Article

Effects of hypochlorite as a disinfectant for hydroponic systems on accumulations of chlorate and phytochemical compounds in tomatoes

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Abstract

Recently, official food surveillance discovered high residues of chlorate (ClO3 −) and perchlorate (ClO4 −) in different plant-based foods, which was the start of a big discussion in the EU Commission. There is currently no knowledge about possible ClO3 − uptake quantities in vegetable, when hypochlorite (ClO−) is used as a disinfectant in plant production facilities. Therefore, the present study is focused on the identification of interactions between ClO− applications and ClO3 − accumulations in fruit, as well as findings in terms of suitable concentrations of ClO− to ensure food safety. Primary and secondary metabolites were analyzed as well. As such, on-site produced potassium hypochlorite (1 % KClO) solution was supplemented using proportional injection control once a week for 90 min, as a disinfectant, into a recirculating tomato production system (NFT) until a free chlorine concentration of 1 mg L−1 (D I) and 2 mg L−1 (D II) was reached, respectively. The chlorate (ClO3 −) content in fruit increased from 0.01 mg (Control) to 0.22 mg (D I) and 0.25 mg ClO3 − kg−1 FW (D II). A critical assessment of these values is given in the discussion section. Contrary to the expectations, a co-occurrence of ClO3 − and ClO4 − in fruit was not found. Compared to the control, the fruit contents of lycopene were increased by 21.3 % (D I) and 33.5 % (D II) and those of ß-carotene by 9.2 % (D I) and 23.9 % (D II), when calculated on a fresh weight basis. These results changed slightly when these substances were calculated on a dry weight basis. Furthermore, ClO3 − induced stress in fruit. In this context, a significant correlation (r) and a significantly increased slope (m) compared to zero were found between ClO3 − and lycopene (r = 0.74; m = 0.10), as well as ß-carotene (r = 0.70; m = 0.01). The content of soluble solids and that of titratable acids remained unaffected. http://rdcu.be/mHBZ

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... As to how chlorate arrives in the food, among the reasons considered are application of chlorinated irrigation and washing water in pre-and post-harvest periods (kaufmann-hOrlacher 2014). There is already evidence in this respect that circulating irrigation water (NFT technique) with a chlorine disinfection using electrolytically produced hypochlorite (ClO − ) can lead to concentration of chlorate in tomatoes (Dannehl et al. 2015a). The disinfection procedure applicable can feature application of commercially available chlorine bleach liquor (sodium hypochlorite) delivered in barrels, as well as disinfectant substances produced via on-site systems. ...
... Hereby, it has been proved in the meantime that the electrolytic disinfection of irrigation water can lead to chlorate absorption by vegetables. In the corresponding study (Dannehl et al. 2015a), tomato plants were continuously irrigated within a closed circuit on plastic channels (NFT) with a disinfectant solution produced on site and dosed discontinuously over a period of three months (1/week for 90 min) in concentrations of 1 mg (variant DI) or 2 mg free chlorine/l (variant DII) in fertiliser-containing irrigation water (contents including ammonia). In the result, no yield reduction was determined while antimicrobial efficacy was found to be improved (Dannehl et al. 2015B). ...
... In the result, no yield reduction was determined while antimicrobial efficacy was found to be improved (Dannehl et al. 2015B). However, the chloride content in water rose following discontinuous introduction of disinfectant by 14 mg/l (DI) on average, or 21 mg/l (DII) (Dannehl et al. 2015a), whereby the crop growing recommendation for hydroponic tomatoes of < 532 mg chloride/l (SOnneVelD and StraVer 1988) was undersupplied, even after three months without water change. All the same, the tomatoes also tolerated, compared to other hydroponic crops (e.g. ...
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Article
To the background of discussions on problematical residues in plant-derived foods, the procedure for minimising chlorate content in the electrolytic disinfection of irrigation water is of great importance. As a source of adjustment recommendations was investigated, on the basis of a brine electrolysis plant (single chamber system), how much chlorate is produced during the electrochemical production procedure for the disinfectant solution and how its proportion changes during storage under warm greenhouse conditions. Investigated additionally was the effect the plant fertiliser ammonia has on disinfectant substances. Consequently, minimising chlorate in the electrolytic water disinfection could be achieved by using a cooling system for the electrolysis reactor and the disinfectant storage tank. Additionally recommended is a short term storage tank for the disinfectant solution. Regarding dosage of disinfectant solution, it was shown that ammonia markedly increases usage of disinfectant or chlorate input into the irrigation water. It is therefore recommended that dosage be controlled by chlorine sensor so that alterations of chemical processes in water (e.g. chlorine loss) can be accounted.
... Conventional and emerging water treatment technologies have been compared for their efficacy for pathogen removal (Diao et al., 2004;Kerwick et al., 2005;Li et al., 2011), albeit primarily in drinking water applications. There is notable research that explores using electrochemical disinfection methods in hydroponics (Bakheet et al., 2020;Bandte et al., 2016;Dannehl et al., 2016;Rodriguez et al., 2018); however, much of this research focusses on electrochemical methods to produce concentrated chlorine on site, which is then inject into the solution. To our knowledge, there are no studies on integrating electrochemical hypochlorination to treat fertigation water in situ within closed-loop hydroponics. ...
... Chloride levels were shown to remain relatively stable over a growth period of 21 days and subsequent nutrient solution replenishment. This aspect is a significant advantage over injection systems, which have been shown to have a 4-fold increase over a period of 80 days when injecting free chlorine at 0.04 mmol/L (Dannehl et al., 2016). Furthermore, the concentration of Clhas an influence on NO 3 uptake within plants (Neocleus et al., 2021) and the in situ treatment could stabilize the desired Cllevels for longer periods of time. ...
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Article
Capturing and reusing fertigation drainage is a key strategy for maximizing greenhouse production efficiency while minimizing the impact of wastewater discharge on receiving ecosystems. Fertigation drainage, in this regard, refers to irrigation water mixed with fertilizer that has once passed through soilless culture. Although an economically and environmentally prudent practice, recirculating fertigation solutions does pose an increased risk of pathogen proliferation. There are many water disinfection technologies currently available to growers, including ozone (O3(aq)) and Advanced Oxidation Processes (AOP). Beyond currently available treatment options there are emerging technologies that have yet to be optimized for recirculating hydroponics. Electrochemical systems based on Dimensionally Stable Anodes (DSA) offer a novel method for disinfecting fertigation. Using Cyclamen persicum as a representative greenhouse floriculture crop, fertigation solutions were inoculated with Fusarium oxysporum isolated from a diseased C. persicum sample. Following inoculation, solutions were treated with one of either a DSA electrochemical system, a UV/Ozone AOP system, or ozonation. Solutions were then applied to the crop and disease progression was monitored. The positive control group (F. oxysporum added) exhibited pathogenicity following the recirculation of the fertigation solution, while the negative control (F. oxysporum absent) did not show pathogenicity in C. persicum. All water treatment systems achieved a log-4 reduction in F. oxysporum, which prevented pathogenicity in plants. Furthermore, there were no significant differences in plant physiology between the water treatment methods in comparison to the negative control group. However, all treatments performed significantly better than the positive control group which experienced pathogenicity. Solution nutrient analysis indicated stability across all treatments. Energy consumption was also monitored and demonstrated a two-fold reduction in electricity use with the electrochemical flow cell (EFC) compared to the AOP system.
... Nitsopoulos, Glaumer, and Friedle (2014) demonstrated the systemic uptake of chlorate in lettuce irrigated with drinking water containing low amounts of chlorate (0.043 mg L −1 ). Reports on electrolyzed water to disinfect irrigation water for use in greenhouses have described that chlorate accumulated in hydroponic tomatoes (0.25 mg kg −1 ) (Dannehl, Schuch, Gao, Cordiner, & Schmidt, 2016) and also in sprinkler irrigated baby leaves (< 0.10 mg kg −1 ) López- Gálvez et al., 2018a). A higher accumulation has been reported in baby spinach cultivated in open field (up to 0.99 mg kg −1 ) when treated irrigation water with chlorine dioxide (ClO 2 ) (López-Gálvez, Gil, Meireles, Truchado, & Allende, 2018b). ...
