WD decreased the content of soluble sugars, suggesting a hormetic-type effect. We did not find evidence of further beneficial effects from the addition to WD of plant-derived corroborants, nor of any enrichment in the content of the investigated PTEs.

Effect of biochar and hydrochar from cow manure and reed straw on lettuce growth in an acidified soil

Soil acidification has become a major environmental and economic concern worldwide. Char materials (e.g biochar, hydrochar) have attracted considerable attention as soil amendments to restore degraded soil. However, the comparative study of biochar and hydrochar on plant growth in acidified soil is limited. In this study, a microcosmic experiment was used to compare the effect of biochar and hydrochar from cow manure (CBC, CHC) and reed straw (RBC, RHC) on the growth of lettuce in the acidified soil. CBC and RHC significantly increased and decreased the biomass of lettuce by 18.7% and 32.5% in the acidified soil, respectively. The increase of the lettuce growth by CBC primarily attributed to the enhancement of soil properties (SOM and pH) and soil nutrient content (Olsen-P, K, Ca, Mg, Zn, Fe and Mn). Moreover, CBC enhanced the microbial activity and complexity and increased the abundance of beneficial genera like Gemmatimonas, Ramlibacter and Haliangium, which improved soil health and might indirectly benefited the lettuce growth. Our findings highlighted the priority of char materials feedstock and preparation technology for remediating the acidified soil.

Loading ferric lignin on polyethylene film and its influence on arsenic-polluted soil and growth of romaine lettuce plant.

This work developed a composite (Pe-FeLs) which loaded ferric lignin on polyethylene film (PE film) by chemical modification and physico-chemically characterized by Microscope, FESEM with elemental mapping analysis, and XRD. Microscope pictures showed that chemical modification did not destroy the appearance of PE film. The FESEM images of Pe-FeLs showed the well-distributed clusters could be clearly seen and most of the particles were spherical morphology. Elemental mapping of individual element on Pe-FeLs clearly indicated the existing of iron. The XRD pattern showed the amorphous hydroxides of iron on Pe-FeLs. In arsenic solution, the total arsenic adsorption capacity of Pe-FeLs was much higher than that of ferric lignin and PE, which showed Pe-FeLs had the ability to adsorb arsenic. For making Pe-FeLs work well in the soil, a Pe-FeLs system was set up with plastic grid plate, PE film with holes, Pe-FeLs, PE film, and plastic grid plate from the upper to bottom in order. With applying Pe-FeLs system under the soil, arsenic was significantly reduced by 25.5 ~ 53.4% in heavily, moderately, and lower arsenic-polluted soils, the biomass of the romaine lettuce increased and arsenic accumulation in the romaine lettuce decreased.

Morphological and Physiological Screening to Predict Lettuce Biomass Production in Controlled Environment Agriculture

Fast growth and rapid turnover is an important crop trait in controlled environment agriculture (CEA) due to its high cost. An ideal screening approach for fast-growing cultivars should detect desirable phenotypes non-invasively at an early growth stage, based on morphological and/or physiological traits. Hence, we established a rapid screening protocol based on a simple chlorophyll fluorescence imaging (CFI) technique to quantify the projected canopy size (PCS) of plants, combined with electron transport rate (ETR) measurements using a chlorophyll fluorometer. Eleven lettuce cultivars (Lactuca sativa), selected based on morphological differences, were grown in a greenhouse and imaged twice a week. Shoot dry weight (DW) of green cultivars at harvest 51 days after germination (DAG) was correlated with PCS at 13 DAG (R2 = 0.74), when the first true leaves had just appeared and the PCS was <8.5 cm2. However, early PCS of high anthocyanin (red) cultivars was not predictive of DW. Because light absorption by anthocyanins reduces the amount of photons available for photosynthesis, anthocyanins lower light use efficiency (LUE; DW/total incident light on canopy over the cropping cycle) and reduce growth. Additionally, the total incident light on the canopy throughout the cropping cycle explained 90% and 55% of variability in DW within green and red cultivars, respectively. Estimated leaf level ETR at a photosynthetic photon flux density (PPFD) of 200 or 1000 µmol m−2 s−1 were not correlated with DW in either green or red cultivars. In conclusion, early PCS quantification is a useful tool for the selection of fast-growing green lettuce phenotypes. However, this approach may not work in cultivars with high anthocyanin content because anthocyanins direct excitation energy away from photosynthesis and growth, weakening the correlation between incident light and growth.

