Anastasis T Christou | Agricultural Research Institute, Cyprus (original) (raw)

Papers by Anastasis T Christou

Nitrogen

The study estimated the relationship between the amount of nitrogen (N) that will become availabl... more The study estimated the relationship between the amount of nitrogen (N) that will become available to plants after incorporation of soil of sheep/goat, cattle, swine, and poultry manure and the duration of manure storage prior to soil addition. Manures were periodically sampled from 12 storage piles that were kept for 12 months each and mixed with soil before laboratory incubation for 83 days. The percentage of organic N mineralized after soil incorporation was clearly greater for poultry, ranging between 41 and 85%, in relation to the other three manure types, for which maximum mineralization ranged between 4.5 and 66%. For sheep/goat, cattle, and swine, the interaction between mineralization and immobilization processes showed a distinct pattern with two phases of net N release during the twelve months of storage. The first was separated from the second by a period where mineralization was zeroed and appeared at about six months after storage initiation. It was recommended that fa...

Agronomy

The sustainability of irrigated agriculture is threatening due to adverse climate change, given f... more The sustainability of irrigated agriculture is threatening due to adverse climate change, given future projections that every one in four people on Earth might be suffering from extreme water scarcity by the year 2025. Pressurized irrigation systems and appropriate irrigation schedules can increase water productivity (i.e., product yield per unit volume of water consumed by the crop) and reduce the evaporative or system loss of water as opposed to traditional surface irrigation methods. However, in water-scarce countries, irrigation management frequently becomes a complex task. Deficit irrigation and the use of non-conventional water resources (e.g., wastewater, brackish groundwater) has been adopted in many cases as part of a climate change mitigation measures to tackle the water poverty issue. Protected cultivation systems such as greenhouses or screenhouses equipped with artificial intelligence systems present another sustainable option for improving water productivity and may he...

Biomolecules

Land plants are continuously exposed to multiple abiotic stress factors like drought, heat, and s... more Land plants are continuously exposed to multiple abiotic stress factors like drought, heat, and salinity. Nitric oxide (NO) and hydrogen sulfide (H2S) are two well-examined signaling molecules that act as priming agents, regulating the response of plants to stressful conditions. Several chemical donors exist that provide plants with NO and H2S separately. NOSH is a remarkable novel donor as it can donate NO and H2S simultaneously to plants, while NOSH-aspirin additionally provides the pharmaceutical molecule acetylsalicylic acid. The current study aimed to investigate the potential synergistic effect of these molecules in drought-stressed Medicago sativa L. plants by following a pharmacological approach. Plants were initially pre-treated with both donors (NOSH and NOSH-aspirin) via foliar spraying, and were then subsequently exposed to a moderate water deficit while NO and H2S inhibitors (cPTIO and HA, respectively) were also employed. Phenotypic and physiological data showed that p...

Journal of pineal research, 2017

Recent reports have uncovered the multifunctional role of melatonin in plant physiological respon... more Recent reports have uncovered the multifunctional role of melatonin in plant physiological responses under optimal and suboptimal environmental conditions. In this study, we explored whether melatonin pretreatment could provoke priming effects in alfalfa (Medicago sativa L.) plants subsequently exposed to prolonged drought stress (7 days), by withholding watering. Results revealed that the rhizospheric application of melatonin (10 μmol L(-1) ) remarkably enhanced the drought tolerance of alfalfa plants, as evidenced by the observed plant tolerant phenotype, as well as by the higher levels of chlorophyll fluorescence and stomatal conductance, compared with nontreated drought-stressed plants. In addition, lower levels of lipid peroxidation (MDA content) as well as of both H2 O2 and NO contents in primed compared with nonprimed stressed plants suggest that melatonin pretreatment resulted in the systemic mitigation of drought-induced nitro-oxidative stress. Nitro-oxidative homeostasis w...

Strawberry plant tissues and particularly fruit material are rich in polysaccharides and polyphen... more Strawberry plant tissues and particularly fruit material are rich in polysaccharides and polyphenolic compounds, thus rendering the isolation of nucleic acids a difficult task. This work describes the successful modification of a total RNA extraction protocol, which enables the isolation of high quantity and quality of total RNA from small amounts of strawberry leaf, root and fruit tissues. Reverse-transcription polymerase chain reaction (RT-PCR) amplification of GAPDH housekeeping gene from isolated RNA further supports the proposed protocol efficiency and its use for downstream molecular applications. This novel procedure was also successfully followed using other fruit tissues, such as olive and kiwifruit. In addition, optional treatment with RNase A following initial nucleic acid extraction can provide sufficient quality and quality of genomic DNA for subsequent PCR analyses, as evidenced from PCR amplification of housekeeping genes using extracted genomic DNA as template. Overall, this optimized protocol allows easy, rapid and economic isolation of high quality RNA from small amounts of an important fruit crop, such as strawberry, with extended applicability to other recalcitrant fruit crops.