... Food Control 114 (2020) 107283 once present in the water (Alfredo, Adams, Eaton, Roberson, & Stanford, 2014). The risk associated with the presence of chlorate is not restricted to reclaimed water, as several studies related to chlorine disinfection treatments for reservoir or well water reported the occurrence of chlorate in the irrigated crops (Dannehl et al., 2016;López-Gálvez et al., 2018b;Nitsopoulous et al., 2014). During this study, another field was also sampled in the same region where reclaimed water intended for irrigation from a MWTP was treated with ultraviolet (UV) light as antimicrobial treatment. ...
Article
The use of reclaimed water for irrigation after disinfection can provide significant environmental, social and economic benefits and solve the problem of water scarcity. The occurrence of disinfection by-products (DBPs) as pollutants in irrigation water has been highlighted as a health risk of emerging concern since they can be uptaken by the plant and accumulated in the edible parts during crop production. Little attention has been paid to the occurrence of chlorate in reclaimed water when using chlorine as a tertiary disinfection treatment. This study aimed at evaluating if chlorine-treated reclaimed water from a Municipal Wastewater Treatment Plant resulted in the accumulation of chlorate in commercially grown romaine lettuce. The risk of accumulation in the edible parts of the head was also examined by comparing the internal, middle, and external leaves as well as the roots. The results showed that the irrigation with chlorinated reclaimed water resulted in the accumulation of chlorate in fresh lettuce (0.34–0.56 mg kg⁻¹), despite that the chlorate content in irrigation water was below the maximum residual level (MRL) allowed for potable water (0.25–0.49 vs. 0.70 mg L⁻¹, respectively). The chlorate content gradually increased from the inner leaves (younger) (0.21 mg kg⁻¹) to the outer leaves (oldest) (0.55 mg kg⁻¹), and the roots (0.56 mg kg⁻¹). This study shows that there was chlorate bioconcentration observed in fresh lettuce heads, although it did not exceed the current maximum residue levels for chlorate on leafy greens (0.7 mg kg⁻¹) established in the amended Regulation (EC) No 396/2005 (SANTE/10684/2015 Rev. 9) recently adopted. However, the use of chlorate-free disinfectants as antimicrobial agents for the irrigation of edible crops with a low level antimicrobial residual to protect water in distribution systems is recommended to reduce the chlorate intake by consumers.
... The accumulation of DBPs in plants and potential health effects also need to be carefully considered (Dannehl, Schuch, Gao, Cordiner, & Schmidt, 2016;L opez-G alvez, Andujar, et al., 2018) and this is an area that would benefit from more research. Dannehl et al. (2016) found that using potassium hypochlorite as the disinfectant in a recirculating hydroponic system, resulted in higher chlorate content in the tomatoes being grown than the current European maximum residue limit. ...
... The accumulation of DBPs in plants and potential health effects also need to be carefully considered (Dannehl, Schuch, Gao, Cordiner, & Schmidt, 2016;L opez-G alvez, Andujar, et al., 2018) and this is an area that would benefit from more research. Dannehl et al. (2016) found that using potassium hypochlorite as the disinfectant in a recirculating hydroponic system, resulted in higher chlorate content in the tomatoes being grown than the current European maximum residue limit. Similarly, overhead irrigation with EO treated water resulted in accumulation of chlorates in lettuce to above the maximum residue limit (L opez-G alvez, Andujar et al., 2018). ...
Article
The growing health and economic burden posed by foodborne pathogens has stimulated global interest in the development of safe, affordable, effective and environmentally-sustainable irrigation water treatment technologies. This review critically compares the potential of existing and emerging methods for disinfection of irrigation water to reduce pathogenic microbial loads on high-risk vegetables and minimally processed fresh produce. We explore electrochemical disinfection and electrolyzed oxidizing water as alternatives to traditional chlorination, and identify hydrodynamic cavitation as an emerging disinfection strategy worthy of further investigation in this context. In addition, we assess the state of the knowledge regarding the impact of current water sanitation strategies on the ecological dynamics of plant and soil microbes and the potential induction of viable but nonculturable cells. Increased research in these areas could translate into substantial improvement in the overall quality and value of fresh produce, while maintaining environmentally-sustainable irrigation water usage.
... Although the generation of disinfection by-products after wastewater treatment doesn't directly impact human health, but the release of such wastewater into water bodies may adversely impact the aquatic life. Use of treated wastewater disinfected with chlorine for irrigation may also result in accumulation of chlorates (OCl 3 À ) in plants (Dannehl et al. 2016). These chlorates are generated as degradation by-products in chlorinated wastewaters (Zhong et al. 2019). ...
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Article
Though chlorine is a cost-effective disinfectant for water and wastewaters, the bacteria surviving after chlorination pose serious public health and environmental problems. This review critically assesses the mechanism of chlorine disinfection as described by various researchers; factors affecting chlorination efficacy; and the re-growth potential of microbial contaminations in treated wastewater post chlorination to arrive at meaningful doses for ensuring health safety. Literature analysis shows procedural inconsistencies in the assessment of chlorine tolerant bacteria, making it extremely difficult to compare the tolerance characteristics of different reported tolerant bacteria. A comparison of logarithmic reduction after chlorination and the concentration-time values for prominent pathogens led to the generation of a standard protocol for the assessment of chlorine tolerance. The factors that need to be critically monitored include applied chlorine doses, contact time, determination of chlorine demands of the medium, and the consideration of bacterial counts immediately after chlorination and in post chlorinated samples (regrowth). The protocol devised here appropriately assesses the chlorine-tolerant bacteria and urges the scientific community to report the regrowth characteristics as well. This would increase the confidence in data interpretation that can provide a better understanding of chlorine tolerance in bacteria and aid in formulating strategies for effective chlorination.
... Studies also show its utility to control algae biofilm formation in greenhouses (Dannehl et al., 2015). Nevertheless, a drawback of this disinfection method is possible initiation of unwanted chlorate in fruits such as tomatoes (Dannehl et al., 2016). It is shown, that minimization of chlorate is difficult but possible (Schuch et al., 2016a, b). ...
Article
Tested in experimental scale, an innovative system for electrolytic water disinfection in greenhouses (SeWiG) was very efficient. It was developed by Humboldt-Universität zu Berlin and newtec Umwelttechnik GmbH. With scaling up this system for industrial greenhouses, the new technology will be tested, validated and optimized under practical conditions. The implemented technology will be incrementally scaled-up. After successful installation of the disinfection system within a separated part of an industrial greenhouse, two large-scaled greenhouses will use the on-site produced hypochlorite as a disinfectant for irrigation or drain water applied for vegetables and ornamental plants. The effects on plant growth, yield and product quality will be controlled and particular attention is paid to chlorate and perchlorate. Due to the first results, both pesticides are under the limits given by the European Commission. This can be related to the short dwell time of the disinfectant before dosing based on the on-demand production of fresh hypochlorite. Hypochlorite is dosed by the method of shock disinfection, which might decrease the accumulation of unwanted ingredients in plants. The special feature of the new system for electrolytic water disinfection is the functional superiority over common methods such as filtration, ultraviolet irradiation, heating, ozonation or chlorine dioxide. Worth highlighting is its high effectiveness against plant viruses and the reduced risk for users, plants and the environment while less energy is needed, compared to other disinfection systems. Besides a reduced formation of algae biofilm, a reduced application of fertilizers is expected. All parameters mentioned before will be monitored within this study.
... It is assumed that these residues are caused by the application of chlorine-containing disinfectants during post-harvest processes. Recently, Dannehl et al. (2016) reported on a highly significant correlation between the chlorate-accumulation in tomatoes and the application of hypochlorite as a disinfectant for hydroponic systems, although they classified the consumption of those tomatoes as harmless because maximum residue levels for chlorate (EFSA, 2015) were not exceeded. Nevertheless, we demonstrate here that with the use of ORP sensor-controlled dosing application of hypochlorite can be optimised, and combined with following the recommendations of Schuch et al. (2016) for the generation of electrolytically-derived hypochlorite, this should keep risks of chlorate accumulation low. ...
