Living mulch enhances soil enzyme activities, nitrogen pools and water retention in giant reed (Arundo donax L.) plantations.

Giant reed (Arundo donax L.) is one of the most well-studied perennial biomass crops because of its high productivity and potential to store carbon. Yet, little information on controlling weeds in giant reed plantations and their influences on the soil ecosystem is available. In the present study, three different weed control methods, i.e., intercropping (living mulch) with sweet clover (Melilotus officinalis L.), herbicide (glyphosate), and hoeing, were investigated in a 2-year giant reed farm. The intercropping presented significantly higher values (on average) of all the tested soil properties than herbicide and hoeing, except for the catalase activity and pH. The dehydrogenase, phosphatase, and urease activities in the soil under intercropping were higher than the herbicide by 75%, 65%, and 80% (on average), respectively. Also, the soil under intercropping had higher soil organic matter (SOM) and soil respiration than the herbicide by 20% and 25%, respectively. Intercropping also increased the content of N pools, i.e., NO3--N, NH4+-N, Org-N, and Total-N by 517%, 356%, 38%, and 137%, respectively, compared to herbicide. These findings illustrated that controlling weeds in biomass plantations through legume intercropping brings benefits not only to soil properties but also to biomass productivity.

Comparative study between the top six heavy metals involved in the EU RASFF notifications over the last 23 years.

From the Rapid Alert System for Food and Feed (RASFF) database, a total of 4728 notifications regarding the six most frequently notified heavy metals (i.e., arsenic, cadmium, lead, mercury, chromium, and nickel) were tracked from January 1, 2000, to December 31, 2022, and analyzed based on year, notification classification, notifying countries, countries of origin, product types, product categories, risk decision, and action taken. Human risk assessment owing to consumption of mercury- and cadmium-contaminated seafood was estimated as well. Results revealed that the highest numbers of notifications were on mercury (36.6%), cadmium (25.1%), and lead (14.1%). Interestingly, the number of total notifications was at its peak between 2011 and 2014; from 2015 onward, it started to decrease considerably. Alert, border rejection, and information notifications represented 29.6%, 21.9%, and 48.5% of the total notifications, respectively. Chromium and nickel resulted in 33.8% and 23.3% of border rejection notifications, respectively. About 52.0% of the alert notifications were on mercury. Serious notifications represented 34.9% of the total notifications. Mercury and cadmium notifications accounted for 54.9% and 25.8% of serious notifications, respectively. Italy was the most notifying country, recording the highest number of notifications on cadmium (29.0%), mercury (52.6%), chromium (81.0%), and nickel (78.7%). China was the most notified origin country with regards to arsenic (18.7%), cadmium (12.8%), lead (27.6%), chromium (71.2%), and nickel (66.9%) notifications. Notifications on food, food contact materials (FCM), and feed represented 71.9%, 23.4%, and 4.7%, respectively, of the total notifications. About 91.5% of mercury notifications were on fish and fish products; 24.3% of arsenic notifications related to fruits and vegetables; and 20.1% of cadmium notifications corresponded to cephalopods and products thereof. Notified products were largely withdrawn from the markets according to arsenic (20.3%), lead (17.9%), and mercury (18.0%) notifications and re-dispatched because of cadmium (20.5%), chromium (42.1%), and nickel (49.5%) notifications. The target hazard quotient (THQ) values for mercury in swordfish, sharks, and tuna and cadmium in squid were all also below the threshold value of 1, implying that there is no significant risk for consumers. Overall, media coverage of RASFF alerts and actions may raise awareness of heavy metal contamination among the general public and industry professionals. The primary dietary advice of our study is to stay away from species with high mercury contents. Also, identifying the most dangerous heavy metals (HMs) and the most polluting products can help researchers prioritize their efforts in finding sustainable solutions for them.

Green Biomass-Based Protein for Sustainable Feed and Food Supply: An Overview of Current and Future Prospective.

