In this study, antioxidant processes were searched for in macrophyte duckweed to investigate tolerance mechanisms in this species against oxidative damage caused by salinity stress. Biochemical and ...histological analyses were performed on four
Lemna aequinoctialis
clones grown in Schenk-Hildebrandt medium, 0.5 × SH, supplemented with 1% sucrose liquid medium containing or not containing NaCl in different NaCl concentrations (0, 25 and 50 mM). For most clones, the salt stress effects caused growth inhibition and antioxidant responses at 50 mM NaCl. Also, starch and reducing sugar accumulations were increased with salt, whereas the photosynthetic pigment content was reduced in clone
L. aequinoctialis
5569. The plant growth inhibition reflects the oxidative stress shown by the significant increase in malondialdehyde (MDA) and hydrogen peroxide (H
2
O
2
) content. In the
L. aequinoctialis
5568 clone, with the highest MDA levels, no antioxidant enzymatic activity was observed. The
L. aequinoctialis
5570 clone presented higher ascorbate peroxidase and catalase activities in parallel, indicating that the efficiency of the defence mechanism relies on synchrony between such enzyme activities toward successive elimination of reactive oxygen species and resulting in the assurance of some level of protection of the metabolism from oxidative damage. Considering the moderate salt stress (25 mM), the maintenance of MDA content and small growth inhibition associated with the high starch production suggested the acclimation efficiency of
L. aequinoctialis
5570 and 5567 clones, indicating that they may be suitable for cultivation under moderate saline conditions, serving as biofuel feedstock. In addition, this study demonstrates great intraspecific phenotypic plasticity of duckweed,
L. aequinoctialis
, from closely related clones.
An experiment on the use of duckweed powder as a fish feed on monoculture of silver carp (Hypophthalmichthys molitrix) was conducted in 6 ponds for a period of 75 days. The area of the each pond was ...one decimal. The experiment was carried out under two treatments, each with 3 replications. A combination of duckweed powder and rice bran at the ratio of 3:1 was supplied at the rate of 4% of total body weight in the ponds under treatment-I. On the other hand, the ponds under treatment-II were without supplying of feed. Each of the ponds under both treatments were stocked with 45 fingerlings of silver carp (H. molitrix). The average initial length and weight of the fingerlings were 14.60 cm and 33.48 g, respectively. The ponds were fertilized fortnightly with poultry droppings at the rate of 2 kg, urea 60 g and TSP 90 g decimal-1. During the experimental period the ranges of physico-chemical parameters viz. water depth (0.82 to 0.90 m), water temperature (17.80 to 26.7 °C), air temperature (19.11 to 28.29 °C), transparency (28.00 to 34.00 cm), dissolved oxygen (6.70 to 8.20 mg L-1), pH (6.70 to 8.00), total alkalinity (170 to 210 mg L-1), free CO2 (0.0 to 3.50 mg L-1), phosphate-phosphorus (1.2 to 2.9 mg L-1), and nitrate-nitrogen (3.1 to 4.5 mg L-1) were within the productive limit and more or less similar in all the ponds under treatments I and II. There were 25 genera of phytoplankton under four major groups and 10 genera of zooplankton under three major groups in the experimental ponds. Mean survival rates under treatment-I and treatment-II were 97.78% and 95.56%, respectively. The specific growth rates (SGR % per day) of the fish found under treatment-I and treatment-II were 0.98% and 0.49%. The calculated net production of the ponds under treatment-I was 1.87 ton ha-1 yr-1 and that of the ponds under treatment-II, was 0.74 ton ha-1 yr-1. By 't' test, it was found that the net fish production of treatment-I was significantly (p<0.01) higher than that of treatment-II, and cost return relationship was found that the net profit of treatment-I and treatment-II were more or less similar. Finally, it can be concluded that duckweed powder as an ingredient of fish feed had significant impacts on production of silver carp, which do not consume duckweed as fresh and raw condition. Thus, duckweed powder can be used as feed for most fishes.
