Publications by authors named "Manzer H Siddiqui"

56 Publications

Correction: Seed germination ecology of Conyza stricta Willd. and implications for management.

PLoS One 2021 26;16(2):e0248083. Epub 2021 Feb 26.

[This corrects the article DOI: 10.1371/journal.pone.0244059.].
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0248083PLOS
February 2021

Exogenous Hydrogen Sulfide Alleviate Copper Stress Impacts in Artemisia annua L.: Growth, Antioxidant Metabolism, Glandular Trichomes Development and Artemisinin Biosynthesis.

Plant Biol (Stuttg) 2021 Feb 3. Epub 2021 Feb 3.

Department of Botany, Aligarh Muslim University, Aligarh, 202 002, India.

Essential micronutrients for plants (some of which are metals) are necessary to regulate many routine processes in plants, their excess, however, can have detrimental consequences and can hamper the plant growth, physiology, and metabolism. In this investigation, the physio-biochemical mechanisms involved in exogenous hydrogen sulfide-mediated (H S) alleviation of copper (Cu) stress in Artemisia annua were assessed. The two different levels of Cu (20, 40 mg kg ), one H S treatment (200 µM) and their combinations were introduced into the soil, while one set of plants was kept as control. Results suggested that presence of Cu in the soil reduced growth and biomass, photosynthetic parameters, chlorophyll content and fluorescence, gas exchange parameters and induced antioxidant enzyme activities. Copper stress enhanced the production of TBARS content and increased Cu content in root and shoot tissues of affected plants. Exogenous application of H S enhanced the physio-biochemical characteristics of Cu-treated A. annua plants. Hydrogen sulfide reduced the lipid peroxidation by enhancing the activity of antioxidant enzymes in Cu-stressed plants as compared with their respective controls. Hydrogen sulfide also reduced the Cu content in different parts of the plant, whereas increased the photosynthetic efficiency, trichome density, average area of trichomes and artemisinin content. Therefore, our result provides a comprehension into the defensive role of H S in Cu-stressed A. annua plants.
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http://dx.doi.org/10.1111/plb.13242DOI Listing
February 2021

Application of soil biofertilizers to a clayey soil contaminated with Sclerotium rolfsii can promote production, protection and nutritive status of Phaseolus vulgaris.

Chemosphere 2020 Dec 17;271:129321. Epub 2020 Dec 17.

Soils and Water Department, Faculty of Agriculture, Benha University, Egypt. Electronic address:

Sclerotium rolfsii is a soil-borne fungus that causes big losses in productivity of various plant species including Phaseolus vulgaris L. The objectives of this study were to (1) evaluate the impacts of Sclerotium rolfsii on growth and production of common bean plants, (2) determine the effects of Sclerotium rolfsii on nutritive contents of beans, and (3) test the efficacy of bio-inoculants on suppressing plant infection with Sclerotium rolfsii. To fulfill these objectives, we used a coupled pot and field experimental approaches during two growing seasons. Common beans were inoculated with either arbuscular mycorrhizal fungi (Claroideoglomus etunicatum), Saccharomyces cerevisiae, or Trichoderma viride solely or in different combinations. Non-inoculated plants and fungicide treated ones were considered as reference treatments. Throughout these experiments, minimal amounts of rock phosphate were added during soil preparation for bio-inoculated treatments, while the non-inoculated reference treatments received a full dose of P as calcium superphosphate. Results revealed that all tested bioinoculants significantly raised the activities of plant defense enzymes i.e. chitinase, peroxidase and polyphenoloxidase as compared to non-inoculated control. Likewise, pre-, post- and plant survival percentages significantly increased due to these bio-inoculations. Increased survival percentages were attributed to the concurrent increases in uptake of N, P and Zn nutrients by plants treated with bioinoculants. In this concern, plant nutrients uptake was higher in combined than single bio-inoculant treatments. Moreover, the uptake values of plant nutrients owing to the combined bio-inoculants were higher than the corresponding ones achieved due to fungicide treatment. In conclusion, application of the tested bio-inoculants, especially the combined ones can be considered an eco-friendly approach that not only enhances plants resistance against infection with Sclerotium rolfsii but also improves plant nutritive status.
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http://dx.doi.org/10.1016/j.chemosphere.2020.129321DOI Listing
December 2020

Calcium-hydrogen sulfide crosstalk during K-deficient NaCl stress operates through regulation of Na/H antiport and antioxidative defense system in mung bean roots.