Viabilidade agroeconômica do consórcio alface-beterraba sob adubação verde no semiárido

ABSTRACT Producers who practice intercropped systems of leafy vegetables with tuberous ones, generally seek for systems that provide high productivity, greater diversification of production, high quality products and mainly agroeconomic return. Therefore, the objective of this work was to assess whether there is agro-economic viability of lettuce bi-cropping in intercrop with beet, under different equitable amounts of Merremia aegyptia and Calotropis procera biomass (20, 35, 50 and 65 t ha-1 on dry basis) and population densities of lettuce (150, 200, 250 and 300 thousand plants of lettuce ha-1), combined with 500 thousand plants per hectare of beet in two years of cultivation in semi-arid environment. Productivity of lettuce leaves and commercial productivity of beet roots were evaluated, as well as the agronomic indices: land equivalent ratio (LER), area-time equivalent ratio (ATER), productive efficiency index (PEI), score of the canonical variable (Z), actual yield loss (AYL), and the economic indicators: gross income (GI), net income (NI), monetary advantage (MA) and rate of return (RR). The highest agro-economic returns of the lettuce-beet intercropping were achieved with LER and ATER of 2.59 and 1.39; PEI and Z of 0.97 and 2.32; and AYL of 10.66; and GI, NI and MA of 94,742.89; 59,121.45; 56,631.98 R$ ha-1 and RR of R$ 2.75 for each real invested, respectively, in the combination of 65 t ha-1 of M. aegyptia and C. procera biomass and lettuce population density 300 thousand plants per hectare. Beet was the dominant crop and lettuce the dominated one. The lettuce and beet intercropping is highly viable when properly manured with biomass of M. aegyptia and C. procera, as they express agronomic and economic viability and sustainability in semi-arid environment.

Selenium treated foliage and biochar treated soil for improved lettuce (Lactuca sativa L.) growth in Cd-polluted soil

Cadmium (Cd) pollution in farmland soils is a serious concern due to its devastating effects on living organisms. This requires developing effective strategies to inhibit the Cd absorption and accumulation by vegetables. In this study, the influence of soil applied biochar (BC) (10 and 30 g kg−1) and foliage applied selenium (Se) fertilizer (1 and 3 mg L−1) on the absorption and accumulation of Cd and growth of lettuce under Cd stress (1 and 3 mg/kg) was evaluated. In Cd-contaminated soil, the application of BC and Se significantly increased lettuce biomass and chlorophyll contents by 74% and 100%, respectively, compared to control in lettuce. The combined application of BC and Se at (B 30 g kg−1, Se 3 mg L−1) was effective in reducing the accumulation of Cd by lettuce shoot by 73.41% than control. Co-application of BC and Se enhanced the activities of antioxidant enzymes catalase, superoxide dismutase by 77 and 96%, respectively, and reduced the malondialdehyde contents by 56% than control. Application of biochar (30 g kg−1) significantly increased the soil electrical conductivity and soil organic carbon of soil by 48 and 41%, respectively as compared to control. The combination of BC and Se (B 30 g kg−1, Se 3 mg L−1) reduced the Cd contents in lettuce shoots from 0.79 mg kg−1 to 0.08 mg kg−1 below the national food safety standard threshold (0.2 mg kg−1 Cd). Overall, this study revealed that the integrated application of BC (30 g kg−1) and Se (3 mg L−1) can help prevent the absorption of Cd by lettuce. However, the effectiveness of BC in remediating trace metals may decrease with time due to the aging factor and leaching alkalinity of BC, so long-term field experiments are needed to enhance the understanding of BC efficiency and an appropriate Se concentration for specific green soil remediation goals.