Int. J. Agril. Res. Innov. & Tech. 9 (1): 73-83, June, 2019
Glycosyltransferases (GTs) are carbohydrate-active enzymes that are encoded by the genomes of organisms spanning all domains of life. GTs catalyze glycosidic bond formation, transferring a sugar ...monomer from an activated donor to an acceptor substrate, often another saccharide. GTs from family 47 (GT47, PF03016) are involved in the synthesis of complex glycoproteins in mammals and insects and play a major role in the synthesis of almost every class of polysaccharide in plants, with the exception of cellulose, callose, and mixed linkage β-1,3/1,4-glucan. GT47 enzymes adopt a GT-B fold and catalyze the formation of glycosidic bonds through an inverting mechanism. Unlike animal genomes, which encode few GT47 enzymes, plant genomes contain 30 or more diverse GT47 coding sequences. Our current knowledge of the GT47 family across plant species brings us an interesting view, showcasing how members exhibit a great diversity in both donor and acceptor substrate specificity, even for members that are classified in the same phylogenetic clade. Thus, we discuss how plant GT47 family members represent a great case to study the relationship between substrate specificity, protein structure, and protein evolution. Most of the plant GT47 enzymes that are identified to date are involved in biosynthesis of plant cell wall polysaccharides, including xyloglucan, xylan, mannan, and pectins. This indicates unique and crucial roles of plant GT47 enzymes in cell wall formation. The aim of this review is to summarize findings about GT47 enzymes and highlight new challenges and approaches on the horizon to study this family.
The main topic of this study is the bioremediation potential of the common duckweed,
L., and selected rhizospheric bacterial strains in removing phenol from aqueous environments at extremely high ...initial phenol concentrations. To that end, fluorescence microscopy, MIC tests, biofilm formation, the phenol removal test (4-AAP method), the Salkowski essay, and studies of multiplication rates of sterile and inoculated duckweed in MS medium with phenol (200, 500, 750, and 1000 mg L
) were conducted. Out of seven bacterial strains, six were identified as epiphytes or endophytes that efficiently removed phenol. The phenol removal experiment showed that the bacteria/duckweed system was more efficient during the first 24 h compared to the sterile duckweed control group. At the end of this experiment, almost 90% of the initial phenol concentration was removed by both groups, respectively. The bacteria stimulated the duckweed multiplication even at a high bacterial population density (>10
CFU mL
) over a prolonged period of time (14 days). All bacterial strains were sensitive to all the applied antibiotics and formed biofilms in vitro. The dual bacteria/duckweed system, especially the one containing strain 43-
C32-106/3, Accession No. MF526939, had a number of characteristics that are advantageous in bioremediation, such as high phenol removal efficiency, biofilm formation, safety (antibiotic sensitivity), and stimulation of duckweed multiplication.
Main conclusion
UVB radiation caused irradiance-dependent and target-specific responses in non-UVB acclimated
Lemna minor
. Conceptual toxicity pathways were developed to propose causal relationships ...between UVB-mediated effects at multiple levels of biological organisation.