Article
Demand for conservation and recycling of water has increased significantly. Therefore irrigation water used for horticultural or agricultural purposes needs to be treated before being reused to eradicate plant pathogens and thereby reducing the risk of pathogen dispersal and losses due to disease. The economically important fungal plant pathogens Fusarium oxysporum (Synder and Hans) and Rhizoctonia solani (Kühn) were selected to examine the efficacy of nutrient solution treatment by electrolytic disinfection to prevent the dispersal of these pathogens in the hydroponic production of tomatoes (Solanum lycopersicum Mill.). First, we determined the efficacy of the disinfectant to inactivate F. oxysporum and R. solani in vitro. The electrolytically generated potassium hypochlorite (KClO) was tested at five concentrations of free chlorine (0.2, 0.5, 0.8, 1.0, 2.0 mg/L) in nutrient solutions of pH 5.5, 6.0 and 6.5 with four contact times (5, 30, 60, 120 min). Best sanitation was achieved in nutrient solution at pH 6.0. In vitro, F. oxysporum required 2 mg/L at 30 min for complete inactivation whereas chlorination had only a minimal effect on viability of R. solani. Subsequent trials under practical conditions applied the disinfectant via a new sensor-based disinfection procedure. Potassium hypochlorite solution produced on site and injected into a recirculating nutrient solution once a week for 60 min at a free chlorine concentration of 0.5 mg/L (ORP 780 mV) inhibited the dispersal of F. oxysporum and R. solani during the entire test period of 16 weeks. In contrast all tomato test plants irrigated with untreated nutrient solution became infected with F. oxysporum and a third of them additionally with R. solani. At the applied dose no plant damage occurred. Thus, the treatment proved to be effective and applicable to prevent dispersal of fungal pathogens by nutrient solution under simulated field conditions.
... For this reason, disinfection of the solution is essential, although direct administration of pesticides into the solution has been prohibited at law (Ministry of Agriculture, Forestry and Fisheries, 2010). Therefore, it is desired to establish safe and effective alternative disinfection methods, and the various disinfection treatments have been investigated, including UV light, heat, the titanium dioxide photocatalytic reaction, and ozone (O 3 ) (Bando et al., 2008;Dannehl et al., 2016;Ehret et al., 2001;Igura et al., 2004;Koohakan et al., 2003;Ohtani et al., 2000;Runia, 1995). However, these treatments still are not put into any practical use in terms of the efficiency, treatment time, and running cost. ...
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Article
To investigate the difference in the disinfectant efficiency of ozone microbubbles (O3MB) and ozone millibub-bles (O3MMB), the morphological change of the treated Fusarium oxysporum f. sp. melonis spores was observed with scanning and transmission electron microscopies (SEM and TEM). The disinfectant efficiency of O3MB on F. oxysporum f. sp. melonis spores was greater than that of O3MMB. On observation with SEM, it was revealed that morphological change of F. oxysporum f. sp. melonis spores was caused by O3MB and O3MMB, and damage to the spore surfaces by O3MB occurred sooner than that by O3 MMB. On observation with TEM, it was furthermore confirmed that F. oxysporum f. sp. melonis spores treated with O3MB induced wavy deformation of cell membrane and the intracellular change different from that with O3MMB. Therefore, the greater disinfection efficiency of O3MB was suggested to be caused due to the function of the MB in addition to the oxidative power of O3.
... It is assumed that these residues are caused by the application of chlorine-containing disinfectants during post-harvest processes. Recently, Dannehl et al. (2016) reported on a highly significant correlation between the chlorate-accumulation in tomatoes and the application of hypochlorite as a disinfectant for hydroponic systems, although they classified the consumption of those tomatoes as harmless because maximum residue levels for chlorate (EFSA, 2015) were not exceeded. Nevertheless, we demonstrate here that with the use of ORP sensor-controlled dosing application of hypochlorite can be optimised, and combined with following the recommendations of Schuch et al. (2016) for the generation of electrolytically-derived hypochlorite, this should keep risks of chlorate accumulation low. ...
Article
Demand for conservation and recycling of water has increased significantly. Therefore irrigation water used for horticultural or agricultural purposes needs to be treated before being reused to eradicate plant pathogens and thereby reducing the risk of pathogen dispersal and losses due to disease. The economically important fungal plant pathogens Fusarium oxysporum (Synder and Hans) and Rhizoctonia solani (Kühn) were selected to examine the efficacy of nutrient solution treatment by electrolytic disinfection to prevent the dispersal of these pathogens in the hydroponic production of tomatoes (Solanum lycopersicum Mill.). First, we determined the efficacy of the disinfectant to inactivate F. oxysporum and R. solani in vitro. The electrolytically generated potassium hypochlorite (KClO) was tested at five concentrations of free chlorine (0.2, 0.5, 0.8, 1.0, 2.0 mg/L) in nutrient solutions of pH 5.5, 6.0 and 6.5 with four contact times (5, 30, 60, 120 min). Best sanitation was achieved in nutrient solution at pH 6.0. In vitro, F. oxysporum required 2 mg/L at 30 min for complete inactivation whereas chlorination had only a minimal effect on viability of R. solani. Subsequent trials under practical conditions applied the disinfectant via a new sensor-based disinfection procedure. Potassium hypochlorite solution produced on site and injected into a recirculating nutrient solution once a week for 60 min at a free chlorine concentration of 0.5 mg/L (ORP 780 mV) inhibited the dispersal of F. oxysporum and R. solani during the entire test period of 16 weeks. In contrast all tomato test plants irrigated with untreated nutrient solution became infected with F. oxysporum and a third of them additionally with R. solani. At the applied dose no plant damage occurred. Thus, the treatment proved to be effective and applicable to prevent dispersal of fungal pathogens by nutrient solution under simulated field conditions.
... This mixture was shaken vigorously for 10 min, centrifuged for 5 min at 2,500 rpm, filtered and directly analysed using LC-MS/MS (Agilent 1290 Infinity LC coupled with an Agilent 6460 triple quadrupole MS/MS; Agilent Technologies GmbH; Waldbronn, Germany). Injection volume, used column, eluents, flow rate, flowing gradient and the ion mode are described in detail by Dannehl et al. (2016). Quantification of chlorate was performed via an internal standard and expressed as mg ClO3 -kg -1 FW. ...
Article
The research was focused on the identification of interactions between hypochlorite used as a disinfectant for a recirculating tomato production system and the spread of microorganisms, plant characteristics and fruit quality. Potassium hypochlorite (1% KCLO) supplemented once a week for 90 min into different nutrient solution ranks until a free chlorine concentration of 1 mg L-1 (DI) and 2 mg L-1 (DII) caused benefits but also hazards. Results showed that microorganisms were suppressed by up to 100%. Plants exposed to treatment DI showed a comparable plant height in comparison to control plants, whereas this plant parameter was significantly increased by 12 cm caused by treatment DII after a growing period of seven weeks. However, the formation of leaves was more pronounced by treatment DI. This was obviously the main reason for an increase in yield by 10% (DI) calculated in comparison to control plants. While phytotoxic problems can be excluded, the chlorate (ClO3-) content in tomatoes increased from 0.01 mg (control) to 0.22 mg (DI) and 0.25 mg (DII) ClO3- kg-1 fresh weight. This enhancement should be seen as critical value because new maximum residue levels (MRL) will be defined next year. The levels of lycopene increased with increasing concentrations of hypochlorite as well, which was probably based on a stress response owing to the accumulation of chlorate. Apart from the ClO3- accumulations in fruit, treatment DI represents the most promising disinfection for recirculating tomato production systems.
... Such contamination can occur at various stages of the food production chain: already during cultivation, harvesting or processing, for example through the use of chlorinated water or chlorinated disinfectants. Ref. [65] showed a highly significant correlation between the application of hypochlorite and chlorate accumulation in tomatoes. Fortunately, the accumulation of both chlorate and perchlorate was not found in tomato fruits following electrolytic disinfection of fertigation solution. ...