Growth and yield of tilapia hybrid (red tilapia) in aquaponics system

An aquaponics system was studied through the integrated culture of tilapia hybrid (Red Tilapia) and lettuce var. Estrosa in a recirculating system for 100 days. Red Tilapia with an Average Body Weight (ABW) of 36.99g were stocked in two treatments, 80 fish/m3 (Treatment I) and 100 fish/m3 (Treatment II), to assess the fish growth, survival, yield and production of lettuce. Specific Growth Rate (SGR) in Treatment I was 1.03 and Treatment II, 1.14. Feed Conversion Ratio (FCR) varies from 1.83 to 1.90, associated with stocking density. Treatment II incurred the highest survival rate of 92.85% while Treatment I has 90.19%. Biomass production of red tilapia was significantly higher in Treatment I with 1,761.00 g than in Treatment II with 1,341.00 g (p = 0.012). Highest yield of lettuce was obtained during the second cropping with 250.00g for Treatment I and 202.00g for Treatment II, but no significant difference was observed between the two treatments. Correlation analysis showed no significant relationship between red tilapia weights and water quality parameters such as ammonia, nitrite, nitrate, temperature, pH, Total Dissolved Solids, and DO. However, a significant positive relationship was revealed between the biomass of lettuce and nitrite during the first cropping in Treatment II. This study demonstrated the stocking density of 80 fish/m3 had better effect on the growth, FCR, and biomass production of red tilapia under an aquaponics system.

Impact of biosolarization with almond hull and shell amendments for the control of Fusarium oxysporum f. sp. lactucae in a lettuce/tomato cropping system

Biosolarization is an alternative to chemical fumigation that couples solarization and organic amendments to control diseases by increasing temperature and microbial activity. A field study was conducted to evaluate the efficacy of biosolarization, using almond processing residues from two varieties, to control propagules of Fusarium oxysporum f. sp. lactucae, the causal agent of Fusarium wilt of lettuce. Peak soil temperatures of solarized and biosolarized soils were 6–15 °C higher than control soils, and biosolarized soils experienced 1 to 3 °C higher temperatures on average and 10 to 27°C-day higher cumulative temperatures than soil solarized without amendment. Residues were high in endogenous organic acids, between 144 and 298 mM combined acetic, lactic, succinic, and butyric acids. After eight days of treatment, solarized soils only reduced the population of Fusarium oxysporum f. sp. lactucae by 9% compared to the average non-treated non-amended control plots; whereas soils solarized and amended with residues from pollinator varieties of almonds showed a greater pathogen reduction of 63%. In this instance, Fusarium wilt had no effect on plant health due to low pressure and moderate innate plant resistance. Soils amended with nonpareil residues had similar lettuce biomass and health scores to untreated plots, but lower health scores than the solarized treatments. This may be due to residual organic acids detected in biosolarized plots 3–4 weeks after treatments (1–57 mM), which significantly correlated to poor lettuce health score. Roughly, one year after soil treatment, solarized plots continued to out-perform pollinator-residue amended plots. Germination assays indicate biosolarization outcomes may be improved with increased aerobic remediation time.

Effect of Commercial Amendments on Immobilization of Arsenic, Copper, and Zinc in Contaminated Soil: Comprehensive Assessing to Plant Uptake Combined with a Microbial Community Approach