Plant Physiol Biochem 2021 Feb 8;159:211-225. Epub 2020 Dec 8.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 2455, Saudi Arabia.

Present investigation reports the role of calcium (Ca) and hydrogen sulfide (HS) crosstalk associated with Vigna radiata seedlings subjected to K deficient conditions under short-term (24 h) and long-term (72 h) NaCl stress. Perusal of the data reveals that under short-term NaCl stress an initial decline in K level led to the elevation in Ca and HS levels along with improvement in antioxidant system and reduction in reactive oxygen species (ROS) production. Under long-term NaCl stress a further decline in K content was deleterious that led to a lower K/Na ratio. This was followed by reduction in antioxidant system along with excessive accumulation of ROS and methylglyoxal content, and increased membrane damage. However, supplementation of the seedling roots with Ca enhanced biosynthesis of HS through enhancing cysteine pool. The present findings suggest that synergistic action of Ca and HS induced the activity of H-ATPase that created H gradient which in turn induced Na/H antiport system that accelerated K influx and Na efflux. All of these together contributed to a higher K/Na ratio, activation of antioxidative defense system, and maintenance of redox homeostasis and membrane integrity in Ca-supplemented stressed seedlings. Role of Ca and HS in the regulation of Na/H antiport system was validated by the use of sodium orthovanadate (plasma membrane H-ATPase inhibitor), tetraethylammonium chloride (K channel blocker), and amiloride (Na/H antiporter inhibitor). Application of Ca-chelator EGTA (ethylene glycol-bis(b-aminoethylether)-N,N,N',N'-tetraacetic acid) and HS scavenger hypotaurine abolished the effect of Ca, suggesting the involvement of Ca and HS in the alleviation of NaCl stress. Moreover, use of EGTA and HT also substantiates the downstream functioning of HS during Ca-mediated regulation of plant adaptive responses to NaCl stress. To sum up, present findings reveal the association of Ca and HS signaling in the regulation of ion homeostasis and antioxidant defense during K-deficient NaCl stress.
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http://dx.doi.org/10.1016/j.plaphy.2020.11.055DOI Listing
February 2021

Seed germination ecology of Conyza stricta Willd. and implications for management.

PLoS One 2020 29;15(12):e0244059. Epub 2020 Dec 29.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia.

Numerous cropping systems of the world are experiencing the emergence of new weed species in response to conservation agriculture. Conyza stricta Willd. is being a newly emerging weed of barley-based cropping systems in response to conservational tillage practices. Seed germination ecology of four populations (irrigated, rainfed, abandoned and ruderal habitats) was studied in laboratory and greenhouse experiments. The presence/absence of seed dormancy was inferred first, which indicated seeds were non-dormant. Seed germination was then recorded under various photoperiods, constant and alternating day/night temperatures, and pH, salinity and osmotic potential levels. Seedling emergence was observed from various seed burial depths. Seeds of all populations proved photoblastic and required 12-hour light/dark period for germination. Seeds of all populations germinated under 5-30°C constant temperature; however, peak germination was recorded under 17.22-18.11°C. Nonetheless, the highest germination was noted under 20/15°C alternating day/night temperature. Ruderal and irrigated populations better tolerated salinity and germinated under 0-500 mM salinity. Similarly, rainfed population proved more tolerant to osmotic potential than other populations. Seeds of all populations required neutral pH for the highest germination, whereas decline was noted in germination under basic and alkaline pH. Seedling emergence was retarded for seeds buried >2 cm depth and no emergence was recorded from >4 cm depth. These results add valuable information towards our understanding of seed germination ecology of C. stricta. Seed germination ability of different populations under diverse environmental conditions suspects that the species can present severe challenges in future if not managed. Deep seed burial along with effective management of the emerging seedlings seems a pragmatic option to manage the species in cultivated fields. However, immediate management strategies are needed for rest of the habitats.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0244059PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7771675PMC
February 2021

Mitigation of Nickel Toxicity and Growth Promotion in Sesame through the Application of a Bacterial Endophyte and Zeolite in Nickel Contaminated Soil.

Int J Environ Res Public Health 2020 11 28;17(23). Epub 2020 Nov 28.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.