It is necessary to develop and deploy novel protein production to allow the establishment of a sustainable supply for both humans and animals, given the ongoing expansion of protein demand to meet the future needs of the increased world population and high living standards. In addition to plant seeds, green biomass from dedicated crops or green agricultural waste is also available as an alternative source to fulfill the protein and nutrient needs of humans and animals. The development of extraction and precipitation methods (such as microwave coagulation) for chloroplast and cytoplasmic proteins, which constitute the bulk of leaf protein, will allow the production of leaf protein concentrates (LPC) and protein isolates (LPI). Obtained LPC serves as a sustainable alternative source of animal-based protein besides being an important source of many vital phytochemicals, including vitamins and substances with nutritional and pharmacological effects. Along with it, the production of LPC, directly or indirectly, supports sustainability and circular economy concepts. However, the quantity and quality of LPC largely depend on several factors, including plant species, extraction and precipitation techniques, harvest time, and growing season. This paper provides an overview of the history of green biomass-derived protein from the early green fodder mill concept by Károly Ereky to the state-of-art of green-based protein utilization. It highlights potential approaches for enhancing LPC production, including dedicated plant species, associated extraction methods, selection of optimal technologies, and best combination approaches for improving leaf protein isolation.

Potassium Humate and Plant Growth-Promoting Microbes Jointly Mitigate Water Deficit Stress in Soybean Cultivated in Salt-Affected Soil.

Lack of high-quality irrigation water and soil salinity are two main environmental factors that affect plant development. When both stressors are combined, the soil becomes sterile and constrains plant productivity. Consequently, two field trials were designed to assess whether plant growth-promoting microbes (PGPMs; Bradyrhizobium japonicum (USDA 110) and Trichoderma harzianum) and potassium humate (K-humate) can stimulate soybean growth, productivity, and seed quality under two different watering regimes as follows: (i) well-watered (WW), where plants were irrigated at 12-day intervals (recommended), and (ii) water stress (WS), where plants were irrigated at the 18-day intervals in salt-affected soil during 2020 and 2021 seasons. Results revealed that coupled application of PGPMs and K-humate resulted in a substantial improvement in K+ levels in the leaves compared to Na+ levels, which has a direct positive impact on an enhancement in the antioxidants defense system (CAT, POX, SOD), which caused the decline of the oxidative stress indicators (H2O2, MDA, and EL%) as well as proline content under water stress in salt-affected soil. Hence, a significant increase in root length, nodule weight, soybean relative water content (RWC), stomatal conductance, photosynthetic pigments, net photosynthetic rate, soluble protein, seed carbohydrate content as well as the number of pods plant-1 and seed yield was reported. In conclusion, the combined application of PGPMs and K-humate might be recommended to maximize the soybean growth and productivity under harsh growth conditions (e.g., water stress and soil salinity).

Bioactive metabolite profile and antioxidant properties of brown juice, a processed alfalfa (Medicago sativa) by-product.

Recently, leaf protein concentrate (LPC) has gained increased attention in response to the constantly growing protein demand. Green biorefineries can become more economical by valorizing their by-products and reducing environmental risks. The current study describes the variations in the antioxidant capacity and phytochemical composition of a liquid by-product (referred to as brown juice (BJ)) obtained during the extraction of leaf protein concentrate (LPC) from the fresh biomass of alfalfa (Medicago sativa L.). Four varieties of alfalfa were investigated during three harvest times, i.e., August 2017 (first harvest), September 2017 (second harvest), and June 2018 (third harvest). Also, the fresh BJ was lacto-fermented to extend its preservation period but also modifying its composition. The results of different general phytochemical composition analyses and antioxidant assays revealed similar tendencies across different alfalfa varieties and harvest times. Most of the phytochemicals in the BJ identified by HPLC-MS/MS can be classified as flavonoids/flavonoid derivatives, e.g., apigenin, naringenin, luteolin, formononetin. Substantially, the lacto-fermentation process induced a switch into aglycones, e.g., apigenin content increased by an order of magnitude, while apigenin-7-O-glucuronide content was halved after lacto-fermentation. Additionally, several B vitamins were detected, including B2, B3, and B7. These results could provide a basis for various ways of industrial valorization but need to be strengthened by data generated from large-scale production.

Comparison of Wet Fractionation Methods for Processing Broccoli Agricultural Wastes and Evaluation of the Nutri-Chemical Values of Obtained Products.