Identifying the proper chemical and biological materials as soil amendments is a great concern because they replace soil properties and subsequently change the soil quality. Hence, this study was conducted to evaluate the effects of a diverse range of soil amendments including bentonite (B), talc (T), activated carbon (AC), and cornstarch (CS) in form of sole and composite on the immobilization and bioavailability of As, Cu, and Zn. The amendments were characterized by SEM, FT-IR, and XRF, and applied at 2% (w/w) in the experimental pots with an Asteraceae (i.e., lettuce) for 45 days to monitor plant growth parameters and soil microbial community. Soil pH from 6.1 ± 0.02 significantly increased in the amended soils with the maximum value found for TAC (7.4 ± 0.04). The results showed that soil amendments reduced easily in an exchangeable fractionation of As, Cu, and Zn with the maximum values found for BAC by 66.4%, AC by 84.2%, and T by 89.7% respectively. Adding B, T, AC, and their composites induced dry biomass of lettuce >40 wt.%, while CS and its composites did not affect the dry biomass of the plant. The average content of Cu and Zn in plant tissues decreased >45 wt.% in B, AC, and their composites amended soils; meanwhile, AC and its composites mitigated As uptake by >30 wt.% in lettuce. The results of Biolog Ecoplate showed that the amending soils improved the microbial community, especially for composites (e.g., TCS). The results demonstrated that adding composites amendments provided an efficient method for the immobilization of metals and metalloids, and also induced plant growth parameters and microbial community.

Toxic effects of polystyrene and dibutyl phthalate on purple lettuce

As a carrier of environmental pollutants, microplastics have received wide concerns in recent years. However, the direct and indirect effects of the coexistence of polystyrene particles (PS) and pollutants on vegetables are still unclear. Here, the combined effects of 0.25, 0.50, 1.0 mg·mL-1 PS and 5 mg·L-1 dibutyl phthalate (DBP) on the biomass and biochemical indices of purple lettuce were investigated in hydroponic experiments. The results showed that the presence of PS increased the inhibition of DBP on lettuce biomass and increased O2-· content in roots and leaves relative to the control group with DBP alone, with positive consequences on the activities of supero-xide dismutase, ascorbic acid peroxidase, dehydroascorbate reductase and monodehydroascorbate reductase. According to transmission electron microscope analysis, plasmolysis occurred in root cells under the treatment of DBP alone, cell wall was damaged in PS-only treatment, and the negative effect was enhanced when DBP and PS coexisted. Therefore, the combined pollution of PS and DBP aggravated the toxic effect on purple lettuce.

Foliar application of gibberellin inhibits the cadmium uptake and xylem transport in lettuce (Lactuca sativa L.)

Gibberellin (GA) has been shown to exert numerous beneficial physiological functions in the resistance of plant to various abiotic stresses, however, the mechanism of GA for the mitigation of Cd stress in vegetables has not been well established. This study was carried out to investigate the effect of GA on the growth and Cd uptake in lettuce plants. Result showed that 10 µmol/L GA treatment restored part of the root morphology and vigor of lettuce under Cd stress by increasing the total root length, surface area and total root tip number, which directly showed an increased biomass of lettuce. On the other hand, GA reduced Cd uptake by roots and Cd root-to-shoot translocation by down-regulated expression of IRT1, Nramp1, HMA2 and HMA4, which finally alleviated the toxic effects of Cd on lettuce leaves, as confirmed by Non-invasive micro-test Technique (NMT) results. Overall, these findings provide new insights into the mechanism of cadmium toxicity mitigation in vegetables by GA and provide a theoretical basis for the development of physiological blockers with gibberellin components.

Comparison of growth characteristics, functional qualities, and texture of hydroponically grown and soil-grown lettuce

Hydroponics has become one of the most popular approaches in today's agricultural production. Yet it is questionable whether hydroponics produce vegetables with comparable quality to soil-grown vegetables. In this study, hydroponically and soil-grown lettuce were compared for morphology, texture, antioxidant capacity, and functional quality. Giant Caesar lettuce was grown in laboratory-constructed hydroponic or soil systems for 35 days. Above-ground plant size, biomass, and leaf size of hydroponic lettuce were not significantly different from soil-grown lettuce. Hydroponic lettuce had significantly (p < 0.05) longer roots, higher moisture and lower ash. No significant difference in ascorbic acid, chlorophyll, β-carotenes, and total phenolics was found in freeze-dried lettuce. However, all compounds analyzed were significantly higher in soil-grown lettuce based on fresh weight. Antioxidant capacity of soil-grown lettuce was significantly higher on both dry- (15.32%) and wet-basis (41.20%). Hydroponic lettuce had softer leaves and firmer midribs; potentially linked to increased lignin (24.18%) in plant cell walls. This represents the first comprehensive side-by-side growth study demonstrating that lettuce grown hydroponically is not the same quality as that grown in soil.

