Hydroponic Solution Research Articles

Biochar Effects on Nutrients Retention and Release of Hydroponics Growth Media

Applying biochar (BC) to broad acre crops is an effective way to sequester carbon while improving soil fertility and reducing nutrient leaching. Adopting a similar approach in a hydroponic environment, BC may enhance nutrient availability and reduce natural fluctuations in the nutrient solution. This study monitored the effect of BC addition to peatmoss growth media with ratios of 0%, 5%, 25% and 50% on pH, electrical conductivity (EC) and macronutrient retention, over 15 days using hydroponic nutrient solution controls. Deionised water was used to measure nutrient releases in the closed loop hydroponic system, showing that biochar increased pH level in both retention and release stages. As expected, the pH increased by a maximum of 1.5 units with the highest biochar to growth media ratio due to the natural liming nature of the BC. The EC was also affected, as BC increased in the media EC reduced. With regards to retention of nutrients, BC recovered nitrate, phosphate, calcium and sulphate but did not affect magnesium. Potassium levels increased in solution with increasing BC ratio. In terms of outcomes relevant to global agriculture, the results show that the same level of production can nominally be obtained with around half the nutrient requirements.

Acquired salinity tolerance in rice: Plant growth dataset.

This article describes the growth of 18 acclimatized and 11 non-acclimatized rice varieties grown in a hydroponic nutrient solution in a glasshouse. Four plants from each variety were grown under control conditions, salinity stress following control conditions (salinity), and salinity stress following acclimation (salinity/acclimation) conditions. Sampling was performed at the end of the salinity treatment (36 days of growth). Growth traits such as shoot and root biomass accumulation and lengths were measured for each variety, and the average was calculated using four replicates. This dataset may aid interested researchers in making comparisons with their data and further advance the research on the salinity acclimation process in rice.

SALINITY TOLERANCE AND PHYTOREMEDIATION OF Na+ AND K+ IONS BY USING HALOPHYTES FROM CHOLISTAN RANGELAND, PAKISTAN

Salinity has been considered as the most important factor which adversely affects the plant growth and metabolism in arid and semi-arid areas. Salinity is increasing with times and is expected that 50% of arable land would be salinized till 2050. Present study investigated salinity tolerance and phytoremediation of Na+ and K+ by using halophytes; Cymbopogon jwarancusa, Aeluropus lagopoides, Panicum antidotale and Cenchrus setigerus. Plants were grown for 40 days in hydroponic solution for biomass productions, chlorophyll contents, membrane stability index (MSI) and phytoremediation. Completely Randomized Design (CRD) with four treatments and replications was used to check significance level at 5%. Fresh and dry biomass of each species was increased with increasing salinity level but decreased under highly saline conditions. P. antidotale contained highest fresh/dry weight (20.4 A) and (4.2A) at 140 mM NaCl treatment that decreased at 210 mM NaCl. A. lagopoides showed highest MSI at T3 (46.3 A) significance level that reduced at 210 mM NaCl (20.7 D). K+ concentrations in leaves/roots of all species reduced with elevated salinity (9327.4 A) was the highest K+ in leaves of A. lagopoides which reduced to (3976.2 D) at 210 mM NaCl. Na+ concentrations in the selected halophytes increased with the growing salt levels. Na+ concentration in leaves were (2331.8 D) and (3834.7 ppm) at 0 mM NaCl level while it was (9078 A) and (7494.3A) in P. antidotale and A. lagopoides at 210 mM NaCl respectively. Phytoremediation by halophytic grasses is time saving, economically viable and novel approach towards reclaiming saline soils.