Water Research, 2017

Wastewater (WW) reuse for vegetable crops irrigation is regularly applied worldwide. Such a pract... more Wastewater (WW) reuse for vegetable crops irrigation is regularly applied worldwide. Such a practice has been found to allow the uptake of pharmaceutical active compounds (PhACs) by plants and their subsequent entrance to the food web, representing an important alternative pathway for the exposure of humans to PhACs, with potential health implications. Herein we report the impacts of the long-term (three consecutive years) WW irrigation of a tomato crop with two differently treated effluents under real agricultural conditions, on (1) the soil concentration of selected PhACs (i.e. diclofenac, DCF; sulfamethoxazole, SMX; trimethoprim, TMP), (2) the bioaccumulation of these PhACs in tomato fruits, and (3) the human risks associated with the consumption of WW-irrigated fruits. Results revealed that the concentration of the studied PhACs in both the soil and tomato fruits varied depending on the qualitative characteristics of the treated effluent applied and the duration of WW irrigation. The PhAC with the highest soil concentration throughout the studied period was SMX (0.98 μg kg(-1)), followed by TMP (0.62 μg kg(-1)) and DCF (0.35 μg kg(-1)). DCF was not found in tomato fruits harvested from WW-irrigated plants during the first year of the study. However, DCF displayed the highest fruit concentration (11.63 μg kg(-1)) throughout the study (as a result of prolonged WW irrigation), followed by SMX (5.26 μg kg(-1)) and TMP (3.40 μg kg(-1)). The calculated fruit bioconcentration factors (BCFF) were extremely high for DCF in the 2nd (108) and 3rd year (132) of the experimental period, with the respective values for SMX (0.5-5.4) and TMP (0.2-6.4) being significantly lower. The estimated threshold of toxicity concern (TTC) and hazard quotients (HQ) values revealed that the consumption of fruits harvested from tomato plants irrigated for long period with the WW applied for irrigation under field conditions in this study represent a de minimis risk to human health. However, more studies need to be performed in order to obtain more solid information on the safety of WW reuse for irrigation.

Agricultural Water Management, 2016

Water scarcity renders wastewater (WW) reuse for irrigation an increasingly common practice world... more Water scarcity renders wastewater (WW) reuse for irrigation an increasingly common practice world-wide. Comprehensive guidelines and criteria have been established to secure the safety of WW irrigation,especially for food crops or crops that are eaten raw. The aim of this short-term study was to assess theimpacts of strawberry crop irrigation with tertiary treated wastewater (WW) using common irrigationtechniques (Drip, sprinkler, drip under plastic mulch), as compared to potable water (PW) irrigation, onstrawberry fruits’ quality and safety, and on crops’ productivity. The impacts on fruits’ weight and mar-ketability, as well as on fruits’ taste (soluble solids, titratable acidity and soluble solids/titratable acidityratio), antioxidant capacity (ascorbic acid concentration, FRAP, total phenolics and total anthocyanincontent), heavy metal content (Cu, Zn, Mn, Co, Ni) and microbial contamination (total coliform, E. coli,Salmonella spp., Listeria spp), were evaluated. The results revealed that WW irrigation did not signifi-cantly affect the fruits’ marketability, taste and antioxidant capacity, as well as the heavy metal content,in comparison to controlled irrigation, regardless of the irrigation technique applied. Fruits heavy metalcontent was found to be below the maximum permissible levels (MPLs) set for fruit safety, whereas nomicrobiological contamination (total coliform, E. coli, Salmonella spp., Listeria spp.) of fruits was foundin all irrigation water treatments. Overall, the results obtained with regard to the parameters exam-ined highlight the potential for the reuse of the advanced tertiary treated effluent of good quality as avalid alternative for the irrigation of strawberry crops, even with sprinklers. However, further long-termstudies are needed in order for such a practice to be regulated.