Assessment of phytotoxicity and impact on the enzymatic activity of soil microorganisms caused by veterinary antibiotics used in Brazilian farms

This work aimed to evaluate the impact of veterinary antibiotics on biomass phytoproductivity and soil enzyme activity. The soil was sampled in the city of Camboriú (state of SC, Brazil). The soil enzyme activity was assessed through hydrolysis of fluorescein diacetate (FDA), while phytotoxicity was tested using Lactuca sativa (lettuce). Results showed that the most appropriate exposure time to assess the impact of antibiotics on soil microbiology was 24 h, while the incubation time of 3 h was the most appropriate for FDA hydrolysis. Ampicillin and Amoxicillin at the tested concentrations did not interfere with the enzyme activity of the soil microbiota, while Oxytetracycline and Neomycin showed a significant reduction in soil enzyme activity. For the dry and wet biomass of lettuce, 2% Colistin and 1% Ampicillin were the treatments that reduced lettuce biomass. Hence, the use of excessive antibiotics in animal production may lead to environmental impacts and, in the future, to public health problems.

Dose-Dependent Effect of ZnO Quantum Dots for Lettuce Growth.

As the cadmium-free semiconductor quantum dots, ZnO quantum dots (ZnO QDs) have wide potential applications in agriculture. However, the effects of ZnO quantum dots on crop growth and nutritional quality have not been fully studied. In this work, the lettuce was sprayed with different concentrations of ZnO QDs from 50 to 500 mg·L–1 to evaluate their influence on lettuce antioxidant, biomass, and nutritional quality. The results showed that ZnO QDs existed in the lettuce in the form of Zn2+. Lettuce treated with 500 mg·L–1 ZnO QDs would produce a large amount of reactive oxygen species (ROS), which adversely affected the absorption of nutrients, soluble protein content, and chlorophyll content, thus reducing plant biomass. When the concentrations range from 50 to 200 mg·L–1, the antioxidant enzyme systems of lettuce were triggered to counteract the damage caused by excessive ROS. Moreover, ZnO QDs at this level promoted Ca, Mg, Fe, Mn, Zn, and B absorption and accumulation; increased soluble sugar content; and improved the lettuce biomass and nutritional quality.

Foliar-applied polystyrene nanoplastics (PSNPs) reduce the growth and nutritional quality of lettuce (Lactuca sativa L.).

Currently, there is a lack of information about the influence of foliar-applied nanoplastics on crop growth and nutritional quality. To fill the knowledge gap, soil-grown lettuces (Lactuca sativa L.) were foliar-exposed to polystyrene nanoplastics (PSNPs) at 0, 0.1 and 1mg/L for one month. Foliar exposure to PSNPs significantly decreased the dry weight, height, and leaf area of lettuce by 14.3%-27.3%, 24.2%-27.3%, and 12.7%-19.2%, respectively, compared with the control. Similarly, plant pigment content (chlorophyll a, b and carotenoid) was considerably reduced (9.1%, 8.7%, 12.5%) at 1mg/L PSNPs. However, the significant increase in electrolyte leakage rate (18.6%-25.5%) and the decrease in total antioxidant capacity (12.4%-26%) were the key indicators of oxidative stress in lettuce leaves, demonstrating the phytotoxicity of PSNPs by foliar exposure. In addition, the remarkable reduction in micronutrients and essential amino acids demonstrated a decrease in nutritional quality of lettuce caused by PSNPs. Besides, SEM and TEM analysis indicated the possible absorption of PSNPs through leaves stoma and the translocation downwards to plant roots. This study provides new information about the interaction of airborne NPs with plants. It also warns against atmospheric NPs pollution that the adverse effects of airborne NPs on crop production and food quality should be assessed as a matter of urgency.