The main objective of this study was to increase the economic value of broccoli green agro-waste using three wet fractionation methods in the shadow of green biorefinery and the circular economy. Product candidates were obtained directly by using a mechanical press, and indirectly by using microwave coagulation or via lactic acid fermentation of green juice. The leaf protein concentrates (LPC) fractions displayed significantly higher dry matter content and crude protein content (34-39 m/m% on average) than the green juice fraction (27.4 m/m% on average), without considerable changes in the amino acids composition ratio. UHPLC-ESI-ORBITRAP-MS/MS analysis showed that kaemferol and quercetin are the most abundant flavonols, forming complexes with glycosides and hydroxycinnamic acids in green juice. Lacto-ermentation induced a considerable increase in the quantity of quercetin (48.75 µg·g-1 dry weight) and kaempferol aglycons (895.26 µg·g-1 dry weight) of LPC. In contrast, chlorogenic acid isomers and sulforaphane disappeared from LPC after lactic acid fermentation, while microwave treatment did not cause significant differences. These results confirm that both microwave treatment and lacto-fermentation coagulate and concentrate most of the soluble proteins. Also, these two processes affect the amount of valuable phytochemicals differently, so it should be considered when setting the goals.

Application of Silica Nanoparticles in Combination with Two Bacterial Strains Improves the Growth, Antioxidant Capacity and Production of Barley Irrigated with Saline Water in Salt-Affected Soil.

Exploitation of low-quality water or irrigation of field crops with saline water in salt-affected soil is a critical worldwide challenge that rigorously influences agricultural productivity and sustainability, especially in arid and semiarid zones with limited freshwater resources. Therefore, we investigated a synergistic amendment strategy for salt-affected soil using a singular and combined application of plant growth-promoting rhizobacteria (PGPR at 950 g ha-1; Azotobacter chroococcum SARS 10 and Pseudomonas koreensis MG209738) and silica nanoparticles (SiNPs) at 500 mg L-1 to mitigate the detrimental impacts of irrigation with saline water on the growth, physiology, and productivity of barley (Hordum vulgare L.), along with soil attributes and nutrient uptake during 2019/2020 and 2020/2021. Our field trials showed that the combined application of PGPR and SiNPs significantly improved the soil physicochemical properties, mainly by reducing the soil exchangeable sodium percentage. Additionally, it considerably enhanced the microbiological counts (i.e., bacteria, azotobacter, and bacillus) and soil enzyme activity (i.e., urease and dehydrogenase) in both growing seasons compared with the control. The combined application of PGPR and SiNPs alleviated the detrimental impacts of saline water on barley plants grown in salt-affected soil compared to the single application of PGPR or SiNPs. The marked improvement was due to the combined application of PGPR and SiNPs, which enhanced the physiological properties (e.g., relative chlorophyll content (SPAD), relative water content (RWC), stomatal conductance, and K/Na ratio), enzyme activity (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX)), and yield and yield-related traits and nutrient uptake (N, P, and K) of barley plants. Moreover, the Na+ content, hydrogen peroxide (H2O2) content, lipid peroxidation (MDA), electrolyte leakage (EL), and proline content were reduced upon the application of PGPR + SiNPs. These results could be important information for cultivating barley and other cereal crops in salt-affected soil under irrigation with saline water.

Quinoa Response to Application of Phosphogypsum and Plant Growth-Promoting Rhizobacteria under Water Stress Associated with Salt-Affected Soil.

The aim of the study was to estimate the impact of soil amendments (i.e., phosphogypsum and plant growth-promoting rhizobacteria (PGPR)) separately or their combination on exchangeable sodium percentage (ESP), soil enzymes' activity (urease and dehydrogenase), pigment content, relative water content (RWC), antioxidant enzymatic activity, oxidative stress, productivity, and quality of quinoa under deficient irrigation conditions in two field experiments during the 2019-2020 and 2020-2021 seasons under salt-affected soil. Results revealed that ESP, soil urease activity, soil dehydrogenase activity, leaf chlorophyll a, b, and carotenoids, leaf K content, RWC, SOD (superoxide dismutase), CAT (catalase), and POD (peroxidase) activities were declined, resulting in overproduction of leaf Na content, proline content, and oxidative stress indicators (H2O2, malondialdehyde (MDA) and electrolyte leakage) under water stress and soil salinity, which negatively influence yield-related traits, productivity, and seed quality of quinoa. However, amendment of salt-affected soil with combined phosphogypsum and seed inoculation with PGPR under deficient irrigation conditions was more effective than singular application and control plots in ameliorating the harmful effects of water stress and soil salinity. Additionally, combined application limited Na uptake in leaves and increased K uptake and leaf chlorophyll a, b, and carotenoids as well as improved SOD, CAT, and POD activities to ameliorate oxidative stress indicators (H2O2, MDA, and electrolyte leakage), which eventually positively reflected on productivity and quality in quinoa. We conclude that the potential utilization of phosphogypsum and PGPR are very promising as sustainable eco-friendly strategies to improve quinoa tolerance to water stress under soil salinity.