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Article
Shortage of water availability and awareness of the need for sustainable resource management have generated a significant increase in the use of recycled water for irrigation and processing of crops and harvest products, respectively. As a result, irrigation systems face the challenge of neutralizing plant pathogens to reduce the risk of their dispersal and the subsequent occurrence of diseases with potentially high economic impacts. We evaluated the efficacy of an innovative electrolytic disinfection system based on potassium hypochlorite (KCLO) to inactivate major pathogens in hydroponically grown tomatoes: Fusarium oxysporum (Synder and Hans), Rizocthonia solani (Kühn), Tobacco mosaic virus (TMV) and Pepino mosaic virus (PepMV). The electrolytically derived disinfectant was prepared on-site and added to the recirculating fertigation solution once a week for 60 min in an automated manner using sensor technology at a dosage of 0.5 mg of free chlorine/L (fertigation solution at pH 6.0 ± 0.3 and ORP 780 ± 31 mV). Tomato fruit yield and pathogen dispersal were determined for 16 weeks. At the applied dosage, the disinfectant has been shown to inhibit the spread of plant pathogenic fungi and, remarkably, plant viruses in recirculating fertigation solutions. Phytotoxic effects did not occur.
... Therefore, placing an in-situ disinfecting nutrient solution is essential. Several methods have been applied for the disease control in recirculating soilless culture systems such as: ozone, ultraviolet, filtration, chemical sterilization and radiation and biological control [3][4][5][6][7][8] . ...
... Recently, the maximum residue levels for chlorate have been regulated in fresh produce (EC, 2020c) and also in drinking water when a disinfection method that generates chlorate is used (0.7 mg L − 1 ) (EC, 2020b). Chlorinated irrigation water is the main factor contributing to chlorate residues in the crop (Dannehl et al., 2016;López-Gálvez et al., 2018a). If chlorine-treated wastewater is used for irrigation, the maximum residue levels (MRLs) regulated can be exceeded due to the continuous uptake of chlorate by the crop during the growth (EC, 2020c). ...
Article
A case study of 15 wastewater treatment plants (WWTPs) at a full-scale was assessed for the risks of disinfection byproduct (DBP) formation, mainly the regulated trihalomethanes (THMs) and haloacetic acids (HAAs) and chlorate as an inorganic byproduct regulated recently in the EU. Raw wastewater from large, medium/small urban areas were treated with single or combined disinfection processes (i.e., chlorine, peracetic acid (PAA) and ultraviolet (UV) radiation). Sampling was executed once a month over seven months for the medium/small WWTPs and twice a month for the large ones. Due to the potential risk of SARS-CoV-2 contaminated wastewater, several inactivation methods were examined before the DBP analysis. Due to the inactivation step, the stability of THM4 and HAA9 suffered reductions, monitoring their presence only in the effluents after the disinfection treatments. In contrast, chlorate levels remained unchanged after the inactivation treatment; thus both raw wastewater and effluents were examined for their occurrence before disinfection treatments. Results showed that chlorate residues in the raw wastewater varied greatly from undetected levels to as high as 42.2 mg L⁻¹. As the continuous monitoring of DBPs was performed, a positive correlation with chlorine or chlorine/UV was found. Changes in the physicochemical parameters indicated that the quality of the raw wastewater varied considerably depending on the WWTPs, and it influenced byproduct formation. In all WWTPs, chlorine alone or combined with UV significantly increased the presence of THMs, HAAs, and chlorate levels in the treated effluents. When the same WWTPs changed to PAA or PAA/UV, DBPs were diminished completely. This study highlights the risk of chlorate residues in raw wastewater during the pandemic. It also showed how the chemical risks of DBP formation could be reduced by changing the chlorinated disinfection technologies to PAA or PAA/UV, particularly if reclaimed water is intended for agricultural irrigation to minimize DBP residues.
... Zur Frage, durch welche verfahrenstechnischen Prozesse das Chlorat in Lebensmittel gelangt, wird u. a. der Einsatz von gechlortem Gieß-und Waschwasser in der Vor-und Nachernte vermutet (kaufmann-hOrlacher 2014). Hierzu erfolgte bereits der Nachweis, dass eine Chlordesinfektion mit elektrolytisch hergestelltem Hypochlorit (ClO − ) bei zirkulierendem Gießwasser (NFT-Verfahren) zur Anreicherung von Chlorat in Tomatenfrüchten führen kann (Dannehl et al. 2015a). Bei dem zugrundeliegenden Desinfektionsverfahren wird entweder handelsübliche Chlorbleichlauge (Natriumhypochlorit) aus Fässern verwendet oder das Desinfektionsmittel wird in Anlagen vor Ort selbst hergestellt. ...
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Article
Die Minimierung von Chlorat bei der elektrolytischen Gießwasserdesinfektion ist aufgrund problematischer Chloratrückstände in pflanzlichen Lebensmitteln von Bedeutung. Im Hinblick auf verfahrenstechnische Optimierungsvorschläge wurde daher am Beispiel einer Salzelektrolyseanlage (Einkammersystem) geprüft, wie viel Chlorat beim Herstellungsprozess des Desinfektionsmittels entsteht und wie sich dessen Anteil bei einer Lagerung unter warmen Temperaturbedingungen im Gewächshaus verändert. Zudem wurde untersucht, wie sich der Pflanzendünger Ammonium auf das Desinfektionsmittel auswirkt. Dabei ergab sich, dass die Chloratbildung durch eine Kühlung des Elektrolysereaktors sowie des Desinfektionsmitteltanks und durch ein zur Kurzzeitlagerung ausgelegtes Bevorratungssystem von Desinfektionsmittel minimiert werden könnte. Ferner wurde bestätigt, dass Ammonium den Desinfektionsmittelverbrauch bzw. Chlorateintrag deutlich erhöht. Daher empfiehlt sich eine sensorbasierte Dosierung, um sich ändernde chemische Vorgänge im Gießwasser (Chlorzehrung) zu berücksichtigen.
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Technical Report
Im Produktionsgartenbau besteht bei geschlossener Bewässerung ein erhöhtes Verbreitungsrisiko von wasserübertragbaren Pflanzenkrankheitserregern. Hierzu weisen die gängigen Verfahren zur Wasserdesinfektion zwar eine hohe Effizienz bei der Eliminierung von Pilzen und Bakterien auf, können aber Viren nur mit hohem Energieaufwand (Wärmebehandlung > 90 °C) zuverlässig inaktivieren. Daher wurde das System zur elektrolytischen Wasserdesinfektion in Gewächshäusern (SeWiG) entwickelt und im Rahmen einer DIP-Förderung auf große Praxisgewächshäuser skaliert und optimiert. Das zum Einsatz kommende Desinfektionsmittel wird vor Ort während eines elektrochemischen Prozesses (Salzelektrolyse) erzeugt. Die eigentliche Wasserbehandlung erfolgt durch eine sensorgesteuerte Applizierung mit diskontinuierlicher Dosierstrategie (2-3/Woche), wobei ein desinfektionswirksamer Puffereffekt zur Verringerung des Energie- und Desinfektionsmitteleinsatzes führt. Unter Praxisbedingungen beträgt der Energieverbrauch des Verfahrens lediglich 0,5 kWhel/m³. Zudem ist die Wirksamkeit gegen Pflanzenviren wie Tobacco mosaic virus und Pepino mosaic virus hervorzuheben. Am Beispiel eines tomatenproduzierenden Gewächshausbetriebs ließen sich die mikrobielle Belastung im Drain und der Biofilm in den Bewässerungsrinnen deutlich reduzieren. Hinsichtlich des Einflusses auf die Pflanze trat unter den geprüften Bedingungen keine Ertragsminderung auf und die toxikologisch unbedenkliche Menge an Desinfektionsnebenprodukten (Chlorat, Perchlorat) wurde nicht überschritten (gemäß EFSA-Berechnungsmodell). Mit Projektende sind die Voraussetzungen zur Marktetablierung des Desinfektionsverfahrens gegeben.