Macrophytes inhabit waterways around the world and are used in hydroponics or aquaponics for different purposes such as feed and wastewater treatment and are thus exposed to elevated levels of UVB from natural and artificial sources. Although high UVB levels are harmful to macrophytes, mechanistic understanding of irradiance-dependent effects and associated modes of action in non-UVB acclimated plants still remains low. The present study was conducted to characterise the irradiance-dependent mechanisms of UVB leading to growth inhibition in
Lemna minor
as an aquatic macrophyte model. The
L. minor
were continuously exposed to UVB (0.008–4.2 W m
−2
) and constant UVA (4 W m
−2
) and photosynthetically active radiation, PAR (80 µmol m
−2
s
−1
) for 7 days. A suite of bioassays was deployed to assess effects on oxidative stress, photosynthesis, DNA damage, and transcription of antioxidant biosynthesis, DNA repair, programmed cell death, pigment metabolism and respiration. The results showed that UVB triggered both irradiance-dependent and target-specific effects at multiple levels of biological organization, whereas exposure to UVA alone did not cause any effects. Inhibition of photosystem II and induction of carotenoids were observed at 0.23 W m
−2
, whereas growth inhibition, excessive reactive oxygen species, lipid peroxidation, cyclobutane pyrimidine dimer formation, mitochondrial membrane potential reduction and chlorophyll depletion were observed at 0.5–1 W m
−2
. Relationships between responses at different levels of biological organization were used to establish a putative network of toxicity pathways to improve our understanding of UVB effects in aquatic macrophytes under continuous UVB exposures. Additional studies under natural illuminations were proposed to assess whether these putative toxicity pathways may also be relevant for more ecologically relevant exposure scenarios.
For evaluating duckweed biomass as a bioresource, the specific growth rate and the chemical constituents of duckweed of four kinds were investigated. Spirodela polyrrhiza, Lemna minor, Wolffia ...arrhiza, and Wolffia globosa commonly showed high specific growth rates of 0.22–0.30 d−1 with initial concentrations of nitrogen >3.0 kg m−3 and phosphorus >5.0 kg m−3. All duckweeds had high sugar contents greater than 300 g kg−1 of dry mass. Especially, vegetative fronds of W. globosa showed the highest sugar content of 410 g kg−1 of dry mass. The duckweed biomass was pretreated easily by heating at 121 °C for saccharification using α-amylase and amyloglucosidase. The ethanol yield of W. globosa biomass in the simultaneous saccharification and fermentation (SSF) using the enzymes and dry yeast was 170 g kg−1 of dry mass, whereas the succinate yield in the SSF using the enzymes and Actinobacillus succinogenes was 200 g kg−1 of dry mass. The production rates of ethanol and succinate from the W. globosa biomass were estimated as 0.58 kg m−2 y−1 and 0.68 kg m−2 y−1, respectively. The biomass of duckweed, with its high growth rate and high starch content, can be an excellent renewable feedstock for the production of ethanol and succinate as building block chemicals for the replacement of petrochemicals.
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•Duckweed of four kinds showed high specific growth rates of >0.22 d−1.•All duckweed had high sugar contents of >300 g kg−1.•Wolffia globosa showed the highest sugar content of 410 g kg−1.•The ethanol yield of the W. globosa biomass was 170 g kg−1.•The succinate yield of the W. globosa biomass was 200 g kg−1.
We created a combined system using duckweed and bacteria to enhance the efficiency of ammonium nitrogen (NH4+-N) and total nitrogen (TN) removal from aquaculture wastewater. Heterotrophic nitrifying ...bacterium was isolated from a sediment sample at an intensive land-based aquaculture farm. It was identified as Acinetobacter sp. strain A6 based on 16S rRNA gene sequence (accession number MF767879). The NH4+-N removal efficiency of the strain and duckweed in culture media and sampled aquaculture wastewater at 15°C was over 99% without any accumulation of nitrite or nitrate. This was significantly higher than strain A6 or duckweed alone. Interestingly, the presence of NO3- increased NH4+-N removal rate by 35.17%. Strain A6 and duckweed had mutual growth promoting-effects despite the presence of heavy metals and antibiotics stresses. In addition, strain A6 colonized abundantly and possibly formed biofilms in the inner leaves of duckweed, and possessed indoleacetic acid (IAA)- and siderophore-producing characteristics. The mutual growth promotion between strain A6 and duckweed may be the reason for their synergistic action of N removal.
Abstract
Background
A bioassay with severely mercury-stressed duckweed (
Lemna gibba
L.) had revealed growth-inhibiting effects of homeopathically potentised mercury(II) chloride (
Mercurius ...corrosivus, Merc-c.