The Integrated Amendment of Sodic-Saline Soils Using Biochar and Plant Growth-Promoting Rhizobacteria Enhances Maize (Zea mays L.) Resilience to Water Salinity.

The utilization of low-quality water or slightly saline water in sodic-saline soil is a major global conundrum that severely impacts agricultural productivity and sustainability, particularly in arid and semiarid regions with limited freshwater resources. Herein, we proposed an integrated amendment strategy for sodic-saline soil using biochar and/or plant growth-promoting rhizobacteria (PGPR; Azotobacter chroococcum SARS 10 and Pseudomonas koreensis MG209738) to alleviate the adverse impacts of saline water on the growth, physiology, and productivity of maize (Zea mays L.), as well as the soil properties and nutrient uptake during two successive seasons (2018 and 2019). Our field experiments revealed that the combined application of PGPR and biochar (PGPR + biochar) significantly improved the soil ecosystem and physicochemical properties and K+, Ca2+, and Mg2+ contents but reduced the soil exchangeable sodium percentage and Na+ content. Likewise, it significantly increased the activity of soil urease (158.14 ± 2.37 and 165.51 ± 3.05 mg NH4+ g-1 dry soil d-1) and dehydrogenase (117.89 ± 1.86 and 121.44 ± 1.00 mg TPF g-1 dry soil d-1) in 2018 and 2019, respectively, upon irrigation with saline water compared with non-treated control. PGPR + biochar supplementation mitigated the hazardous impacts of saline water on maize plants grown in sodic-saline soil better than biochar or PGPR individually (PGPR + biochar > biochar > PGPR). The highest values of leaf area index, total chlorophyll, carotenoids, total soluble sugar (TSS), relative water content, K+ and K+/Na+ of maize plants corresponded to PGPR + biochar treatment. These findings could be guidelines for cultivating not only maize but other cereal crops particularly in salt-affected soil and sodic-saline soil.

Uptake Dynamics of Ionic and Elemental Selenium Forms and Their Metabolism in Multiple-Harvested Alfalfa (Medicago sativa L.).

A pot experiment, under greenhouse conditions, was carried out aiming at investigating the agronomic biofortification of alfalfa (Medicago sativa L.) with Se and monitoring the Se uptake and accumulation dynamics within four consecutive harvests within the same growing season. Two ionic Se forms, i.e., sodium selenate (Se (VI)) and sodium selenite (Se (IV)), were applied once at a rate of 1, 10, and 50 mg kg-1 (added on Se basis), while 10 and 50 mg L-1 of a red elemental Se (red Se0) were used; all Se treatments were added as soil application. Application of Se (VI) at the rate of 50 mg kg-1 was toxic to alfalfa plants. The effect of Se forms on Se accumulation in alfalfa tissues, regardless of the applied Se concentration, follows: Se (VI) > Se (IV) > red Se0. The leaf, in general, possessed higher total Se content than the stem in all the treatments. The accumulation of Se in stem and leaf tissues showed a gradual decline between the harvests, especially for plants treated with either Se (VI) or Se (IV); however, the chemically synthesized red Se0 showed different results. The treatment of 10 mg kg-1 Se (VI) resulted in the highest total Se content in stem (202.5 and 98.0 µg g-1) and leaf (643.4 and 284.5 µg g-1) in the 1st and 2nd harvests, respectively. Similar tendency is reported for the Se (IV)-treated plants. Otherwise, the application of red Se0 resulted in a lower Se uptake; however, less fluctuation in total Se content between the four harvests was noticed compared to the ionic Se forms. The Se forms in stem and leaf of alfalfa extracted by water and subsequently by protease XIV enzyme were measured by strong anion exchange (SAX) HPLC-ICP-MS. The major Se forms in our samples were selenomethionine (SeMet) and Se (VI), while neither selenocysteine (SeCys) nor Se (IV) was detected. In water extract, however, Se (VI) was the major Se form, while SeMet was the predominant form in the enzyme extract. Yet, Se (VI) and SeMet contents declined within the harvests, except in stem of plants treated with 50 mg L-1 red Se0. The highest stem or leaf SeMet yield %, in all harvests, corresponded to the treatment of 50 mg L-1 red Se0. For instance, 63.6% (in stem) and 38.0% (in leaf) were calculated for SeMet yield % in the 4th harvest of plants treated with 50 mg L-1 red Se0. Our results provide information about uptake and accumulation dynamics of different ionic Se forms in case of multiple-harvested alfalfa, which, besides being a good model plant, is an important target plant species in green biorefining.