Biofortification of calcium on mustard (Brassica juncea L.) and lettuce (Lactuca sativa) cultivated in floating hydroponic system

Calcium (Ca) is one of the essential macrominerals needed by the human body as a major component in the formation of bones and teeth. Calcium is fulfilled by eating calcium-rich foods, both animal and vegetable. Mustard and lettuce are vegetables that can be a source of Ca. Efforts to increase the Ca content in plants can be done through increasing the concentration of Ca given through fertilizer or in nutrient solution. However, excessive Ca application is not recommended because it will be toxic to plants. This study aims to determine the effect of various Ca concentrations in hydroponic nutrient solutions on the growth and yield of mustard vegetables (Brassica juncea L) and lettuce (Lactuca sativa L.). This study used a floating hydroponic system with a completely randomized design. Treatment of Ca concentrations of hydroponic nutrient solutions that were tried were 0, 100, 200, 300, and 400 ppm. The parameters observed were plant height, number of leaves, level of greenness of leaves, fresh and dry weight, and concentration of calcium in the leaves. The results showed that Ca treatment significantly affected the number of leaves and the level of leaf greenness. Application of 400 ppm Ca in hydroponic nutrient solution is the highest Ca concentration that could increase Ca content in mustard and lettuce plants. Application of Ca 300 ppm is the highest concentration of hydroponic nutrient solution that can increase the Ca content of plants without causing a decrease in plant biomass, and therefore the treatment of Ca 300 ppm can be used for biofortification of Ca by hydroponic in mustard and lettuce plants.

Uptake, phytovolatilization, and interconversion of 2,4-dibromophenol and 2,4-dibromoanisole in rice plants

The structural analogs, 2,4-dibromophenol (2,4-DBP) and 2,4-dibromoanisole (2,4-DBA), have both natural and artificial sources and are frequently detected in environmental matrices. Their environmental fates, especially volatilization, including both direct volatilization from cultivation solution and phytovolatilization through rice plants were evaluated using hydroponic exposure experiments. Results showed that 2,4-DBA displayed stronger volatilization tendency and more bioaccumulation in aboveground rice tissues. Total volatilized 2,4-DBA accounted for 4.74% of its initial mass and was 3.43 times greater than 2,4-DBP. Phytovolatilization of 2,4-DBA and 2,4-DBP contributed to 6.78% and 41.7% of their total volatilization, enhancing the emission of these two contaminants from hydroponic solution into atmosphere. In this study, the interconversion processes between 2,4-DBP and 2,4-DBA were first characterized in rice plants. The demethylation ratio of 2,4-DBA was 12.0%, 32.0 times higher than methylation of 2,4-DBP. Formation of corresponding metabolites through methylation and demethylation processes also contributed to the volatilization of 2,4-DBP and 2,4-DBA from hydroponic solution into the air phase. Methylation and demethylation processes increased phytovolatilization by 12.1% and 36.9% for 2,4-DBP and 2,4-DBA. Results indicate that phytovolatilization and interconversion processes in rice plants serve as important pathways for the global cycles of bromophenols and bromoanisoles.

Application of a Spectroscopic Analysis-Based Portable Sensor for Phosphate Quantitation in Hydroponic Solutions

Hydroponic plant culturing requires the concentration of nutrients in the supplied solution to be maintained at a constant level. For example, phosphate ion concentration directly affects crop growth, which necessitates the development of convenient and rapid techniques for on-site phosphate quantitation. Herein, we developed a new low-cost colorimetric method of quick on-site phosphate quantitation based on a modification of the conventional molybdenum colorimetric method. Specifically, the nutrient solution treated with ascorbic acid and molybdate was analyzed by colorimetric method after 10 min incubation, and a phosphate quantitation protocol was proposed. To verify this protocol, 50 nutrient solution samples with concentrations of 0–200 ppm were used to develop a model and perform a validation experiment, and the PLSR (Partial Least Squares Regression) and PCR (Principal Component Regression) models were developed and validated using a crossvalidation method and sample transmission spectra. The PLSR model, employing smoothing preprocessing at a 5 nm wavelength spacing, exhibited the best prediction performance and showed an error of ~10% within the measurement range during verification. In addition, an artificial neural network-based model achieved R2=0.93 for the training set and R2=0.86 for the validation set. Finally, we developed convenient-to-use software for phosphate ion quantitation by the presented method and performed a demonstration test.