Article
Kilang tanaman adalah konsep terbaru dalam industri pertanian di Malaysia, di mana kini kita beralih daripada pertanian berasaskan tanah kepada pertanian di dalam bangunan. Kilang tanaman menggunakan pencahayaan buatan (plant factory with artificial lights) dan sistem pengeluaran tanaman secara tertutup (closed plant production systems) dapat menghasilkan tanaman berkualiti tinggi tanpa sebarang penggunaan racun perosak. Di MARDI, sebuah kilang tanaman berskala perintis telah dibina bagi menghasilkan sayur-sayuran dan herba yang bernilai tinggi. Kehadiran faktor biologi seperti alga, mikroorganisma dan serangga didapati boleh menyebabkan kualiti tanaman terjejas dan mengurangkan hasil pengeluaran. Oleh itu, Prosedur Standard Operasi (SOP) bagi pengurusan faktor biologi di kilang tanaman MARDI telah dibangunkan.
Article
The effects of a 6-h chlorine dioxide sanitation of alfalfa seed (0, 50, 100, and 200 mg/kg seed) on total coliform bacteria, seed germination, and the presence of chlorate and perchlorate residues in seed rinse, seed soak, and alfalfa sprouts was determined. Chlorate residues in 20,000 mg/L calcium hypochlorite, commonly used to disinfect seed, were quantified. Chlorine dioxide treatment reduced (P < 0.05) total coliforms on seeds with no effect (P > 0.05) on germination. Dose-dependent sodium chlorate residues were present in seed rinse (4.1 to 31.2 μg/g seed) and soak (0.7 to 8.3 μg/g seed) waters, whereas chlorate residues were absent (LOQ 5 ng/g) in sprouts, except for 2 of 5 replicates from the high chlorine dioxide treatment. Copious chlorate residues were present (168 to 1260 mg/L) in freshly prepared 20,000 mg/L calcium hypochlorite solution, and storage at room temperature increased chlorate residues significantly (P < 0.01).
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Technical Report
Bei der Nutzung von Oberflächenwasser zur Bewässerung und einer Wiederverwendung des überschüssigen Wassers ist das Verbreitungsrisiko von Pflanzenkrankheitserregern erhöht. Dies bedingt eine effektive Wasserdesinfektion. Hierzu wurde zunächst in vitro die Wirksamkeit einer durch Salzelektrolyse erzeugten Desinfektionslösung zur Inaktivierung von pilzlichen, bakteriellen und viralen Erregern geprüft. Erwartungsgemäß variieren die erforderlichen Chlorkonzentrationen und Einwirkzeiten in Abhängigkeit von der Erregerart. Anschließend wurde die Wirksamkeit in vivo bei Tomatenpflanzen unter Einsatz einer Mess- und Dosieranlage getestet, wobei eine diskontinuierliche Applizierung (1/Woche) des hypochlorithaltigen Desinfektionsmittels zur Unterbindung der Virusverbreitung und zum deutlichen Rückgang von Mikroorganismen im Wasser führte ohne phytotoxische Reaktionen hervorzurufen. Ferner wurde ein Zusammenhang zwischen der Akkumulation von Chlorat und Carotinoiden in Tomaten und der elektrolytischen Wasserdesinfektion festgestellt, wobei nach dem aktuellen Kenntnisstand der Frischgemüseverzehr unter den geprüften Desinfektionsbedingungen als unbedenklich eingestuft werden kann. Das System zur elektrolytischen Wasserdesinfektion in Gewächshäusern (SeWiG) muss nun unter kommerziellen Bedingungen getestet werden und seine Effizienz im Praxisbetrieb unter Beweis stellen. Grundvoraussetzung zur Anwendung im Pflanzenbau ist, dass die toxikologisch unbedenkliche Menge an Desinfektionsnebenprodukten nicht überschritten wird.
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Article
A confined closed greenhouse (CGH) was applied to save energy and to investigate how tomatoes respond to specific microclimatic con-ditions. As such, new dynamic set-points for precise climate control were used in the CGH compared to those applied in a conventional greenhouse. Based on the reduced ventilation frequency in the CGH, the results showed that higher levels of mean temperature, CO2 concentration and relative humidity were achieved. Although the light interception was increased in the CGH, these changing micro-climatic conditions resulted in higher rates of photosynthesis and an associated faster crop growth. This means that the mean plant height was increased by 1.5 m, which was the decisive factor to increase the total yield by 21.4 % in relation to that produced in the conventional greenhouse. The new microclimatic environment caused by the CGH promoted the accumulation of primary and secondary plant compounds in tomatoes such as soluble solids (by 9 %), lycopene (by 22 %), ß-carotene (by 21 %), phenolics (by 8 %) and L-ascorbic acid (by 26 %) compared to conventional produced tomatoes. Compared to existing greenhouse systems, the results suggested that a CGH can be used to produce tomatoes in a sustainable way, where the water use and the energy use efficiency can be improved by 71 % and 43 %, respectively.
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With water conservation and reuse a priority for communities worldwide, recycling irrigation water in commercial plant nurseries and greenhouses is a logical measure. Plant pathogenic microorganisms may be present in the initial water source, or may accrue and disperse from various points throughout the irrigation system, constituting a risk of disease to irrigated plants. The continual recycling of this water is exacerbating this plant disease risk. Accurate and timely detection of plant pathogenic propagules in recycled irrigation water is required to assess disease risk. Both biological and economic thresholds must be established for important plant-pathosystems. Plant pathogens in recycled irrigation water can be managed by a variety of treatment methods that can be arranged in four broad categories: cultural, physical, chemical, and biological. An integrated approach using one or more techniques from each category is likely to be the most effective strategy in combating plant pathogens in recycled irrigation water.
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When a combination of hydrogen peroxide and hypochlorite was used to surface sterilize rice seeds, a 102- to 104-fold decrease in CFU was observed during the first 15 h after inoculation of the rice rhizosphere organismBurkholderia vietnamiensis TVV75. This artifact could not be eliminated simply by rinsing the seeds, even thoroughly, with sterile distilled water. When growth resumed, a significant increase in the frequency of rifampin- and nalidixic acid-resistant mutants in the population was observed compared to the control without seeds. This phenomenon was a specific effect of hypochlorite; it was not observed with hydrogen peroxide alone. It was also not observed when the effect of hypochlorite was counteracted by sodium thiosulfate. We hypothesized that the hypochlorite used for disinfection reacted with the rice seed surface, forming a chlorine cover which was not removed by rinsing and generated mutagenic chloramines. We studied a set of rifampin- and nalidixic acid-resistant mutants obtained after seed surface sterilization. The corresponding rpoB and gyrAgenes were amplified and sequenced to characterize the induced mutations. The mutations in five of seven nalidixic acid-resistant mutants and all of the rifampin-resistant mutants studied were found to correspond to single amino acid substitutions. Hypochlorite surface sterilization can thus be a source of artifacts when the initial bacterial colonization of a plant is studied.
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Effects of NO(2) (-), ClO(3) (-), and ClO(2) (-) on the induction of nitrate transport and nitrate reductase activity (NRA) as well as their effects on NO(3) (-) influx into roots of intact barley (Hordeum vulgare cv Klondike) seedlings were investigated. A 24-h pretreatment with 0.1 mol m(-3) NO(2) (-) fully induced NO(3) (-) transport but failed to induce NRA. Similar pretreatments with ClO(3) (-) and ClO(2) (-) induced neither NO(3) (-) transport nor NRA. Net ClO(3) (-) uptake was induced by NO(3) (-) but not by ClO(3) (-) itself, indicating that NO(3) (-) and ClO(3) (-) transport occur via the NO(3) (-) carrier. At the uptake step, NO(2) (-) and ClO(2) (-) strongly inhibited NO(3) (-) influx; the former exhibited classical competitive kinetics, whereas the latter exhibited complex mixed-type kinetics. ClO(3) (-) proved to be a weak inhibitor of NO(3) (-) influx (K(i) = 16 mol m(-3)) in a noncompetitive manner. The implications of these findings are discussed in the context of the suitability of these NO(3) (-) analogs as screening agents for the isolation of mutants defective in NO(3) (-) transport.