Nickel (Ni) bioavailable fraction in the soil is of utmost importance because of its involvement in plant growth and environmental feedbacks. High concentrations of Ni in the soil environment, especially in the root zone, may retard plant growth that ultimately results in reduced plant biomass and yield. However, endophytic microorganisms have great potential to reduce the toxicity of Ni, especially when applied together with zeolite. The present research work was conducted to evaluate the potential effects of an endophytic bacterium sp. MN13 in combination with zeolite on the physiology, growth, quality, and yield of sesame plant under normal and Ni stressed soil conditions through possible reduction of Ni uptake. Surface sterilized sesame seeds were sown in pots filled with artificially Ni contaminated soil amended with zeolite. Results revealed that plant agronomic attributes such as shoot root dry weight, total number of pods, and 1000-grains weight were increased by 41, 45, 54, and 65%, respectively, over control treatment, with combined application of bacteria and zeolite in Ni contaminated soil. In comparison to control, the gaseous exchange parameters (CO assimilation rate, transpiration rate, stomatal- sub-stomatal conductance, chlorophyll content, and vapor pressure) were significantly enhanced by co-application of bacteria and zeolite ranging from 20 to 49% under Ni stress. Moreover, the combined utilization of bacteria and zeolite considerably improved water relations of sesame plant, in terms of relative water content (RWC) and relative membrane permeability (RMP) along with improvement in biochemical components (protein, ash, crude fiber, fat), and micronutrients in normal as well as in Ni contaminated soil. Moreover, the same treatment modulated the Ni-stress in plants through improvement in antioxidant enzymes (AEs) activities along with improved Ni concentration in the soil and different plant tissues. Correlation and principal component analysis (PCA) further revealed that combined application of metal-tolerant bacterium sp. MN13 and zeolite is the most influential strategy in alleviating Ni-induced stress and subsequent improvement in growth, yield, and physio-biochemical attributes of sesame plant.
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http://dx.doi.org/10.3390/ijerph17238859DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7730600PMC
November 2020

Performance of Zea mays L. cultivars in tannery polluted soils: Management of chromium phytotoxicity through the application of biochar and compost.

Physiol Plant 2020 Nov 20. Epub 2020 Nov 20.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia.

Soil contamination with heavy metals caused by various industrial activities is a threatening global environmental issue of the current era. Chromium (Cr) is the most toxic heavy metal used in leather industry and disposal of untreated wastewater into natural water bodies leads to contamination of natural soil and water resources. We studied the combined effect of biochar and compost on improving the tolerance to Cr toxicity by enhancing the morpho-physiological and biochemical attributes of two maize cultivars (P-1543 and NK-8441) grown in tannery waste polluted soils. The results of this study reveal that Cr toxicity reduced the plant growth by affecting physiological and biochemical attributes. Here, compost and biochar application significantly increased the plant biomass (fresh and dry), height, photosynthesis, chlorophyll content, water relation, starch, and protein content over treatment set as control. However, significant decline in electrolyte leakage (EL), proline, lipid peroxidation, soluble sugars, and antioxidant enzymes (APX, GPX, GR, GST, GSH, SOD, and CAT) was observed by combined application of compost and biochar. Hexavalent chromium concentration was maximum decreased to 4.1 μg g in soil after post-harvesting of maize cultivar NK-8441, while in roots and shoots to 22.6 and 19.2 μg g of maize cultivar P-1543, respectively, by combined application of compost and biochar. Moreover, these both amendments in combination showed considerably better results than their sole application and cultivar P-1543 comparatively performed better than NK 8441, in both K and S soils. Correlation and principal component analysis (PCA) revealed mostly highly positive associations among all the studied morpho, physio, and biochemical attributes of maize plant with the few exceptions, particularly concentration of Cr(III) and Cr(VI) in soil. The present work concluded that combined use of biochar and compost has great potential to decrease Cr toxicity and improve plant growth in tannery polluted soils.
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http://dx.doi.org/10.1111/ppl.13277DOI Listing
November 2020

Efficiency of Wheat Straw Biochar in Combination with Compost and Biogas Slurry for Enhancing Nutritional Status and Productivity of Soil and Plant.

Plants (Basel) 2020 Nov 8;9(11). Epub 2020 Nov 8.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.