Methyl Jasmonate Affects Photosynthesis Efficiency, Expression of HvTIP Genes and Nitrogen Homeostasis in Barley.

Jasmonates modulate many growth and developmental processes and act as stress hormones that play an important role in plant tolerance to biotic and abiotic stresses. Therefore, there is a need to identify the genes that are regulated through the jasmonate signalling pathway. Aquaporins, and among them the Tonoplast Intrinsic Proteins (TIPs), form the channels in cell membranes that are responsible for the precise regulation of the movement of water and other substrates between cell compartments. We identified the cis-regulatory motifs for the methyl jasmonate (MeJA)-induced genes in the promoter regions of all the HvTIP genes, which are active in barley seedlings, and thus we hypothesised that the HvTIP expression could be a response to jasmonate signalling. In the presented study, we determined the effect of methyl jasmonate on the growth parameters and photosynthesis efficiency of barley seedlings that had been exposed to different doses of MeJA (15–1000 µM × 120 h) in a hydroponic solution. All of the applied MeJA concentrations caused a significant reduction of barley seedling growth, which was most evident in the length of the first leaf sheath and dry leaf weight. The observed decrease of the PSII parameters after the exposure to high doses of MeJA (500 µM or higher) was associated with the downregulation of HvPsbR gene encoding one of the extrinsic proteins of the Oxygen Evolving Complex. The reduced expression of HvPsbR might lead to the impairment of the OEC action, manifested by the occurrence of the K-band in an analysis of fluorescence kinetics after MeJA treatment as well as reduced photosynthesis efficiency. Furthermore, methyl jasmonate treatment caused a decrease in the nitrogen content in barley leaves, which was associated with an increased expression the four tonoplast aquaporin genes (HvTIP1;2, HvTIP2;2, HvTIP4;1 and HvTIP4;2) predicted to transport the nitrogen compounds from the vacuole to the cytosol. The upregulation of the nitrogen-transporting HvTIPs might suggest their involvement in the vacuolar unloading of ammonia and urea, which both could be remobilised when the nitrogen content in the leaves decreases. Our research provides tips on physiological role of the individual TIP subfamily members of aquaporins under methyl jasmonate action.

Ethylenediaminetetraacetic Acid (EDTA) Mitigates the Toxic Effect of Excessive Copper Concentrations on Growth, Gaseous Exchange and Chloroplast Ultrastructure of Corchorus capsularis L. and Improves Copper Accumulation Capabilities.

Copper (Cu) is an important micronutrient for a plant’s normal growth and development. However, excess amount of Cu in the soil causes many severe problems in plants—which ultimately affect crop productivity and yield. Moreover, excess of Cu contents causes oxidative damage in the plant tissues by generating excess of reactive oxygen species (ROS). The present experiment was designed to investigate the phytoextraction potential of Cu, morpho-physiological features and biochemical reaction of jute (Corchorus capsularis L.) seedlings using ethylenediaminetetraacetic acid (EDTA) of 3 mM under different Cu levels (0 (control), 50 and 100 μM) in a hydroponic nutrient solution (Hoagland). Our results showed that elevated Cu rates (50 and 100 μM) in the nutrient solution significantly reduced plant height, fresh and dry biomass, total chlorophyll content and gaseous exchange attributes in C. capsularis seedlings. As the concentration of Cu in the medium increased (50 and 100 μM), the level of malondialdehyde (MDA) and oxidative stress in C. capsularis seedlings also increased, which could have been controlled by antioxidant activity in particular plant cells. In addition, rising Cu concentration in the nutrient solution also increased Cu uptake and accumulation in roots and leaves as well as affected the ultrastructure of chloroplast of C. capsularis seedlings. The addition of EDTA to the nutrient solution significantly alleviated Cu toxicity in C. capsularis seedlings, showing a significantly increase in plant growth and biomass. MDA contents was not significantly increased in EDTA-induced plants, suggesting that this treatment was helpful in capturing ROS and thereby reducing ROS in in C. capsularis seedlings. EDTA modification with Cu, although the bioaccumulation factor in roots and leaves and translocation factor for the leaves of C. capsularis seedlings has significantly increased. These results indicate that C. capsularis has considerable potential to cope with Cu stress and is capable of removing a large quantity of Cu from the Cu-contaminated soil while using EDTA is a useful strategy to increase plant growth and biomass with Cu absorption capabilities.