Article
EU legislation, laid down in the Water Framework Directive, demands to minimize emissions of nitrogen, phosphate and crop protection products to achieve an excellent chemical and ecological quality in 2015. The aim is to force growers to a better water and disease management. Supply water of excellent chemical quality will have to be recirculated as long as possible, for which adequate disinfection equipment have to be used. Several sources of water are used as supply water. Rainwater is chemically best, followed by reverse osmosis water. However, the latter is rather expensive. Tap water and surface water often have a too high salinity, while well water may vary dramatically from place to place. Rainwater and surface water are potential risk factors for importing soil-borne pathogens. Disinfection of the recirculating nutrient solution can be done adequately by heat treatment and UV radiation. Membrane filtration performs well, but is mostly too costly. Chemical treatments as sodium hypochlorite, chlorine dioxide and copper silver ionization may partly solve the pathogen problem, but introduce a potential accumulation of other elements in closed systems. Hydrogen peroxide, chlorine dioxide and sodium hypochlorite perform better to clean pipe work instead of soil-borne pathogens.
Article
従来の方法では,トマト果実のクロロフィルとカロテノイド含有量はそれぞれ別の方法で分析されてきた.著者らはトマト色素を同時に定量する簡便な方法を検討した.試料に含まれるすべての色素をアセトンーヘキサン(4:6)で一度に抽出し,上層の663nm, 645nm, 505nm, 453nmの吸光度を分光光度計で同時に測定する.これらの値から著者らの提案した式を用いてクロロフィルa, b,リコペン, β-カロテンの含有量を推定するにとができる.本法を用いて熟度の異なるトマト果実を分析した.また,同じ試料を従来の方法で分析した.その結果,クロロフィル含有量はMACKINNEY法,リコペン含有量は木村らの方法とほぼ同じ値であった.これにより,本法の有効性が確認された.
Article
Based on the fact that several regions worldwide and even in Germany are affected by water deficit problems, a new agronomic approach was developed to produce tomatoes (Solanum lycopersicum L.) in a sustainable way. The main objective of this study was to investigate the effects of a special solar collector greenhouse consisting of finned tube heat exchangers on the quantity and quality of fruit, water use efficiency and water balance. Changing microclimatic conditions in this system positively affected plant physiological processes, resulting in an increased total yield of up to 31.8% and a decreased total water uptake within the crop of up to 29% when compared with a commercial greenhouse. These conditions led not only to a reduction in the amount of nutrient solution (NS) consisting of valuable fresh water but also to increased water use efficiency (+81%). Furthermore, it was found that the finned tube heat exchangers can be considered as a complex water management system, which can be used to collect high quantities of condensation water. It was calculated that a fresh water supplementation used to mix the NS can be completely omitted when the captured rain and condensation water is reused under the conditions in the solar collector greenhouse. In order to test to what extent the collected condensation water was suitable for irrigation, the effects of condensate-containing NS with a higher Zn concentration (1.74 mg L−1) were examined regarding yield and the ingredients in tomatoes. Compared with an applied NS supplemented with 0.2 mg Zn L−1, condensate-containing NS increased fruit quantity (+39%) and quality, e.g., contents of lycopene (+15%), β-carotene (+13%) and phenolic compounds (+12%). Based on the above-mentioned results, it was concluded that a collector greenhouse can be regarded as a useful tool to increase the yield as well as to reduce amounts of fresh water, and the condensation water can safely be reused in hydroponic systems.
Article
Fresh produce such as fruit and vegetables are known carriers of pathogenic microorganisms that often lead to outbreaks of food borne illnesses and public health scares. During the processing of fresh produce strong sanitizers and disinfectants are often required to remove the microbiological load left behind by washing. While such sanitizers and disinfectants must be highly efficacious as an anti-microbial agent, at the same time they must be cost effective, environmentally friendly, non-hazardous to public health and have insignificant effect on the nutritional and organoleptic properties of the fresh produce. This paper reviews the efficacy of various disinfectants to reduce the microbial spoilage and to increase the shelf life of fresh produce without compromising the quality of the end product. Inactivation of microbes using various disinfectants and parameters governing for inactivation are detailed. This review identifies the safest disinfectants that inactive pathogens while maintaining the sensory quality of fresh produce.
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Fresh fruits and vegetables are an essential part of the world populations' diet, contributing essential vitamins and minerals, and they are often eaten raw or minimally processed. Fruits and vegetables grown using conventional agricultural methods are at risk from microbiological contamination and foodborne illness relating to the consumption of produce is widely reported throughout the world, as illustrated by recent figures from the USA (at least 713 produce related outbreaks between 1990 and 2005) and UK (88 outbreaks between 1996 and 2006). Better understanding of produce decontamination is essential to support industry in assuring the safety of fruit and vegetable products, thus contributing to consumer health protection.
Article
The treatment of drinking water with either NaOCl or Ca(OCl)₂ is a source of chlorate ion (ClO₃⁻) in finished water. In basic solution, liquid bleach (NaOCl) decomposition is a second-order process. The decomposition of OC1⁻ involves chlorite ion (ClO₂⁻) as a low-concentration intermediate. The reaction of ClO₂⁻ to form ClO₃⁻ is a fast process, and the ClO₂⁻ in liquid bleach is at a concentration at least 200 times less than the OCl⁻ concentration. The formation of oxygen from decomposing OCl⁻ is a slower side reaction (< 10 percent).
Article
Experiments were carried out to confirm the presence of chlorate ion (C1O₃⁺) in the treated water of utilities that use hypochlorination. Sixteen commercially produced, concentrated liquid hypochlorite feedstocks were analyzed for C1O₃⁺, and levels as high as 158 g percent C1O₃⁺ relative to hypochlorite ion were measured. Finished-water samples from the utilities surveyed contained as much as 0.30 mg C1O₃⁺/L, primarily the result of decomposition of the liquid hypochlorite feedstocks. Although both dilution and lower temperatures can be effective in minimizing C1O₃⁺ formation, it was observed that diluting the initial liquid hypochlorite concentration by a factor of 2 is more effective than decreasing the temperature from 24 to 10°C. A methodology is proposed that predicts the dilution or temperature reduction (or both) required to avoid significant C1O₃⁺ formation in the feedstock solutions. Se llevaron a cabo experimentos para confirmar la presencia del ión de clorato (C1O₃⁺) en aguas tratadas de acueductos que usan hipoclorinación. Se analizaron diez y seis productos de hipocloruro líquido concentrados, producidos comercialmente para definir el C1O₃⁺, y se midieron niveles tan altos como 158 g por ciento de C1O₃⁺ relativos al ión de hipocloruro. Muestras de aguas tratadas de los acueductos estudiados contenían niveles tan altos como 0.30 mg de C1O₃⁺/L, primordialmente como resultado de la descomposición de los productos de hipocloruro líquido. Aunque Ia solución y las bajas temperaturas pueden ser efectivas en minimizar la formación del C1O₃⁺, se pudo observar que al diluir la concentración inicial del hipocloruro líquido por un factor de 2 es más eficiente que disminuir las temperaturas de 24°C a 10°C. Se propone una metodología que predice la dilución o la reducción de la temperatura (o ambos) requerida para evitar la formación del C1O₃⁺ en las soluciones de productos.