Raw and Fermented Alfalfa Brown Juice Induces Changes in the Germination and Development of French Marigold (Tagetes patula L.) Plants.

Organic and ecological farming programs require new and efficient biostimulants with beneficial properties for the sustainable and safe production of seedlings and ornamental plants. We examined the effect of non-fermented and lacto-fermented alfalfa brown juice (BJ) on seed germination and the vegetative, physiological, and anatomical properties of French marigold (Tagetes patula L. 'Csemo') plants which were treated with 0.5-10% fermented and non-fermented BJ, with tap water applied as a control. Applying 0.5% fermented BJ significantly improved seed germination compared with non-fermented BJ, resulting in an increase of 9.6, 11.2, 10.9, and 41.7% in the final germination percent, germination rate index, germination index, and vigor index, respectively. In addition, it increased the root and shoot length by 7.9 and 16.1%, respectively, root and shoot dry mass by 20 and 47.6%, respectively, and the number of leaves by 28.8% compared to the control. Furthermore, an increase in contents of water-soluble phenol, chlorophyll a and b, and carotenoid was reported upon the application of 0.5% fermented BJ, while peroxidase activity decreased. Our results prove that alfalfa BJ can be enrolled as a biostimulant as part of the circular farming approach which supports the sustainable horticultural practice.

Identification of Bioactive Phytochemicals in Leaf Protein Concentrate of Jerusalem Artichoke (Helianthus tuberosus L.).

Jerusalem artichoke (JA) is widely known to have inulin-rich tubers. However, its fresh aerial biomass produces significant levels of leaf protein and economic bioactive phytochemicals. We have characterized leaf protein concentrate (JAPC) isolated from green biomass of three Jerusalem artichoke clones, Alba, Fuseau, and Kalevala, and its nutritional value for the human diet or animal feeding. The JAPC yield varied from 28.6 to 31.2 g DM kg-1 green biomass with an average total protein content of 33.3% on a dry mass basis. The qualitative analysis of the phytochemical composition of JAPC was performed by ultra-high performance liquid chromatography-electrospray ionization-Orbitrap/mass spectrometry analysis (UHPLC-ESI-ORBITRAP-MS/MS). Fifty-three phytochemicals were successfully identified in JAPC. In addition to the phenolic acids (especially mono- and di-hydroxycinnamic acid esters of quinic acids) several medically important hydroxylated methoxyflavones, i.e., dimethoxy-tetrahydroxyflavone, dihydroxy-methoxyflavone, hymenoxin, and nevadensin, were detected in the JAPC for the first time. Liquiritigenin, an estrogenic-like flavanone, was measured in the JAPC as well as butein and kukulkanin B, as chalcones. The results also showed high contents of the essential amino acids and polyunsaturated fatty acids (PUFAs; 66-68%) in JAPC. Linolenic acid represented 39-43% of the total lipid content; moreover, the ratio between ω-6 and ω-3 fatty acids in the JAPC was ~0.6:1. Comparing the JA clones, no major differences in phytochemicals, fatty acid, or amino acid compositions were observed. This paper confirms the economic and nutritional value of JAPC as it is not only an alternative plant protein source but also as a good source of biological valuable phytochemicals.

Would fertilization history render the soil microbial communities and their activities more resistant to rainfall fluctuations?