In the present study, we investigated the impact of different combinations of wheat straw biochar, compost and biogas slurry on maize growth, physiology, and nutritional status in less productive soils. The experiment was performed as a completely randomized block design in a greenhouse pot experiment. The compost and biogas slurry were applied with and without biochar. The results revealed that a combination of biochar, compost, and biogas slurry enhanced the cation exchange capacity (31%), carbon (83%), phosphorus (67%) and potassium (81%) contents in the soil. Likewise, a significant increase in soil microbial biomass carbon (15%) and nitrogen (37%) was noticed with the combined use of all organic amendments. Moreover, the combined application of biochar, compost and biogas slurry enhanced soil urease and β-glucosidase activity up to 96% and 67% over control respectively. In addition, plant height, chlorophyll content, water use efficiency and 1000-grain weight were also enhanced up to 54%, 90%, 53% and 21% respectively, with the combined use of all amendments. Here, biochar addition helped to reduce the nutrient losses of compost and biogas slurry as well. It is concluded that biochar application in combination with compost and biogas slurry could be a more sustainable, environment-friendly and cost-effective approach, particularly for less fertile soils.
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http://dx.doi.org/10.3390/plants9111516DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695275PMC
November 2020

Synergistic Effect of IAGS 199 and Putrescine on Alleviating Cadmium-Induced Phytotoxicity in .

Plants (Basel) 2020 Nov 8;9(11). Epub 2020 Nov 8.

Department of Geology and Pedology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemedelska 3, 61300 Brno, Czech Republic.

Plant growth-promoting bacteria (PGPB) and putrescine (Put) have shown a promising role in the mitigation of abiotic stresses in plants. The present study was anticipated to elucidate the potential of IAGS 199 and Put in mitigation of cadmium (Cd)-induced toxicity in . Cadmium toxicity decreased growth, photosynthetic rate, gas exchange attributes and activity of antioxidant enzymes in seedlings. Moreover, higher levels of protein and non-protein bound thiols besides increased Cd contents were also observed in Cd-stressed plants. IAGS 199 and Put, alone or in combination, reduced electrolyte leakage (EL), hydrogen peroxide (HO) and malondialdehyde (MDA) level in treated plants. Synergistic effect of IAGS 199 and Put significantly enhanced the activity of stress-responsive enzymes including peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD). Furthermore, Put and microbial interaction enhanced the amount of proline, soluble sugars, and total soluble proteins in plants grown in Cd-contaminated soil. Data obtained during the current study advocates that application of IAGS 199 and Put establish a synergistic role in the mitigation of Cd-induced stress through modulating physiochemical features of plants.
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http://dx.doi.org/10.3390/plants9111512DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695146PMC
November 2020

Mitigation of arsenate toxicity by indole-3-acetic acid in brinjal roots: Plausible association with endogenous hydrogen peroxide.

J Hazard Mater 2021 Mar 24;405:124336. Epub 2020 Oct 24.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 2455, Saudi Arabia.

The role of indole-3-acetic acid (IAA) and hydrogen peroxide (HO) crosstalk in regulating metal stress is still less known. Herein, role of IAA in alleviating arsenate (As) toxicity in brinjal seedlings along with its probable relation with endogenous HO was investigated. Arsenate hampered root growth due to greater accumulation of As and decrease in phosphorus uptake that resulted into inhibited photosynthesis and cell death. Further, As induced oxidative stress markers and damage to macromolecules (lipids and proteins) due to alterations in redox status of glutathione as a result of inhibition in activity of glutathione synthetase and glutathione reductase. However, application of IAA with As improved root growth by significantly declining As accumulation and oxidative stress markers, sequestrating As into vacuoles, and improving redox status of glutathione which collectively protected roots from cell death. Interestingly, addition of diphenylene iodonium (DPI, an inhibitor of NADPH oxidase) further increased As toxicity even in the presence of IAA. However, application of HO rescued negative effect of DPI. Overall, the results suggested that in IAA-mediated mitigation of As toxicity in brinjal roots, endogenous HO might have acted as a downstream signal.
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http://dx.doi.org/10.1016/j.jhazmat.2020.124336DOI Listing
March 2021

Silver Nanoparticle Regulates Salt Tolerance in Wheat Through Changes in ABA Concentration, Ion Homeostasis, and Defense Systems.

Biomolecules 2020 11 2;10(11). Epub 2020 Nov 2.

Department of Botany, Jamia Hamdard, New Delhi 110062, India.