Biological Effect of Tetracycline Antibiotics on a Soil-Lettuce System and Its Migration Degradation Characteristics

Residual tetracycline antibiotics (TCs) in farmland soils with the application of livestock manure cause risks to the growth of vegetables and soil ecology. Here, pot experiments are carried out using through exogenous addition of different levels of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC), to study the physiological toxicity, uptake, and transportation of TCs in lettuce. The subsequent degradation of TCs in soil was also evaluated along with analyses of soil enzyme activity and microbial population dynamics. The results showed that the biomass of lettuce decreased with application of TCs as well as the chlorophyll-a, chlorophyll-b, and carotenoid content. Consequently, net photosynthetic rates were inhibited, and SOD, POD, and CAT increased under the stress imposed by the TCs. With an increase in the level of TC application, uptake by lettuce plants increased while the bioconcentration and translocation factors decreased. When OTC, TC, and CTC in the soil were below 150 mg·kg-1, the health risk from the edible parts of lettuce was low (HQ<0.1). The TC degradation rate in different soils was ranked in the order of control soil > rhizosphere soil > bulk soil. The OTC degradation rates in the soils were significantly lower than for TC and CTC. TCs (150-1350 mg·kg-1) significantly inhibited urease and rhizosphere catalase activity in soil and reduced the number of soil culturable bacteria and fungi.

Comparative analysis of fresh and dry free-floating aquatic plant Pistia stratiotes via chemical pretreatment for second-generation (2G) bioethanol production

In the effort to manage global warming and fossil carbon emissions, many countries are suggesting brand-new policies to make their energy matrix much more renewable. The boost share of bioethanol as a transportation fuel becomes a short-term option since its production technology is fully grown and combined with gasoline. The 2nd generation ethanol still has involvement on the planet biofuels circumstance. In this study, water lettuce (Pistia stratiotes) fresh and dry biomass applied with alkalis (NaOH) and acid (H2SO4) were combined to pretreat the abundant free-floating aquatic plant water lettuce biomass. Naturally, the water lettuce accumulates food in the form of starch, suitable for bioethanol production. The results showed that the highest total sugar (11.350 ± 0.09%), reducing sugar (4.773 ± 0.15%), and ethanol (15. 385 g/L) were obtained after pretreatment of dried water lettuce with cellulase. Consequently, water lettuce was high feasible for sustainable bioethanol production.

Dynamic Responses of Ascorbate Pool and Metabolism in Lettuce to Light Intensity at Night Time under Continuous Light Provided by Red and Blue LEDs.