Water stress and nutrient supply are two of the most ubiquitous global changes that surely drive substantial variations not only in agricultural productivity but also extend to alert soil living organisms. The present study aims to understand the intrinsic changes in the composition of soil populations and their functions due to the interaction between long-term fertilization and rainfall fluctuations, seeing whether fertilization history would render the soil microbial communities and their activities more resistant to water stress or not. The experiment was established in 1988 on a typical meadow soil (Vertisols) as a rainfed maize monoculture receiving six elevated rates of NPK annually. The 30-year average annual precipitation of the growing season in this region is 345.1 mm. However, in 2010 rainfall was 106.1% greater than the average, while in 2011 it was 26.5% lower. The results show that long-term NPK fertilization has made the soil microbes more tolerant to changes in soil moisture content resulting from rainfall fluctuations. Soil microbes and their activities, however, did not follow a dose-response relationship of NPK as soil moisture content was the main driving factor. Numbers of total fungi, cellulose decomposing bacteria, and nitrifying bacteria increased as rainfall in 2010 increased. Moreover, microbial biomass carbon in 2010 was almost 2-fold higher than in 2009. Soil respiration in 2010 was 11 and 35% higher than in 2009 and 2011, respectively. Otherwise, high rainfall in 2010 significantly diminished soil NO3- content and nitrification rate. Soil enzyme activity showed a higher response to soil moisture than the rate of NPK. The highest activity of phosphatase, dehydrogenase, and saccharase was measured in the driest year (2011), while urease displayed its highest activity in 2010. High rates of NPK significantly reduced soil dehydrogenase activity. These results illustrate how important it is for fertilizer programs to be flexible to match expected climate change in order to improve productivity and reduce environmental pollution.

Application of magnetic field improves growth, yield and fruit quality of tomato irrigated alternatively by fresh and agricultural drainage water.

Although the North Delta region in Egypt is one of the most densely populated areas in the world, it suffers from a severe shortage of fresh water needed to irrigate crops. So usually farmers resort to the use of low-quality water, such as agricultural drainage water, which could pose a threat to the quality of crops and then human health. Two field experiments were carried out during two consecutive summer seasons of 2014 and 2015 aimed at delivering more information about the pros and cons of alternative irrigation for tomato using fresh and agricultural drainage water with or without applying of magnetic field. The twelve surface irrigations, which tomato needs during its whole growing season, were applied alternatively between fresh and agricultural drainage water, respectively, at the following percentages (100 + 0), (75 + 25), (50 + 50), (25 + 75) and (0 + 100). Magnetic field was applied using iron fillings at a rate of 150 kg ha-1. The results revealed that growth parameters, early, total and relative yield, marketable yield and total chlorophyll and NPK content of leaves were gradually decreased with increasing the irrigation using agricultural drainage water. However, irrigating tomato by 100% fresh water had the highest values, while using of 100% agricultural drainage water displayed the lowest values. Contrarily, vitamin C, total soluble solids (TSS) and fruit firmness where at their highest values when tomato irrigated by 100% of agricultural drainage water. Applying of magnetic field not only enhances the growth, yield and quality of tomato under irrigation using agricultural water but also under fresh water. These results are of importance in areas where the use of agricultural drainage water irrigating crops is inevitable for enhancing yield and its quality and consequently ensuring food safety.

Biochemical traits of Bacillus subtilis MF497446: Its implications on the development of cowpea under cadmium stress and ensuring food safety.

The present study aimed at assessment of different application methods of Bacillus subtilis MF497446 to induce development of cowpea ensuring food safety under cadmium (Cd) stress. Also, isolation, plant growth promoting (PGP) traits and 16 S rRNA-based identification of Bacillus subtilis MF497446 is documented. Out of 24 Bacillus isolates (AS1-AS24), only four isolates (AS4, AS12, AS14 and AS22) showed greater Cd tolerance up to 18 mg L-1. The greatest PGP traits under Cd stress were displayed by Bacillus isolate (AS12); which, also, enhanced seedling elongation and vigor index of cowpea under Cd stress. Phylogenetic analysis, based on 16 S rRNA, confirmed that this promising Bacillus isolate (AS12) belongs to Bacillus subtilis and is referred to as B. subtilis MF497446. Treatment of inoculation+soaking for 90 min of cowpea seeds by B. subtilis MF497446 resulted in the best development of cowpea plants under Cd stress (up to 9 mg kg-1); as fresh and dry masses of cowpea increased from 6.80 to 1.54 to 12.35 and 2.59 g plant-1, respectively. Moreover, shoot and root lengths were 19.66 and 28.33 cm when cowpea seeds were treated by B. subtilis MF497446 (inoculation+soaking for 90 min) compared to 11.33 and 10.66 cm, respectively, for control (Cd stress only). Application of B. subtilis MF497446 (as inoculation+soaking for 90 min) reduced Cd accumulation and bioconcentration factor in cowpea plants by 29.2 and 28.9%, respectively, compared to control (Cd stress only). These results clearly reveal that applying of B. subtilis MF497446 to crops grown on Cd-contaminated soil enhances plant growth and eliminates (or at least diminishes) the risks to human health ensuring food safety.