Article
This paper presents a simple model for the changes in ion concentration and electrical conductivity (EC) of the recirculating nutrient solution in a closed-loop soilless culture of tomato (Lycopersicon esculentum Mill.). The model was designed on the basis of a balanced equation for plant nutrient uptake: for macrocations (K, Mg and Ca), a linear dependence of concentration on crop water uptake was assumed, while for non-essential ions, such as sodium (Na), a non-linear function was used. The model was developed for closed-loop hydroponic systems in which crop water uptake (namely, transpiration) is compensated by refilling the mixing tank with complete nutrient solution. In these systems, EC gradually increases as a result of the accumulation of macro-elements and, principally, of non-essential ions, like Na, for which the apparent uptake concentration (i.e., the ratio between nutrient and water uptake) is lower than their concentration in the irrigation water. For model calibration, data from both the literature and a previous work were used, while validation was performed with data from original experiments conducted with tomato plants in different seasons and using water with different sodium chloride (NaCl) concentrations (10 and 20 meq/L). The results of validation indicate that the model may be a useful tool for the management of closed-loop hydroponics, because it simulates rather well the salt accumulation that occurs in the recirculating nutrient solution when it is prepared with irrigation water of poor quality. Furthermore, the model is able to estimate the amount of crop evapotranspiration that leads to a value of EC at which flushing is necessary, thus enabling one to predict the water and nitrogen runoff of the semi-closed soilless culture.
Article
The effect of various anions on the short-term influx on NO3− into barley roots was examined by the use of 36ClO3− as a tracer for nitrate. NO3− (36ClO3−) influx was found to be extremely sensitive to inhibition by external Cl− (Ki = 0.035 mM). By contrast 36Cl− influx was not significantly affected by external NO3−. Other anions, SO42− and H2PO4−, had no effect on NO3− (36ClO3−) influx, while HPO42−exerted a slight inhibitory effect. In the range from pH 4 to pH 8 no significant effect of OH− concentration on NO3− (36CIO3−) influx was detected. When barley roots were pretreated for periods up to 4 h with 10 mM NO3−, there was a significant reduction in NO3− (36ClO3−) and 36Cl− influx. KCl at the same concentration (10 mM) caused similar reductions of NO3− (36ClO3−) and Cl− influx. When plants were pretreated with lower NO3− or Cl− concentrations (0.05–5.0 mM) for 2 days, Cl− influx was found to be more sensitive than NO3− (36ClO3−) influx to nitrate or chloride pretreatment.
Article
The effect of electrolyzed water on total microbial count was evaluated on several fresh-cut vegetables. When fresh-cut carrots, bell peppers, spinach, Japanese radish, and potatoes were treated with electrolyzed water (pH 6.8, 20 ppm available chlorine) by dipping, rinsing, or dipping/blowing, microbes on all cuts were reduced by 0.6 to 2.6 logs CFU/g. Rinsing or dipping/blowing were more effective than dipping. Electrolyzed water containing 50 ppm available chlorine had a stronger bactericidal effect than that containing 15 or 30 ppm chlorine for fresh-cut carrots, spinach, or cucumber. Electrolyzed water did not affect tissue pH, surface color, or general appearance of fresh-cut vegetables.
Article
Climate change will lead to an excessive change in climate conditions in greenhouses, particularly during the summer. Therefore, a new climate strategy for greenhouses was developed to avoid plant damages. In this context, interactions between changing microclimatic conditions depending on different climate strategies and plant growth, fruit yield as well as secondary plant compounds were investigated between 2008 and 2009. The results showed that a combined application of a high pressure fog system and CO2 enrichment can be applied to decrease the inside temperature and to increase the levels of relative humidity and CO2 concentrations at a high ambient temperature, accompanied by an increase in mean temperature. Such microclimate in the greenhouse were sufficient to accelerate plant growth, to increase dry matter in leaves, and to promote the formation of fruit set per truss in comparison to those grown under conventional climate conditions. Furthermore, the algorithm of the new climate strategy led to a maximum total yield increase by 20%, to a reduction of blossom-end rot in tomatoes and to a pronounced increase in fruit size during the spring experiments. The climate conditions caused by the new technology significantly promoted secondary metabolism, resulting in a maximum increase in contents of lycopene (by 49%), β-carotene (by 35%), and phenolic compounds (by 16%) as well as associated antioxidant activity in the water-insoluble (by 18.5%) and water-soluble (by 35.4%) fraction compared to the conventional treated plants. Therefore, the new climate strategy may be appropriate to increase the total yield and to improve the fruit quality as well as the health-promoting properties of tomatoes.
Article
The paper begins with a brief review of earlier work.The 1990s saw limited extensions to the theory, computer modelling and practices relating to light transmission, apart from an interesting, but unproven new design to improve transmission. Studies concentrated on improving the performance of greenhouse elements (e.g. cladding), including methods of measurement.Thermal studies show significant progress. Computer modelling was extended to include the time dimension and finite element techniques were used to improve resolution of detail. As with light transmission, studies intended to improve the quality of greenhouse elements were also carried out. Understanding and modelling the performance of a thermal screen has also been improved, both as such and as an integral part of the greenhouse. Much effort was directed towards understanding ventilation. Analysis has shown that different sources exist (thermal-, wind-induced), and these have been analysed. The existence of internal circulating air patterns has also been established.The optimisation of carbon dioxide concentrations in greenhouses has now reached the point where the gain to a grower can be readily predicted.Further computer modelling of light transmission to include the effects of scattering and modelling of skylight to predict leaf irradiance are proposed. Extension of finite element techniques to further improve resolution in thermal studies is recommended. A comprehensive investigation of the physical and engineering aspects of ventilation and internal air flows is also needed, to support the extended thermal studies of the greenhouse. Finally, a pilot study, anticipating the design of a computer-controlled greenhouse is envisaged.
Article
Closed (recirculating) growing systems provide a greater potential for the dispersal of water-borne plant pathogens and disease expression compared to open (run-to-waste) systems. Here we studied the effects of three soilless growing systems (open, closed, and closed with slow sand filtration) on the dispersion of Phytophthora cactorum propagules and the severity of the crown rot disease in strawberry (Fragaria × ananassa Duch.). The plant-growth medium used was coir fiber. The three growing systems showed the same density of P. cactorum propagules in the water drained from the growing media. However, propagules of this pathogen were not detected by the baits in the filtered solution recovered from slow sand filtration. In all systems Phytophthora propagules dispersed from the inoculated plant to adjacent uninoculated plants. At the end of the first crop no differences in the severity of crown rot were found between the different systems of crop culture. However, at the end of the second crop cycle, crown rot in the closed soilless system without slow sand filtration was more severe than in the other two systems. These results demonstrated that the commercial potential of slow sand filtration to prevent propagule dispersal and hence suppress crown rot in strawberry crops grown in a closed culture system.
Article
Lycopene is a potent antioxidant found in watermelon, tomato, and red grapefruit and may exert positive effects on human health. Spectrophotometric and HPLC techniques are commonly employed for analysis of lycopene content in food sources. A rapid and inexpensive spectrophotometric assay for lycopene is presented. This method requires 80% less organic solvents for release and extraction of lycopene from watermelon than do the existing procedures. Comparative analyses for 105 watermelons from 11 cultivars yielded results equivalent to those provided by larger-volume spectrophotometric assay procedures. Limited numbers of assays suggest that this reduced volume method may be applicable for tomatoes and tomato products.
Article
Electrochemical studies were carried out to estimate the risks of perchlorate formation in drinking water disinfected by direct electrolysis. Boron Doped Diamond (BDD) anodes were used in laboratory and commercially available cells at 20 °C. The current density was changed between 50 and 500 A m−2. For comparison, other anode materials such as platinum and mixed oxide were also tested. It was found that BDD anodes have a thousandfold higher perchlorate formation potential compared with the other electrode materials that were tested. In long-term discontinuous experiments all the chloride finally reacted to form perchlorate. The same result was obtained when probable oxychlorine intermediates (OCl−, ClO2−, ClO3−) were electrolysed in synthetic waters in the ppm range of concentrations. The tendency to form perchlorate was confirmed when the flow rate of drinking water was varied between 100 and 300 L h−1 and the temperature increased to 30 °C. In a continuous flow mode of operation a higher chloride concentration in the water resulted in a lower perchlorate formation. This can be explained by reaction competition of species near and on the anode surface for experiments both with synthetic and local drinking waters. It is concluded that the use of electrodes producing highly reactive species must be more carefully controlled in hygienically and environmentally oriented applications.
