In addition, this opens the possibility of customising the buffer species and mixtures added, so that the amounts or proportions of the positive ion portion of the buffer delivered to the system may be adjusted or controlled by choosing buffer species or mixtures based on the buffering capacity of the negative ion. Conductivity continually increases in fish-only systems because of the build-up of ions which are produced as the by-products of fish metabolism. The inclusion of plants into recirculating aquaponic systems leads to active uptake of waste nutrients and ions by the plants, which counteracts the ionic build-up seen in fish-only systems. The efficiency of plants to take up nutrients and ions in hydroponic systems, and thus maintain zero conductivity accumulation within system waters, is dependent upon whether the correct mix and concentrations of those nutrients are provided. The conductivity curves from the present study indicate that, in the final third of the experiment, plants within the mixed and potassium treatments maintained slightly lower water conductivities than observed in control or calcium treatments, although overall conductivities did not differ significantly between any treatments across the 21-day course of the research-scale experiment. This apparent lowering of conductivity levels in the last third of the experiment for the mixed and potassium treatments is probably since plants within these treatments had access to increased levels of potassium during their fastest-growing phase.
Potassium is an essential macronutrient to plants and is known to play a key role in a plant’s ability to synthesise proteins and carbohydrates,and thus grow. Adler, Harper, Takeda, et al. also argued that when other nutrients limit plant growth, nutrient removal can be increased by adding those nutrients that are most limiting, and therefore, rolling benches other essential nutrients must be added to the aquaponic system. These nutrients typically include iron, manganese and potassium. The lowered conductivities in the two treatments containing higher additions of potassium may suggest that the plants in these treatments had a slightly increased ability to achieve elevated carbohydrate and protein synthesis, thus allowing them to remove and assimilate slightly greater amounts of ions from the surrounding water medium and therefore, lowering the conductivity of the system water. This hypothesis also may be supported by the observation that lettuce plants within these two potassium-containing treatments exhibited the highest growth rates and yields and exhibited the greatest removal rates of nitrate from recirculating waters. In terms of water use, results suggest that those treatments containing potassium were also more efficient,with significantly less water used by the potassium and mixed test treatments, when compared to the control treatment. Again, this result is probably correlated with the plant’s requirement for potassium to achieve carbohydrate and protein synthesis and subsequent growth. The plant’s requirement to transpire more water from those treatments not containing additional potassium may be explained by the fact that the plants may have been transpiring greater amounts of water to try and gain greater access to limiting ions, such as potassium. In conclusion, results from the present study suggest that, when using buffers for maintenance and control of pH in recirculating aquaponic systems, it is advantageous to use buffers with positive ion constituents that are essential to optimal plant growth. Parameters such as plant growth and yield, nitrate removal, conductivity and water use demonstrate that either a potassium-based buffer or a mixture of potassium and calcium-based buffers are the most appropriate buffers to use to achieve optimal plant growth efficiencies in the research-scale aquaponic system, whilst parameters such as fish growth and FCR, dissolved oxygen and pH maintenance are unaffected by the positive ion make-up of the buffer.