Current Opinion in Plant Biology, 2016

Abiotic stresses severely limit crop yield and their detrimental effects are aggravated by climat... more Abiotic stresses severely limit crop yield and their detrimental effects are aggravated by climate change. Chemical priming is an emerging field in crop stress management. The exogenous application of specific chemical agents before stress events results in tolerance enhancement and reduction of stress impacts on plant physiology and growth. However, the molecular mechanisms underlying the remarkable effects of chemical priming on plant physiology remain to be elucidated. Reactive oxygen, nitrogen and sulfur species (RONSS) are molecules playing a vital role in the stress acclimation of plants. When applied as priming agents, RONSS improve stress tolerance. This review summarizes the recent knowledge on the role of RONSS in cell signalling and gene regulation contributing to abiotic stress tolerance enhancement.

Adverse abiotic stress conditions such as drought, salinity, cold, heat and heavy metal toxicity ... more Adverse abiotic stress conditions such as drought, salinity, cold, heat and heavy metal toxicity are considered to be major concerns of the agricultural industry worldwide, as they can affect crop yield and quality, as well as agricultural sustainability in general. Priming of crop plants for more rapid and robust activation of defence reactions offers a means for the effi cient alleviation of the devastating effects induced as a result of exposure to such adverse environmental conditions. Accumulating reports over the recent years postulate a role for hydrogen sulfi de (H 2 S) as an emerging signaling molecule involved in the regulation of physiological processes in plants. In this chapter, we provide a brief overview of recent literature concerning H 2 S biosynthesis and regulation within the plant cell, as well as its involvement in a series of plant physiological processes. Furthermore,

Environmental and Experimental Botany, May 1, 2014

Nitric oxide (NO) and hydrogen peroxide (H 2 O 2 ) have a pivotal role in plant development and s... more Nitric oxide (NO) and hydrogen peroxide (H 2 O 2 ) have a pivotal role in plant development and stress responses, thus rendering them as key molecules for priming approaches. In this study, a hydroponic experiment was employed in order to investigate the effects of NO donor, sodium nitroprusside (SNP; 100 M), or H 2 O 2 (10 mM) root pretreatment in major components of redox homeostasis and signaling of strawberry plants (Fragaria × ananassa cv. 'Camarosa') exposed immediately, or 7 d after root pretreatment, to salt stress (100 mM NaCl, 8 d). Plants stressed immediately after root pretreatment with either reactive species demonstrated increased chlorophyll fluorescence, photosynthetic pigment content, leaf relative water content as well as lower lipid peroxidation and electrolyte leakage levels in comparison with plants directly subjected to salt stress, suggesting a systemic mitigating effect of NO/H 2 O 2 pretreatment to cellular damage derived from abiotic stress factors. In addition, primed plants managed to mitigate the oxidative and nitrosative secondary stress and redox homeostasis disturbances, since H 2 O 2 and NO were quantified in lower levels, whereas ascorbate and glutathione redox states in leaves were sustained at higher rates, compared with NaCl treatment. Gene expression analysis revealed that priming effects of both H 2 O 2 and NO root pretreatment correlated with increased transcript levels of enzymatic antioxidants (cAPX, CAT, GR, MnSOD, MDHAR and DHAR), as well as ascorbate (GaIUR, GLDH, GDH, MIOX) and glutathione biosynthesis (GCS, GS) in leaves, in contrast with the general transcriptional suppression observed in plants stressed without pretreatment, or 7 d after root pretreatment. Overall, pretreated plants displayed redox regulated defense responses leading to systemic tolerance to subsequent salt stress exposure.

Science of The Total Environment, 2016

Pharmaceutically active compounds (PhACs) have been recently shown to exert phytotoxic effects. T... more Pharmaceutically active compounds (PhACs) have been recently shown to exert phytotoxic effects. The present study explores the uptake, systemic translocation, and abiotic stress responses and detoxification mechanisms induced by the exposure of alfalfa plants grown in sand under greenhouse conditions to four common, individually applied PhACs (10μgL(-1)) (diclofenac, sulfamethoxazole, trimethoprim, 17a-ethinylestradiol) and their mixture. Stress physiology markers (lipid peroxidation, proline, H2O2 and NO content, antioxidant activity assays) and gene expression levels of key plant detoxification components (including glutathione S-transferases, GST7, GST17; superoxide dismutases, CuZnSOD, FeSOD; proton pump, H(+)-ATP, and cytochrome c oxidase, CytcOx), were evaluated. PhACs were detected in significantly higher concentrations in roots compared with leaves. Stress related effects, manifested via membrane lipid peroxidation and oxidative burst, were local (roots) rather than systemic (leaves), and exacerbated when the tested PhACs were applied in mixture. Systemic accumulation of H2O2 in leaves suggests its involvement in signal transduction and detoxification responses. Increased antioxidant enzymatic activities, as well as upregulated transcript levels of GST7, GST17, H(+)-ATPase and CytcOx, propose their role in the detoxification of the selected PhACs in plants. The current findings provide novel biochemical and molecular evidence highlighting the studied PhACs as an emerging abiotic stress factor, and point the need for further research on wastewater flows under natural agricultural environments.