Leaf nutrient homeostasis and maintenance of photosynthesis integrity contribute to adaptation of the pea mutant SGECd<sup>t</sup> to cadmium

Cadmium (Cd) is a highly toxic and widespread soil pollutant, which negatively affects various aspects of plant growth and physiology. Here, the role of photosynthesis in response to Cd was investigated in the Cd-tolerant pea (Pisum sativum L.) mutant SGECdt. The wild type SGE and the mutant SGECdt were grown in a hydroponic solution supplemented with 1, 3, or 4 µM CdCl2 for 12 d. Root and shoot biomasses of the Cd-treated SGECdt were significantly higher than of SGE. Cadmium had little effect on the quantum yield of photosystem II (φPSII) and chlorophyll content of intact leaves of both pea genotypes. However, when leaf slices were taken from Cd-exposed plants and incubated with high Cd concentrations, the SGECdt mutant showed 1.5-2 times higher φPSII values than SGE, with genotypic differences maximal at 0.1 and 1 mM CdCl2. In contrast, when leaf slices were taken from plants previously unexposed to Cd, both pea genotypes exhibited similar φPSII values. Cadmium content in leaves and mesophyll protoplasts of Cd-treated SGECdt were about 2-3 times higher than in SGE ones. The mutant leaves and mesophyll protoplasts had also higher Ca, Mg, Mn, and Zn content. Thus, SGECdt acclimated to Cd during growth in the Cd-supplemented nutrient solution by developing a molecular mechanism related to photosynthetic integrity. A higher foliar nutrient content likely allows enhanced photosynthesis by counteracting the damage of leaves caused by Cd.

Root Development and Anti-Oxidative Response of Rice Genotypes under Polyethylene Glycol Induced Osmotic Stress

Osmotic stress is a kind of stress which is directly or indirectly related to all other abiotic stresses. Four rice varieties namely Binadhan-11 (with SUB1 gene), BRRI dhan52 (with SUB1 gene), Binadhan-7 and BRRI dhan71 were used to study the variation in root development and anti-oxidative response under osmotic stress conditions. Osmotic stress was induced by applying polyethylene glycol (4% PEG) in hydroponic solution. Treatment was given at the panicle initiation stage and leaf samples were collected at fourteen days after treatment to estimate antioxidant response in terms of ascorbate (APX) and peroxidase (POD) enzymatic activity. Roots were destructively harvested at 16 days after the stress imposition. The tested varieties showed significant differences in antioxidant responses under the stress condition such as high APX and POD in Binadhan-11 and BRRI dhan52. Significant injury at the 4 th leaf position (the youngest leaf was the reference) was observed at 8 and 12 days after the treatment. Number of live leaves, shoot dry weight, density of second order lateral roots, number of phytomer (Pr) and total roots, number of roots at Pr2, main axis diameter at Pr1, main axis length at Pr1 varied significantly among the varieties × treatment combinations. Binadhan-11 and BRRI dhan52 showed comparatively higher osmotic stress tolerance compared to the other two varieties without SUB1 gene, viz., Binadhan-7 and BRRI dhan71. The varieties BRRI dhan52, and Binadhan-11 showed greater capacity to withstand osmotic stress can be further used to develop stress tolerant variety.