). We hypothesised that effects of potentised preparations are dependent on the stress level of the organisms used in the bioassay. The aim of the present investigation was to examine the response of duckweed to potentised
Merc-c.
at a lower stress level.
Methods
Duckweed was moderately stressed with 2.5 mg/L mercury(II) chloride for 48 hours. Afterwards plants grew in either
Merc-c.
(seven different potency levels, 24x–30x) or water controls (unsuccussed or succussed water) for 7 days. Growth rates of the frond (leaf) area were determined using a computerised image-analysis system for day 0–3 and 3–7. Three independent experiments with potentised
Merc-c.
and three systematic negative control experiments were performed. All experiments were randomised and blinded.
Results
Unsuccussed and succussed water did not significantly differ in their effects on duckweed growth rate. The systematic negative control experiments did not yield any significant effects, thus providing evidence for the stability of the experimental system. Data from the two control groups and the seven treatment groups (
Merc-c.
24x–30x) were each pooled to increase statistical power. Duckweed growth rates for day 3–7 were enhanced (
p
< 0.05) after application of
Merc-c.
compared with the controls. Growth rates for day 0–3 were not influenced by the homeopathic preparations.
Conclusions
Moderately mercury-stressed
Lemna gibba
L. yielded evidence of growth-enhancing specific effects of
Merc-c.
24x–30x in the second observation period (day 3–7). This observation is complementary to previous experiments with severely mercury-stressed duckweed, in which a decrease in growth was observed in the first observation period (day 0–3). We hypothesise that the differing results are associated with the level of stress intensity (moderate vs. severe).
Between 62% and 92% of industrial and municipal wastewater in upper-middle, low-middle, and low income countries is discharged to the environment untreated, releasing valuable nutrients such as ...nitrogen (N) and phosphorus (P) into rivers, lakes, and oceans (Lipponen and Nikiforova, 2017). This, in addition to excess nutrients often present in agricultural runoff due to overuse and misuse of fertilizers, can lead to eutrophication, often causing irreparable damage to aquatic ecosystems. For these reasons, new techniques must be found to effectively recover waste nutrients and upcycle them into natural soil amendments that can be used to enrich soil quality and grow food for future generations while minimizing agricultural runoff. Duckweed is a small floating aquatic plant that can hyperaccumulate nutrients present in wastewater and agricultural runoff and then be harvested and reused to replace or supplement commercial soil fertilizers. As part of a two-year field trial, duckweed was tested for the second consecutive year in this study as a soil amendment in comparison to, and in combination with, commercial fertilizer for the growth of sorghum, a drought-resistant grain. Relative to fertilizer in all cases, soils amended with duckweed generated less ammonia and nitrate in surficial runoff. No differences in P in cumulative runoff were found among the different treatments (p = 0.509). Additionally, duckweed application produced sorghum grains with greater N and P content than other treatments (1.63 ± 0.03% N (p = 0.001) and 0.35 ± 0.0% P (p = 0.016)). Duckweed treatments also showed increased soil residue carbon and P after harvesting the crop. When normalized by germination rate, sorghum yield was similar across treatments. In agreement with first-year findings, the results indicated that duckweed may be a viable alternative to commercial fertilizer from an environmental and agricultural perspective, providing acceptable yields and contributing to the buildup of beneficial nutrients in the soil profile. Additional testing is needed to further evaluate potential germination inhibitors, greenhouse gas emissions (ex., N2O), and efficacy when applied to different crops and soil types.
•Nutrients in wastewater can be recovered by duckweed and reused in agriculture.•Duckweed amendments enrich soils by contributing beneficial nutrients.•Duckweed provides a slow release of nutrients over time for crop growth.•Soils amended with duckweed generate less ammonia and nitrate in surficial runoff.•Duckweed produces sorghum grains with greater N and P content than other treatments.
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