To understand the dynamic changes of hydroponic lettuce growth, ascorbate (AsA) pool and metabolism under two different dark period light intensities (LL, 20 μmol·m−2·s−1; CL, 200 μmol·m−2·s−1) of continuous light and normal light (NL, 0 μmol·m−2·s−1) provided by red (R) and blue (B) LEDs, the chlorophyll fluorescence parameters, ascorbate pool size, AsA metabolism-related enzyme activities, and H2O2 contents of lettuce were measured at 0, 8, 16, 24, 32, 40, 48, 56, 64, and 72 h after light treatment and the lettuce growth parameters were measured on the 9th day after light treatment. The results showed that compared with the NL, CL treatment for 9 days significantly increased the biomass, dry matter content, and specific leaf weight of lettuce, but had no significant effect on the leaf area and root-to-shoot ratio; LL had no significant effect on lettuce biomass, but it would reduce the root-shoot ratio. Compared with the NL, the AsA content of CL increased significantly within 8 h after light treatment (at the end of first dark period), and then maintained at a relatively stable level with a slight increase; there was no significant difference in AsA contents between NL and LL showing the same circadian rhythm characteristics. Overall, the activities of L-galactono-1,4-lactone dehydrogenase (GalLDH), ascorbate peroxidase(APX), monodehydroascorbate reductase (MDHAR), and glutathione reductase (GR) under CL were the highest among the three treatments, and the differences with the other two treatments reached significant levels at several time points; there was almost no significant difference in the activities of GalLDH, APX, MDHAR, and GR between NL and LL; there was no significant difference in the activities of dehydroascorbate reductase (DHAR) under different treatments. Compared with the NL, CL caused a sharp decrease of PSⅡ maximal photochemical efficiency (Fv/Fm) in lettuce within 0–8 h after treatment, which then stabilized at a relatively stable level; the Fv/Fm value under the LL was almost the same as the NL. Except for 32 h, the H2O2 content of lettuce under CL was the highest among the three treatments during the entire experimental period, and was significantly higher than that of NL at several time points; the H2O2 content of LL was almost the same as NL. In summary, lettuce biomass, AsA contents, AsA metabolism-related enzyme activities, chlorophyll fluorescence parameters, and H2O2 contents were regulated by the dark period light intensities of continuous light rather than continuous light signals.

A type dependent effect of treated wastewater matrix on seed germination and food production

Municipal wastewater treated by membrane bioreactor, either aerobically (AeMBR) or anaerobically (AnMBR), can be reused to irrigate crops. However, post-AeMBR and post-AnMBR effluent have different water quality that may impact crop growth and yield. This study aims to assess for differences in water quality from both AeMBR and AnMBR, and determine if the type of treated wastewater matrix would impact seed germination and crop yield. Compared to post-AeMBR and control, post-AnMBR effluent had a negative impact on seed germination for both tomatoes and lettuces. The use of post-AnMBR but not post-AeMBR effluent also resulted in a higher number of unripe tomato fruits at the time of harvesting. However, when post-AnMBR effluent was diluted to 25% and 75% v/v with tap water, higher lettuce biomass was harvested compared to the same concentrations of post-AeMBR effluent and control. The observed differences in germination and yield were likely due to differences in the concentrations of heavy metals (e.g. Zn) and steroids or phytohormones (e.g. testosterone, gibberellic acid) present in both post-MBR effluents. This study demonstrated that the type of treated wastewater generated from different upstream treatment technologies can potentially impact crop yield based on the crop type. By understanding how the type of treated wastewater affect downstream agricultural activities, changes in management practices can be made accordingly.

Effects of Microbes from Coal-Related Commercial Humic Substances on Hydroponic Crop Cultivation: A Microbiological View for Agronomical Use of Humic Substances.

Here, coal-related humic substances (HSs) were examined to confirm whether sterilization treatments induce their inferior ability to stimulate lettuce in hydroponic cultivations. Interestingly, a drastic reduction in both lettuce biomass and microbial colony-forming units of the crop culture solutions was observed when the autoclaved HSs were treated. Some microbial genera (i.e., Bacillus and Aspergillus) identifiable in the bare HS-treated hydroponic systems were able to be isolated by direct inoculation of bare HS powders on conventional microbial nutrients, supporting that flourishing microbes in the hydroponic cultivations derive from bare HSs-treated. Moreover, coincubation of some isolated bacterial and fungal strains (i.e., Bacillus and Aspergillus genera) from HSs with lettuce resulted in a significant increase in plant biomass and enhanced resistance to NaCl-related abiotic stresses. Microbial volatile organic compounds renowned for plant stimulation were detected by using solid-phase microextraction coupled with gas chromatography-mass spectrometry. It was finally confirmed that the isolates are capable of utilizing carbon substrates such as pectin and tween 20 or 40, which are relevant to those of microbes isolated from peat and leonardite (i.e., HS extraction sources). Overall, our results suggest that microbiological factors could be considered when commercial coal-related HSs are applied in hydroponic crop cultivations.