Strontium Uptake and Effects in Hydroponically Cultivated Celery

The artificial radionuclide 90Sr is the main radionuclide in radioactive environmental pollution. In this study, celery was cultured in a laboratory hydroponics system for 21 days with strontium (Sr) levels of 0 (control), 0.5, 1, 2.5, 5, and 10 mM. The changes in the Sr contents in celery leaves and roots as well as the translocation factor (TF) values (ratio of the Sr concentration in aerial plant parts to that in roots) under different Sr concentrations were studied. Additionally, the effects of Sr stress on the absorption of six nutrients, the chlorophyll content, and the biomass of the celery were investigated. The results showed that the Sr contents in celery leaves and roots increased with the increasing Sr concentration in the hydroponic solution, but the increase of the Sr concentration in roots slowed under the 10 mM Sr treatment. The mean TF values ranged from 0.40 ± 0.01 to 1.12 ± 0.17. With the increase in Sr concentration in the hydroponic medium, the contents of calcium, iron, and potassium in the celery leaves were significantly reduced, and the absorption of calcium, iron, and magnesium by roots was significantly inhibited. Compared with the control, sulfur concentration in celery roots increased significantly under the Sr treatments increasing except the 10 mM Sr treatment. The changes in chlorophyll content were consistent with those of celery biomass, and the values of both these parameters were high under the 5 mM Sr treatment.

Exogenous Melatonin Improves Salt Tolerance by Mitigating Osmotic, Ion, and Oxidative Stresses in Maize Seedlings

Melatonin has been confirmed extensively for the positive effects on increasing plant tolerance to various abiotic stresses. However, the roles of melatonin in mediating different stresses still need to be explored in different plants species and growth periods. To investigate the role of melatonin in mitigating salt stress, maize (Zea mays L.) seedlings growing in hydroponic solution were treated with 100 mM NaCl combined with or without 1 μM melatonin. Melatonin application had no effects on maize growth under normal condition, while it moderately alleviated the NaCl-induced inhibition of plant growth. The leaf area, biomass, and photosynthesis of melatonin-treated plants were higher than that of without melatonin under NaCl treatment. The osmotic potential was lower, and the osmolyte contents (including sucrose and fructose) were higher in melatonin-treated plants. Meanwhile, the decreases in Na+ content and increases in K+/Na+ ratio were found in shoots of melatonin-applied plant under salt stress. Moreover, both enzymatic and nonenzymatic antioxidant activities were significantly increased in leaves with melatonin application under salt treatment. These results clearly indicate that the exogenous melatonin-enhanced salt tolerance under short-term treatment could be ascribed to three aspects, including osmotic adjustment, ion balance, and alleviation of salt-induced oxidative stress.

The ZIP Transporter Family Member OsZIP9 Contributes To Root Zinc Uptake in Rice under Zinc-Limited Conditions.

Zinc (Zn) is an important essential micronutrient for plants and humans; however, the exact transporter responsible for root zinc uptake from soil has not been identified. Here, we found that OsZIP9, a member of the ZRT-IRT-related protein, is involved in Zn uptake in rice (Oryza sativa) under Zn-limited conditions. OsZIP9 was mainly localized to the plasma membrane and showed transport activity for Zn in yeast (Saccharomyces cerevisiae). Expression pattern analysis showed that OsZIP9 was mainly expressed in the roots throughout all growth stages and its expression was upregulated by Zn-deficiency. Furthermore, OsZIP9 was expressed in the exodermis and endodermis of root mature regions. For plants grown in a hydroponic solution with low Zn concentration, knockout of OsZIP9 significantly reduced plant growth, which was accompanied by decreased Zn concentrations in both the root and shoot. However, plant growth and Zn accumulation did not differ between knockout lines and wild-type rice under Zn-sufficient conditions. When grown in soil, Zn concentrations in the shoots and grains of knockout lines were decreased to half of wild-type rice, whereas the concentrations of other mineral nutrients were not altered. A short-term kinetic experiment with stable isotope 67Zn showed that 67Zn uptake in knockout lines was much lower than that in wild-type rice. Combined, these results indicate that OsZIP9 localized at the root exodermis and endodermis functions as an influx transporter of Zn and contributes to Zn uptake under Zn-limited conditions in rice.