Journal of Horticultural Science and Biotechnology

The improvement of plant growth and productivity under biotic and abiotic stress conditions, as w... more The improvement of plant growth and productivity under biotic and abiotic stress conditions, as well as the reduction of post-harvest losses, are of paramount significance for meeting the increasing global population demand for food. Hydrogen sulphide (H2S) has recently appeared as a key contributor towards this goal via its bioactive role in the regulation of plant defence responses. Here, we provide an up-to-date overview of recent literature concerning the biosynthesis and regulation of H2S within the plant cell, as well as its involvement in a series of plant physiological processes. More precisely, H2S is actively associated with growth and developmental processes, tolerance responses following exposure to stress factors in horticultural plants, as well as in post-harvest fruit physiology. The H2S-mediated enhancement of tolerance following exposure of plants to several abiotic stress factors is highlighted, with particular emphasis on the priming effects of H2S on anti-oxidant...

Molecular Approaches in Plant Abiotic Stress, 2013

Agriculture, Ecosystems & Environment, 2014

Advanced tertiary treatment and disinfection technologies have enabled the production of wastewat... more Advanced tertiary treatment and disinfection technologies have enabled the production of wastewater (WW) with quality complying with the established criteria for reuse in agriculture. This study assessed the impacts of tomato crop irrigation with two qualitatively distinct treated WW effluents, as compared to control tubewell water (TW) irrigation, on the soil geochemical properties, tomato fruit safety and crop productivity. The treated effluents reused for irrigation were produced in two Municipal Wastewater Treatment Plants (MWTPs) utilizing two discrete tertiary treatment and disinfection technologies, i.e. Slow Sand Filtration and chlorination (MWTP I), and Membrane Bioreactor and UV radiation (MWTP II), respectively. The impacts on soil pH, electrical conductivity, total organic C, Cl − , NO3 − and heavy metal (Zn, Mn, Ni, Cu, Co) content were evaluated. In addition, the heavy metal content in tomato fruits and leaves, as well as the microbial load in fruit flesh and peel was determined. Crop productivity was measured by the mean fruit weight and maximum diameter, and by the number of fruits per harvest. Irrigation with either WW did not significantly affect the soil pH, organic C and heavy metal content, as well as crop productivity, in comparison to control TW irrigation. Furthermore, the heavy metal content of tomato fruits and leaves in all irrigation treatments was found to be below the maximum permissible levels set for fruit safety and the critical tissue concentration for phytotoxicity, respectively. Moreover, no microbiological contamination (total coliform, fecal coliform, Escherichia coli, Salmonella spp., Listeria spp.) of tomato fruits was found from any irrigation treatment. Overall, results obtained with regard to the parameters examined strongly suggest that advanced tertiary treated effluent of good quality might be safely reused, in terms of both environmental sustainability and public health safety, for vegetable irrigation, concurrently promoting water use efficiency in dry areas.

Environmental Monitoring and Assessment, 2014

An extensive field survey was employed for assessing the impacts of long-term wastewater irrigati... more An extensive field survey was employed for assessing the impacts of long-term wastewater irrigation of forage crops and orange orchards in three suburban agricultural areas in Cyprus (areas I, II, and III), as compared to rainfed agriculture, on the soil geochemical properties and the bioaccumulation of heavy metals (Zn, Ni, Mn, Cu, Co) to the agricultural products. Both ryegrass fields and orange orchards in areas I and II were continuously wastewater irrigated for 10 years, whereas clover fields in area III for 0.5, 4, and 8 years. The results revealed that wastewater reuse for irrigation caused a slight increase in soil salinity and Cl − content in areas I and II, and a remarkable increase, having strong correlation with the period in which wastewater irrigation was practiced, in area III. Soil salinization in area III was due to the high electrical conductivity (EC) of the wastewater applied for irrigation, attributed to the influx of seawater to the sewage collection network in area III. In addition, the wastewater irrigation practice resulted in a slight decrease of the soil pH values in area III, while a subtle impact was identified regarding the CaCO 3 , Fe, and heavy metal content in the three areas surveyed. The heavy metal content quantified in the forage plants' above-ground parts was below the critical levels of phytotoxicity and the maximum acceptable concentration in dairy feed, whereas heavy metals quantified in orange fruit pulp were below the maximum permissible levels (MPLs). Heavy metal phytoavailability was confined due to soil properties (high pH and clay content), as evidenced by the calculated low transfer factor (TF).