Silica nanoparticles boost growth and productivity of cucumber under water deficit and salinity stresses by balancing nutrients uptake.

The role of amorphous silica nanoparticles (SiNPs) in enhancing growth and yield of cucumber under water deficit and salinity stresses was assessed. A field experiment under greenhouse conditions was established using 4 different levels of SiNPs (100, 200, 300 and 400 mg kg-1) and 3 different watering regimes calculated based on crop evapotranspiration (ETc) (100, 85 and 70% of ETc). Electrical conductivity and sodium adsorption ratio of irrigation water were 1.7 dS m-1 and 4.63 respectively. The results revealed that SiNPs improved growth and productivity of cucumber regardless of quantity of supplied water; however, the greatest increase corresponded to irrigating cucumber at the rate of 85% of ETc. Applying SiNPs at rate of 200 mg kg-1 showed the greatest increase specially when cucumber plants received 85% of their ETc causing an increase of 20, 51 and 156% in plant height, chlorophyll and fruit yield, respectively, compared to untreated plants. These increases could be due to alerting nutrient uptake as SiNPs clearly increased contents of nitrogen (by 30%), potassium (by 52, 75 and 41% in root, stem and leaf, respectively) and silicon (by 51, 57, 8 and 78% in root, stem, leaf and fruit, respectively). Otherwise, same treatment reduced sodium uptake by 38, 77 and 38% in root, stem and leaf, respectively; consequently, potassium-sodium ratio increased by 149, 735 and 127% in root, stem and leaf, respectively. The significant role of SiNPs in mitigating water deficit and salinity stresses could be referred to high silicon content found in leaf which regulates water losses via transpiration. Also, high K+ content found in roots of cucumber helps plants to tolerate abiotic stresses as a result of maintaining ion homeostasis and regulating the osmotic balance as well as controlling stomatal opening which helps plants to adapt to salinity and water deficit stresses.

Selenate tolerance and selenium hyperaccumulation in the monocot giant reed (Arundo donax), a biomass crop plant with phytoremediation potential.

The response of giant reed (Arundo donax L.) to selenium (Se), added as selenate, was studied. The development, stress response, uptake, translocation, and accumulation of Se were documented in three giant reed ecotypes STM (Hungary), BL (USA), and ESP (Spain), representing different climatic zones. Plantlets regenerated from sterile tissue cultures were grown under greenhouse conditions in sand supplemented with 0, 2.5, 5, and 10 mg Se kg-1 added as sodium selenate. Total Se content was measured in different plant parts using hydride generation atomic fluorescence spectroscopy. All plants developed normally in the 0-5.0 mg Se kg-1 concentration range regardless of ecotype, but no growth occurred at 10.0 mg Se kg-1. There were no signs of chlorosis or necrosis, and the photosynthetic machinery was not affected as evidenced by no marked differences in the structure of thylakoid membranes. There was no change in the maximum quantum yield of photosystem II (Fv/Fm ratio) in the three ecotypes under Se stress, except for a significant negative effect in the ESP ecotype in the 5.0 mg Se kg-1 treatment. Glutathione peroxidase (GPx) activity increased as the Se concentration increased in the growth medium. GPx activity was higher in the shoot system than the root system in all Se treatments. All ecotypes showed great capacity of take up, translocate and accumulate selenium in their stem and leaf. Relative Se accumulation is best described as leaf ˃˃ stem ˃ root. The ESP ecotype accumulated 1783 µg g-1 in leaf, followed by BL with 1769 µg g-1, and STM with 1606 µg g-1 in the 5.0 mg Se kg-1 treatment. All ecotypes showed high values of translocation and bioaccumulation factors, particularly the ESP ecotype (10.1 and 689, respectively, at the highest tolerated Se supplementation level). Based on these findings, Arundo donax has been identified as the first monocot hyperaccumulator of selenium, because Se concentration in the leaves of all three ecotypes, and also in the stem of the ESP ecotype, is higher than 0.1% (dry weight basis) under the conditions tested. Tolerance up to 5.0 mg Se kg-1 and the Se hyperaccumulation capacity make giant reed a promising tool for Se phytoremediation.

Effect of some osmoregulators on photosynthesis, lipid peroxidation, antioxidative capacity, and productivity of barley (Hordeum vulgare L.) under water deficit stress.