Fabrication and performance evaluation of A shaped frame hydroponic system for leafy garlic

Present study was carried out for Fabrication and Performance Evaluation of A Shaped frame Hydroponic System under Protected Structures at the Centre of Excellence on Protected Cultivation and Precision Farming (CoE-PCPF), College of Agriculture, IGKV, Raipur (C.G.) during the year 2017-18. The experiment was laid out with three treatments T1 (A-frame PVC pipe), T2 (A-frame UPVC pipe), T3 (A-frame CPVC pipe), of hydroponic system. The transplanting of seedlings of leafy garlic was done in perforated net pots with a media of coco-pit and vermiculite in 3:1 proportion and clay pellets. Irrigation was applied to the crop by ebb flow technique. The pH and EC of the hydroponic solution were maintained in the range of 5.5 to 6.5 and 1.5 to 2.5 dS/m respectively in the tank. Hydroponic system in the present study has been fabricated with the help of locally available material which reduced cost of construction substantially. Effects of material on the growth of plants, EC and pH level of nutrient solution have also been studied and it is found that material has a very little or no effect on the growth as well as EC and pH aspects of nutrient solution at least in the first year of cultivation which might be changed in later years. Appearance wise good and moderately costlier UPVC pipes can be a better option for the design and construction of commercial hydroponic systems. Cost analysis of fabricated hydroponic Structure was also done.

Cadmium isotope fractionation reveals genetic variation in Cd uptake and translocation by Theobroma cacao and role of natural resistance-associated macrophage protein 5 and heavy metal ATPase-family transporters

In response to new European Union regulations, studies are underway to mitigate accumulation of toxic cadmium (Cd) in cacao (Theobroma cacao, Tc). This study advances such research with Cd isotope analyses of 19 genetically diverse cacao clones and yeast transformed to express cacao natural resistance-associated macrophage protein (NRAMP5) and heavy metal ATPases (HMAs). The plants were enriched in light Cd isotopes relative to the hydroponic solution with Δ114/110Cdtot-sol = −0.22 ± 0.08‰. Leaves show a systematic enrichment of isotopically heavy Cd relative to total plants, in accord with closed-system isotope fractionation of Δ114/110Cdseq-mob = −0.13‰, by sequestering isotopically light Cd in roots/stems and mobilisation of remaining Cd to leaves. The findings demonstrate that (i) transfer of Cd between roots and leaves is primarily unidirectional; (ii) different clones utilise similar pathways for Cd sequestration, which differ from those of other studied plants; (iii) clones differ in their efficiency of Cd sequestration. Transgenic yeast that expresses TcNRAMP5 (T. cacao natural resistance-associated macrophage gene) had isotopically lighter Cd than did cacao. This suggests that NRAMP5 transporters constitute an important pathway for uptake of Cd by cacao. Cd isotope signatures of transgenic yeast expressing HMA-family proteins suggest that they may contribute to Cd sequestration. The data are the first to record isotope fractionation induced by transporter proteins in vivo.

Morphological Responses and Gene Expression of Grain Amaranth (Amaranthus spp.) Growing under Cd.

Phytoremediation efficiency depends on the ability of plants to accumulate, translocate and resist high levels of metals without symptoms of toxicity. This study was conducted to evaluate the potential of grain amaranth for remediation of soils contaminated with Cd. Three grain amaranth varieties, “Pribina” (A. cruentus), “Zobor” (A. hypochondriacus x A. hybridus) and Plainsman (A. hypochondriacus x A. hybridus) were tested under different level of Cd (0, 5, 10 and 15 mg/L) in a hydroponic experimental treatment. All could be classified as Cd excluders or Cd-hypertolerant varieties able to grow and accumulate significant amounts of Cd from the hydroponic solution, preferentially in the roots. Under the highest level of Cd exposure, qRT-PCR expression analysis of five stress-related genes was examined in above- and below-ground biomass. The results show that the Cd concentration significantly increased the mRNA level of chitinase 5 (Chit 5) in amaranth roots as the primary site of metal stress. The involvement of phytochelatin synthase (PCS1) in Cd detoxification is suggested. Based on our findings, we can conclude that variety “Pribina” is the most Cd-tolerant among three tested and can be expected to be used in the phytomanagement of Cd loaded soils as an effective phytostabiliser.