In addition, it is apparent from buffer use and pH maintenance parameters that the negative ion constituent of the buffer may affect the amount of buffer required. It is therefore recommended that this work be replicated at a commercial scale and through an entire fish production cycle and that future aquaponic researchers and industry individuals use buffers containing potassium as the positive ion constituent and consider periodically using calciumbased buffers to maintain pH in recirculating aquaponic systems.Plan factories are facilities that enable the year-round production of vegetables and other productions through precise control of the growth condition. The practical implementation of such facilities is needed to decrease its costs. Controlling circadian rhythm is one of optimizing idea to solve the problem of cost. Plant circadian rhythms are composed of a large number of genes. Expressions of these genes build complex feedback loop.The circadian rhythms have important functions in physiological processes of plants including photosynthesis and growth. Therefore precise control of circadian rhythms is able to become a key technology for plant production in artificial environments such as plant factory. When we measure the luciferase bioluminescence to observe circadian rhythm, the sample what is small seedling or cut leaf inside petri dish is used mainly. However, the cut leaf will change brownish or die after some days. In the leaf of the lettuce, the bioluminescence damps and cannot be measured by its degradation. In addition, a cut leaf is able to grow only to some size into the petri dish. From these reasons, we cannot observe the circadian rhythm in each stage of growth and the responses to the controlled light conditions in the long term. Unfortunately, we have one more problem which LUC bioluminescence only can be measured from the genetically modified lettuce. The lettuce is modified luciferase reporter gene which fused clock gene was used in this experiment and a firefly luciferase gene into. The genetically modified plants emit bioluminescence in proportion to the expression of CCA1. We cannot treat it for food. Therefore we paid our attention to the delayed fluorescence of the lettuce. In this study, DF is the light which is emitted immediate after illuminated sample by light emitting diode. When photosynthesis is done, DF is emitted mainly from chlorophyll. DF reflects the physiological state in plant and can be measured in any wild type plant in real time. Therefore it can be one of important indicator of circadian rhythm. However, it is not studied the simultaneous measurement from the same individual because DF has lower bioluminescence intensity than LUC bioluminescence, these spectrums are adjacent each other and the intensity damps exponentially. Because of these reasons, spectrometry is not able to apply to measure of DF and LUC bioluminescence. Therefore, we developed the devise which measured LUC bioluminescence and DF from lettuce, which cultivated in the state that nearer to vertical farming, at the same time in the long term.Atrazine is a widely used triazine herbicide over the world. However, studies show that ATZ affects the human endocrine system, lymphatic system, immune system, and reproductive system, and may induce malformations and organism mutations. Although ATZ has been included in the list of endocrine disruptor compounds by the United States, Japan and the European Union and other countries, it is still registered for use in many countries due to its excellent herbicidal efficacy and low price. Therefore, the research on the safety of ATZ’s ecological environment is imminent.
Alfalfa is a kind of forage with high ecological value because of its strong adaptability and regeneration ability. In addition, its root system has nitrogen fixation ability, which can increase the content of soil organic matter and improve the physical and chemical properties of soil. Our previous research has shown that alfalfa has the potential to remediate ATZ contamination. However, excessive pesticide exposure often causes plants to produce some toxic reactions. Chlorophyll content, cell membrane permeability, and accumulation of reactive oxygen species are commonly used evaluation indicators. Our previous study showed that the accumulation capacity of ATZ in rice leaves at different ages was different,but the mechanism of accumulation on toxic effects is still unclear. Metabolism of pesticides is one of the important ways for plants to slow down the toxic effects. The phase II metabolism of pesticides in plants requires the consumption of certain endogenous compounds such as glutathione and glucose, which may disrupt the balance of endogenous metabolites in plants. Cysteine S-conjugates and homoglutathione/glutathione S-conjugates are the major metabolites of ATZ in plants. Therefore, studying the regulation of ATZ on differentially expressed metabolites and differentially expressed genes in Cys and GSH metabolism pathways and DEGs related to the generation/elimination of reactive molecular species in alfalfa is of great significance for the cultivation of ATZ-resistant plant varieties and the construction of transgenic plants with high remediation ability. At present, the research on the fate of organic pollutants in plants is limited to the metabolic process in plants,but the excretion of metabolites by roots is rarely reported. Root exudates refer to various substances released by plant roots into the surrounding environment. A large number of studies have reported that roots can excrete organic acids, phenolic substances, polysaccharides, enzymes and other substances in response to different rhizosphere environmental changes. It is not clear whether the metabolites of ATZ can also be excreted to the external environment and which metabolites can be excreted. The excretion of pesticide metabolites by roots is closely related to the safety of the ecological environment.Per- and polyfluoroalkyl substances are a group of anthropogenic aliphatic fluorinated chemicals that have been used globally due to their hydrophobic and lipophobic properties. PFASs are persistent in the environment and accumulative in wildlife and humans. Perfluorooctane sulfonate is one of the well-known PFAS in scientific literature.