Water deficit stress is an abiotic stress that causes reductions in growth and yield of many field crops around the world. The present research was aimed to elucidate the mitigating efficiency of exogenous application of select osmoregulators and biostimulants, i.e., potassium dihydrogen phosphate, actosol® (humic acid), Amino more (amino acids), and Compound fertilizer, applied as a spray that reached both foliage and the soil, on growth characteristics, antioxidant capacity, and productivity of barley (Hordeum vulgare L. Giza123) under water deficit stress during two successive growing seasons of field experiments in Egypt. Water deficit resulted in stress as estimated by stress indicators and decreased growth and poor health and development as reflected in statistically significant decreases in chlorophyll a and b and major nutrient (NPK) levels in tissues, stem length, number of leaves, and fresh and dry mass as well as yield components such as spike length, grains per spike, biological yield, grain yield, and 1000-grain weight. As a response to water deficit stress, reactive oxygen species (ROS, i.e., superoxide and hydrogen peroxide) levels increased significantly resulting in lipid peroxidation and decreased membrane integrity and significant increases in antioxidant enzymes such as catalase (CAT), polyphenol oxidase (PPO), and peroxidase (POX). All four treatments alleviated the detrimental impacts of water deficit stress as evidenced by statistically significantly increased photosynthetic pigment concentration, tissue NPK levels, growth, and yield parameters compared to the water deficit-stressed control, while the stress responses were significantly reduced. The osmoregulators used either partially restored the growth and yield of osmotic-stressed barley plants or certain treatments enhanced them. All osmoregulators tested mitigated the adverse impacts of water deficit stress on barley plants, but the highest induction was found when plants were treated with actosol®. The beneficial effects of the osmoregulators tested were the strongest overall in the order actosol® ˃ potassium dihydrogen phosphate ˃ Amino more ˃ Compound fertilizer.

Uptake of nicotine from discarded cigarette butts - A so far unconsidered path of contamination of plant-derived commodities.

This study aimed to elucidate the origin of the widespread nicotine contamination of plant-derived commodities, by conducting field experiments with various herbs and spice plants. By scattering tobacco and cigarette butts on the field and subsequent nicotine analyses of the acceptor plants, we verified that the alkaloid is leached out into the soil and is taken up by the crop plants. This path of contamination pertains even when there is only one cigarette butt per square meter. Even such minor pollution results - at least in the case of basil and peppermint - in considerable high nicotine contaminations, which exceed the maximum residue level by more than 20-fold. The data reported here clearly outline the large practical relevance of this soil-borne contamination path and imply that unthoughtful disposal of cigarette butts in the field by farm workers may be the reason for the widespread occurrence of nicotine contamination in plant-derived commodities. Therefore, such misbehavior needs to be prevented using education and sensitization, and by including this issue into the guidelines of good agricultural practice.

Exogenous nanosilica improves germination and growth of cucumber by maintaining K+/Na+ ratio under elevated Na+ stress.

The current work was aimed to elucidate the role of engineered nanosilica (SiNPs) particles to mitigate the damaging impacts of Na+-derived salinity on cucumber (Cucumis sativus) Beit Alpha variety by conducting in vitro experiments applying various Na+ concentrations i.e. 0, 1000, 2000, 3000, 4000 and 5000 mg L-1. By treating seeds and seedlings, respectively, of cucumber with SiNPs (0, 100, 200 and 300 ppm) and subsequent determination some germination and vegetative parameters as well as chemical analysis of seedlings, we verified that SiNPs succeeded to alleviate the detrimental effects of high Na+ salinity by increasing germination parameters and vegetative growth of cucumber seedlings. Even as little as 100 ppm of N-Si results in considerable improvement of seed germination and seedlings growth of cucumber compared to the control, while 200 ppm was optimal among the doses tested. At 5000 mg Na+ L-1, applying SiNPs with 200 ppm increased final germination percentage by 101% over control, vigor index by 101%, germination rate index by 116%, germination index by 110%, fresh mass by 13%, K+/Na+ ratio by 77%, shoot dry mass by 384%, root dry mass by 304% and plant height by 70%. The results mentioned in this paper obviously outline the large practical relevance of SiNPs and imply that applying of SiNPs for cucumber seeds and seedlings under high Na+-derived salinity enhances germination and growth as a result for decreasing Na+ uptake and sequentially improves high K+/Na+ ratio.