Rapid method of screening for drought stress tolerance in maize (Zea mays L.)

Drought stress is the major production constraint in rainfed maize. Screening for drought tolerance is severely affected by the lack of a simple and reliable phenotyping technique. The objective of this study was to standardize a simple hydroponic based drought screening technique in maize. In this context, one week old uniform seedlings of 55 inbreds and 5 hybrids were transferred to hydroponic solution in the glass house. The seedlings were allowed to acclimatize for next one week in hydroponic solution. The drought stress was imposed by removing seedlings from nutrient solution and exposed to air for 6 and 4 hours daily for a period of 5 and 4 consecutive days in hybrids and inbreds, respectively. Data were recorded on all shoot and root parameters, and based on stress symptoms, a drought tolerance score was given to each genotype. The percent deductions in shoot and root fresh weight from non-stress to stress ranged from 11.7 to 84.4 and 2.1 to 77.5, respectively. Six inbred lines, namely, DQL790-4, CML334, CM140, CML422, CM125 and HKI488 and three hybrids namely DMRH1306, DMRH1410 and PMH4 were found drought tolerant. The effectiveness of this screening technique was compared and confirmed using pots screening as well as by expression profiling of key antioxidant genes (Sod2, Sod4, Sod9 and Apx1) playing role in drought stress tolerance. This phenotyping technique is very short, low cost and simple which can be utilized in preliminary drought screening for large set of maize germplasm and mapping populations.

Characterizing Nutrient Composition and Concentration in Tomato-, Basil-, and Lettuce-Based Aquaponic and Hydroponic Systems

Aquaponic nutrient studies often use various types of water containing high levels of mineral nutrients for water supply, making it difficult to accurately determine deficient nutrients limiting crop yield and quality across the systems. To avoid interference with background nutrients, we used reverse osmosis water in this study. The objectives were to identify critical nutrients that affect the yield and quality of cherry tomato-, basil-, and lettuce by characterizing nutrient composition and concentration in aquaponic systems in comparison to hydroponic systems. Daily release rate (mg L−1) of macronutrients derived from fish feed (41% protein, 1.1% phosphorus, 1% fish weight) was in decreasing order of SO4–S (16) > PO4–P (2.4) > NO3–N (1.0) > K (0.8) > Cl (0.5) > NH4–N (0.4) > Ca (0.2) > NO2–N (0.13) > Na (0.11) > Mg (0.02), in which daily inputs of Mg and Ca in aquaponics were found to be only 1–2% and 4–6%, respectively, of those in hydroponics. Subsequently, the average concentrations of all nutrients were significantly lower in aquaponics than in hydroponics during a 3-month production except for Cl, NH4–N, NO2–N, and Na. The concentration of Mg remained below 5 mg L−1 in all aquaponic systems, while the concentration of Ca rapidly decreased in tomato-based aquaponics, especially during fruiting. SPAD value (chlorophyll content) was associated with concentrations of leaf N, Mg, and/or Ca. Specifically, lower SPAD value was correlated with lower leaf Mg and Ca for tomato and lower leaf Mg for basil but neither Mg nor Ca for lettuce. The aquaponic solution contained nearly six-times higher Na than the hydroponic solution, resulting in three-times higher Na concentration in the edible portion of the crops. Compared to a lettuce-based aquaponic system, tomato- and basil-based systems retained more desirable water quality parameters (i.e., stable pH, lower temperature), had lower electrical conductivity (EC) via greater biomass production and, therefore, more efficient nutrient removal, and had lower feed conversion rate and higher fish biomass increment. Regardless of crop species, vegetative shoot biomass was significantly reduced in aquaponics than in hydroponics. However, the marketable yield of tomatoes was similar between aquaponics and hydroponics, while those of basil and lettuce were reduced in aquaponics by 56% and 67%, respectively, in comparison to hydroponics. Our results highlighted potential solutions to design proper nutrient management practices essential for the development of successful aquaponic production systems. Considering that ingested fish feed does not provide sufficient levels of Mg and/or Ca for crop production, it is suggested to supplement Mg before crop transplanting and Ca before fruiting of fruity crops to improve crop growth and quality in aquaponic systems, especially when high-quality water is used for water supply.