Environmental and Experimental Botany, 2014

Journal of experimental botany, 2013

Hydrogen sulfide (H2S) has been recently found to act as a potent priming agent. This study explo... more Hydrogen sulfide (H2S) has been recently found to act as a potent priming agent. This study explored the hypothesis that hydroponic pretreatment of strawberry (Fragaria × ananassa cv. Camarosa) roots with a H2S donor, sodium hydrosulfide (NaHS; 100 μM for 48 h), could induce long-lasting priming effects and tolerance to subsequent exposure to 100mM NaCI or 10% (w/v) PEG-6000 for 7 d. Hydrogen sulfide pretreatment of roots resulted in increased leaf chlorophyll fluorescence, stomatal conductance and leaf relative water content as well as lower lipid peroxidation levels in comparison with plants directly subjected to salt and non-ionic osmotic stress, thus suggesting a systemic mitigating effect of H2S pretreatment to cellular damage derived from abiotic stress factors. In addition, root pretreatment with NaHS resulted in the minimization of oxidative and nitrosative stress in strawberry plants, manifested via lower levels of synthesis of NO and H(2)O(2) in leaves and the maintenance ...

BMC Plant Biology, 2014

Background: Temperature extremes represent an important limiting factor to plant growth and produ... more Background: Temperature extremes represent an important limiting factor to plant growth and productivity. The present study evaluated the effect of hydroponic pretreatment of strawberry (Fragaria x ananassa cv. 'Camarosa') roots with an H 2 S donor, sodium hydrosulfide (NaHS; 100 μM for 48 h), on the response of plants to acute heat shock treatment (42°C, 8 h). Results: Heat stress-induced phenotypic damage was ameliorated in NaHS-pretreated plants, which managed to preserve higher maximum photochemical PSII quantum yields than stressed plants. Apparent mitigating effects of H 2 S pretreatment were registered regarding oxidative and nitrosative secondary stress, since malondialdehyde (MDA), H 2 O 2 and nitric oxide (NO) were quantified in lower amounts than in heat-stressed plants. In addition, NaHS pretreatment preserved ascorbate/glutathione homeostasis, as evidenced by lower ASC and GSH pool redox disturbances and enhanced transcription of ASC (GDH) and GSH biosynthetic enzymes (GS, GCS), 8 h after heat stress imposition. Furthermore, NaHS root pretreatment resulted in induction of gene expression levels of an array of protective molecules, such as enzymatic antioxidants (cAPX, CAT, MnSOD, GR), heat shock proteins (HSP70, HSP80, HSP90) and aquaporins (PIP). Conclusion: Overall, we propose that H 2 S root pretreatment activates a coordinated network of heat shock defense-related pathways at a transcriptional level and systemically protects strawberry plants from heat shock-induced damage.

Plant, Cell & Environment, 2014

The interplay among polyamines (PAs) and reactive oxygen and nitrogen species (RNS and ROS) is em... more The interplay among polyamines (PAs) and reactive oxygen and nitrogen species (RNS and ROS) is emerging as a key issue in plant responses to salinity. To address this question, we analysed the impact of exogenous PAs [putrescine (Put), spermidine (Spd) and spermine (Spm)] on the oxidative and nitrosative status in citrus plants exposed to salinity. PAs partially reversed the NaCl-induced phenotypic and physiological disturbances. The expression of PA biosynthesis (ADC, SAMDC, SPDS and SPMS) and catabolism (DAO and PAO) genes was systematically up-regulated by PAs. In addition, PAs altered the oxidative status in salt-stressed plants as inferred by changes in ROS production and redox status accompanied by regulation of transcript expression and activities of various antioxidant enzymes. Furthermore, NaCl-induced up-regulation of NO-associated genes, such as NR, NADde, NOS-like and AOX, along with Snitrosoglutathione reductase and nitrate reductase activities, was partially restored by PAs. Protein carbonylation and tyrosine nitration are depressed by specific PAs whereas protein S-nitrosylation was elicited by all PAs. Furthermore, we identified 271 S-nitrosylated proteins that were commonly or preferentially targeted by salinity and individual PAs. This work helps improve our knowledge on the plant's response to environmental challenge.

Gene, 2014