It was listed in the Stockholm Convention on Persistent Organic Pollutants in 2009. PFOS was phased out from production and commerce/use in most applications in several countries. Similarly, perfluorooctanoic acid and long-chain perfluorocarboxylic acids are believed to be on track to be phased out. Consequently, some substitutes for PFOS/PFOA have emerged, including shorter-chain compounds, ether-PFAS,and fluorotelomers. In particular, 6:2 fluorotelomer sulfonamide alkylbetaine is an amphoteric PFAS currently used in consumer and industrial products. It was reported in Dupont’s Capstone 1157 surfactant and AFFFs from Angus Fire,Fire Service Plus, and National Foam. 6:2 FTAB has been detected in various environment media, such as groundwater,soil,earthworms,river water,and sediments. 6:2 FTAB was detected in the surface soil of the long-term fire training site at a high concentration of up to 66,305 ng/g dry weight. Earlier studies demonstrated that PFCA precursors could be taken up by plants from soil/solution and biotransformed to downstream metabolites. 6:2 FTSA, which is also a common PFOS alternative, ebb and flow bench could be bioaccumulated by pumpkin and then biotransformed to stable products, such as PFHpA, PFHxA, PFPeA, PFBA, PFPrA and TFA. 10:2 fluorotelomer alcohol could be taken up in wheat and metabolized to PFPeA, PFHxA and perfluorodecanoate in root while PFDA and perfluoroundecanoic acid in shoot. 6:2 FTOH and 8:2 FTOH could be accumulated by plants, and then transformed to intermediate metabolites and terminal products, such as fluorotelomer saturated acids,fluorotelomer unsaturated carboxylic acids and PFCAs. Therefore, 6:2 FTAB may be transferred and degraded in plants and further contribute to human exposure through the food chain. However, studies on bioaccumulation and biotransformation of 6:2 FTAB in plants are not reported to date. The biotic and abiotic degradation of 6:2 FTAB has been investigated by several previous studies. The main photochemical degradation intermediate of 6:2 FTAB was 6:2 fluorotelomer sulfonamide,followed by 6:2 FTSA, 6:2 fluorotelomer sulfonamide alkylamine,6:2 FTOH and 6:2 FTUCA, and a large amount of PFCAs have also been observed. In addition to abiotic degradation, the biotic metabolisms of 6:2 FTAB were also investigated, showing different degradation pathways. The main metabolites of 6:2 FTAB biodegraded by strain NB4–1Y isolated from vermicompost were 5:2 fluorotelomer ketone,6:2 FTCA, 6:2 FTOH and 5:2 sFTOH, while 5:3 FTCA, 4:3 FTCA, PFHxA, PFPeA and PFBA were detected at low concentrations. Previous aerobic biodegradation test showed that biodegradation of 6:2 FTAB produced 6:2 FTOH, 6:2 FTCA, 6:2 FTUCA, 5:3 FTCA, 6:2 FTSAm and short-chain PFCAs in the presence of either active or sterilized aerobic sludge, whereas 6:2 FTSA was measured with sterilized sludge only. In addition, 6:2 FTAB could be extensively metabolized in blue mussel and turbot, with 6:2 FTAA being its major metabolite. Formation of 6:2 FTAA, 6:2 FTSAm and 6:2 FTSA indicated that 6:2 FTAB was metabolized in zebrafish. Although it has been confirmed that 6:2 FTAB could be degraded by animals and microorganisms, studies on its transformation mechanism in plants are still limited. It has been demonstrated that 6:2 FTAB had lower bioaccumulation capacity in zebrafish than that of 6:2 FTAA. Previous studies also reported that 6:2 FTAB had toxicity effects on aquatic organisms. The juvenile turbot exposed to 6:2 FTAB was identified that genes involved in the digestion and immune system were suppressed at the transcriptional level. 6:2 FTAB induced developmental toxicity in zebrafish embryos, such as cell apoptosis, oxidative stress and immunotoxicity. 6:2 FTAB and 6:2 FTAA coexposure could disrupt the adult endocrine system and impaired offspring development in adult zebrafish.