Uptake and Translocation of Perfluorooctanoic Acid (PFOA) and Perfluorooctanesulfonic Acid (PFOS) by Wetland Plants: Tissue- and Cell-Level Distribution Visualization with Desorption Electrospray Ionization Mass Spectrometry (DESI-MS) and Transmission Electron Microscopy Equipped with Energy-Dispersive Spectroscopy (TEM-EDS).

Perfluoroalkyl substances (PFASs) are persistent chemicals in the environment. So far, little is known about their uptake potential in wetland plants. Here, we investigated the uptake and translocation of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in eight common wetland plants, namely, Canna indica (Ci), Thalia dealbata (Td), Cyperus alternifolius (Ca), Phragmites australis (Pa), Arundo donax (Ad), Pontederia cordata (Pc), Cyperus papyrus (Cp), and Alisma orientale (Ao) by hydroponic experiments and visualized their tissue- and cell-level distribution with desorption electrospray ionization mass spectrometry (DESI-MS) and transmission electron microscopy equipped with energy-dispersive spectroscopy (TEM-EDS). The results showed that the PFASs accumulated in plants accounted for 1.67-16.7% of the total mass spiked into the hydroponic systems, and PFOS accumulated largely in roots (48.8-95.8%), while PFOA was stored mostly in the aboveground part (29.3-77.4%). DESI-MS and TEM-EDS analysis showed that PFASs in Ci, Td, Pa, and Ca were transported from the hydroponic solution to the root cortex via both apoplastic (e.g., across cell walls and/or intercellular spaces) and symplastic routes (e.g., across plasma membranes or via plasmodesmata) and further to the vascular bundle via symplastic route in Td and Pa and via both routes in Ci and Ca. These two chemicals were transported from roots to stems mainly through the cortex in Td and through both the cortex and vascular bundles in Ci and Ca.

The Beneficial Effects of Aluminum on the Plant Growth in Camellia japonica

The aim of this research was to investigate the effect of aluminum (Al) on the plant growth, nutrient uptake, and Al accumulation in Camellia japonica. A hydroponic experiment was performed in a completely randomized design with four concentration of Al (0, 0.5, 1, and 2 mM). After growing 8 weeks in the hydroponic nutrient solution, the fine roots and mature leaves of plants were sampled to analyze the biomass, photosynthetic parameters, nutrients uptake, and Al accumulation. The 0.5, 1, and 2 mM Al supplement presented an increase of 71, 118, and 42% on the root biomass, respectively, comparing to the control. The Al-induced growth stimulation in 0.5 and 1 mM Al treatment of Camellia japonica was associated with increased levels of chlorophyll a and b, promotion of net photosynthesis rate, raised contents of soluble sugar and total soluble protein, and decreased levels of malondialdehyde (MDA) and free proline in both leaves and fine roots. The concentrations of nitrogen (N), phosphorus (P), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in fine roots of 1 mM Al-treated plants were significantly higher than those in the control plants, whereas the levels of calcium (Ca) and magnesium (Mg) were much lower. The mean Al levels in the 1 mM Al-treated plants were 1587, 7189, and 11,192 mg kg−1 (dry mass, DW) for the 1st/2nd, 3rd/4th mature leaves, and fine roots, respectively. This study indicated that 0.5 and 1 mM Al were beneficial to the growth of Camellia japonica. This Al-induced growth enhancement was presumably associated with the increased uptake of nutrient elements. This study also confirmed Camellia japonica as an Al-accumulator.