Article
Several studies have reported on the detection of perchlorate (ClO(4)(-)) in edible leafy vegetables irrigated with Colorado River water. However, there is no information on spinach as related to ClO(4)(-) in irrigation water nor on the effect of other anions on ClO(4)(-) uptake. A greenhouse ClO(4)(-) uptake experiment using spinach was conducted to investigate the impact of presence of chloride (Cl(-)) and nitrate (NO(3)(-)) on ClO(4)(-) uptake under controlled conditions. We examined three concentrations of ClO(4)(-), 40, 220, and 400 nmol(c)/L (nanomoles of charge per liter of solution), three concentrations of Cl(-), 2.5, 13.75, and 25 mmol(c)/L, and NO(3)(-) at 2, 11, and 20 mmol(c)/L. The results revealed that ClO(4)(-) was taken up the most when NO(3)(-) and Cl(-) were lowest in concentration in irrigation water. More ClO(4)(-) was detected in spinach leaves than that in the root tissue. Relative to lettuces, spinach accumulated more ClO(4)(-) in the plant tissue. Perchlorate was accumulated in spinach leaves more than reported for outer leaves of lettuce at 40 nmol(c)/L of ClO(4)(-) in irrigation water. The results also provided evidence that spinach selectively took up ClO(4)(-) relative to Cl(-). We developed a predictive model to describe the ClO(4)(-) concentration in spinach as related to the Cl(-), NO(3)(-), and ClO(4)(-) concentration in irrigation water.
Article
A spontaneous sweet orange (Citrus sinenesis [L.] Osbeck) mutant 'Hong Anliu' is of high value due to lycopene accumulation in the pulp. In this study, we analyzed the proteomic alterations in the pulp of 'Hong Anliu' versus its wild type (WT) at four maturing stages by using 2-DE combined with MALDI-TOF-TOF MS. Among the 74 differentially expressed proteins identified, the majority are predicted to be involved in stress response, carbohydrate/energy metabolism and regulation, or protein fate, modification and degradation. Particularly, expression levels of six anti-oxidative enzymes were altered by the mutation; and assays of their respective enzymatic activities indicated an enhanced level of oxidative stress in 'Hong Anliu', implying a regulatory role of oxidative stress on carotenogenesis. This conclusion was further confirmed by our observation that treatment of fruit pulps with tert-butylhydroperoxide (a ROS progenitor) induced lycopene accumulation in 'Hong Anliu' only. Gene expression showed that genes predicted to function upstream of lycopene biosynthesis were generally upregulated in juice sacs, but downregulated in segment membranes in both 'Hong Anliu' and its WT. The result suggests an important role of post-transcriptional regulation on carotenogenesis since lycopene was induced in 'Hong Anliu' but not WT. The result also implies that carotenogenesis in juice sacs and segment membranes of citrus fruits may be regulated by different mechanisms.
Article
We conducted an epidemiological study in Liguria, Italy, on the association between somatic parameters at birth and drinking water disinfection with chlorine dioxide and/or sodium hypochlorite. Over 2 years (1988-1989), 676 births at two public hospitals, one in Genoa (548 cases) and another in Chiavari (128 cases) were examined and data regarding both mother and child were obtained from hospital records. Results indicate a higher frequency of small body length (< or = 49.5 cm) and small cranial circumference (< or = 35 cm) in infants born to mothers who drank water treated with chlorine compounds. In particular, the statistical analysis (by simultaneous variance analysis and Scheffé test) indicated that there may be an association between infants with smaller body length and mothers who drank water treated with chlorine dioxide [adjusted odds radio (OR) = 2.0; 95% CI = 1.2-3.3] or sodium hypoclorite (adjusted OR = 2.3; 95% CI = 1.3-4.2) and between infants with smaller cranial circumference and mothers who drank water treated with chlorine dioxide (adjusted OR = 2.2; 95% CI = 1.4-3.9) or sodium hypochlorite (adjusted OR = 3.5; 95% CI = 2.1-8.5). The presence of neonatal jaundice is almost twice as likely (adjusted OR = 1.7; 95% CI = 1.1-3.1) in infants whose mothers drank water treated with chlorine dioxide.
Article
Plants have evolved several mechanisms for getting rid of excess energy in photosynthetic membranes, some of which involve isoprenoid compounds. In all photosynthetic organisms, the carotenoids beta-carotene and zeaxanthin, and tocopherols serve an important photoprotective role, either by dissipating excess excitation energy as heat or by scavenging reactive oxygen species (ROS) and suppressing lipid peroxidation. Isoprene and some monoterpenes, diterpenes and other carotenoids also occur in some plant lineages. Compelling evidence indicates that these non-ubiquitous isoprenoids might be particularly relevant in adapting plants to adverse climatic conditions by serving as additional and/or alternative protection mechanisms.
Article
Irrigation with saline water affects tomato fruit quality. While total fruit yield decreases with salinity, inner quality characterized by taste and health-promoting compounds can be improved. For a detailed description of this relationship, the influence of three different salt levels [electrical conductivity (EC) 3, 6.5, and 10] in hydroponically grown tomatoes was investigated. Rising salinity levels in the nutrient solution significantly increased vitamin C, lycopene, and beta-carotene in fresh fruits up to 35%. The phenol concentration was tendentiously enhanced, and the antioxidative capacity of phenols and carotenoids increased on a fresh weight basis. Additionally, the higher EC values caused an increase of total soluble solids and organic acids, parameters determining the taste of tomatoes. Total fruit yield, single fruit weight, and firmness significantly decreased with rising EC levels. Regression analyses revealed significant correlations between the EC level and the dependent variables single fruit weight, total soluble solids, titrable acids, lycopene, and antioxidative capacities of carotenoids and phenols, whereas vitamin C and phenols correlated best with truss number, and beta-carotene correlated best with temperature. Only pressure firmness showed no correlation with any of the measured parameters. As all desirable characteristics in the freshly produced tomato increased when exposed to salinity, salinity itself constitutes an alternative method of quality improvement. Moreover, it can compensate for the loss of yield by the higher inner quality due to changing demands by the market and the consumer. This investigation is to our knowledge the first comprehensive overview regarding parameters of outer quality (yield and firmness), taste (total soluble solids and acids), nutritional value (vitamin C, carotenoids, and phenolics), as well as antioxidative capacity in tomatoes grown under saline conditions.
Article
Although evidence of perchlorate accumulation in plants exists, there is a scarcity of information concerning the key factors and mechanisms involved. To ascertain whether genotypic variation in perchlorate accumulation occurs within lettuce, hydroponic plant uptake experiments were conducted with five types of lettuce (Lactuca sativa L.), which were grown to market size atthree perchlorate (ClO4-) concentrations (1, 5, or 10 microg/L). Perchlorate accumulated in the leafy tissues to varying amounts, ranging from 4 to 192 microg/kg fresh weight (FW), and the ranking of perchlorate accumulation was crisphead > butter head > romaine > red leaf > green leaf. The effect of transpiration rate on perchlorate accumulation was further examined using crisphead, butter head, and green leaf lettuce. By growing lettuce in controlled-environment chambers with two climatic regimes, "cloudy, humid, cool" (80% RH, 18/15 degrees C, 250 micromol/m2s photosynthetic photon flux density (PPFD)) and "sunny, dry, warm" (approximately 50% RH, 28/18 degrees C, 500 micromol/m2s PPFD), up to 2.7-fold differences in transpiration rates were achieved. Across all three genotypes, the plants that transpired more water accumulated more perchlorate on a whole-head basis; however, the effect of transpiration rate on perchlorate accumulation was not as great as expected. Despite 2.0-2.7-fold differences in transpiration rate, there were only 1.2-2.0-fold differences in perchlorate accumulation. In addition to whole-head analysis, plants were sectioned into inner, middle, and outer leaves and processed separately. Overall, the ranking of perchlorate accumulation was outer leaves > middle leaves > inner leaves. Transpiration rate has a clear effect on perchlorate accumulation in lettuce, but other factors are influential and deserve exploration.
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