Salinity is major abiotic stress affecting crop yield, productivity and reduces the land-usage area for agricultural practices. The purpose of this study is to analyze the effect of green-synthesized silver nanoparticle (AgNP) on physiological traits of wheat () under salinity stress. Using augmented and high-throughput characterization of synthesized AgNPs, this study investigated the proximity of AgNPs-induced coping effects under stressful cues by measuring the germination efficiency, oxidative-biomarkers, enzymatic and non-enzymatic antioxidants, proline and nitrogen metabolism, stomatal dynamics, and ABA content. Taken together, the study shows a promising approach in salt tolerance and suggests that mechanisms of inducing the salt tolerance depend on proline metabolism, ions accumulation, and defense mechanisms. This study ascertains the queries regarding the correlation between nanoparticles use and traditional agriculture methodology; also significantly facilitates to reach the goal of sustainable developments for increasing crop productivity via much safer and greener approachability.
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http://dx.doi.org/10.3390/biom10111506DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7694077PMC
November 2020

Phosphorus Nutrient Management through Synchronization of Application Methods and Rates in Wheat and Maize Crops.

Plants (Basel) 2020 Oct 19;9(10). Epub 2020 Oct 19.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 2455, Saudi Arabia.

Management of inorganic fertilizer is very important to obtain maximum crop yield and improved nutrient use efficiency in cereal crops. Fixation of phosphatic fertilizers in alkaline soils due to calcareousness is one of the major hurdles. It induces phosphorus nutritional stress that can decrease the yield of maize and wheat. Selection of a suitable application method and proper stage of crop for phosphorus (P) fertilizer has prime importance in better uptake of P and crop production. Among different application methods, soil and foliar application are widely adopted. In wheat and maize, knee height + tasseling and stem elongation + booting are critical stages towards P deficiency. That is why field trials were conducted to evaluate the supplemental effect of foliar P on maize and wheat yields. For that, 144 mM KHPO was applied as foliar at knee height + tasseling and stem elongation + boot stages in maize and wheat, respectively. Soil application of 0, 20, 40 and 60 kg P ha was done through broadcast and band methods. Results showed that foliar spray of 144 mM KHPO at knee height + tasseling and stem elongation + boot stages in wheat and maize significantly enhanced grains yield and phosphorus use efficiency (PUE) where P was applied as banding or broadcast at the time of sowing. A significant decreasing trend in response to increasing soil P levels validated the efficacious role and suitability of foliar P. In conclusion, the use of P as foliar at knee height + tasseling and stem elongation + boot stages is an efficacious way to manage P fertilizer.
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http://dx.doi.org/10.3390/plants9101389DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7603365PMC
October 2020

Impact of Coating of Urea with -Augmented Zinc Oxide on Wheat Grown under Salinity Stress.

Plants (Basel) 2020 Oct 15;9(10). Epub 2020 Oct 15.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.

Zinc (Zn) availability is limited in salt-affected soils due to high soil pH and calcium concentrations causing Zn fixation. The application of synthetic Zn fertilizer is usually discouraged due to the high cost and low Zn use efficiency. However, salt-tolerant Zn-solubilizing bacteria (ZSB) are capable of solubilizing fixed fractions of Zn and improving fertilizer use efficiency. In the current study, a product was formulated by coating urea with bioaugmented zinc oxide (ZnO) to improve wheat productivity under a saline environment. The promising ZSB strain sp. AZ6 was used for bioaugmentation on ZnO powder and termed as sp. AZ6-augmented ZnO (BAZ). The experiment was conducted in pots by applying urea granules after coating with BAZ, to evaluate its effects on wheat physiology, antioxidant activity, and productivity under saline (100 mM NaCl) and non-saline (0 mM NaCl) conditions. The results revealed that the application of BAZ-coated urea alleviated salt stress through improving the seed germination, plant height, root length, photosynthetic rate, transpiration rate, stomatal conductance, soil plant analysis development (SPAD) value, number of tillers and grains, spike length, spike weight, 1000-grain weight, antioxidant activity (APX, GPX, GST, GR, CAT, and SOD), and NPK contents in the straw and grains of the wheat plants. Moreover, it also enhanced the Zn contents in the shoots and grains of wheat by up to 29.1 and 16.5%, respectively, over absolute control, under saline conditions. The relationships and variation among all the studied morpho-physio and biochemical attributes of wheat were also studied by principal component (PC) and correlation analysis. Hence, the application of such potential products may enhance nutrient availability and Zn uptake in wheat under salt stress. Therefore, the current study suggests the application of BAZ-coated urea for enhancing wheat's physiology, antioxidant system, nutrient efficiency, and productivity effectively and economically.
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http://dx.doi.org/10.3390/plants9101375DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7602814PMC
October 2020

Silicon-induced postponement of leaf senescence is accompanied by modulation of antioxidative defense and ion homeostasis in mustard (Brassica juncea) seedlings exposed to salinity and drought stress.

Plant Physiol Biochem 2020 Dec 7;157:47-59. Epub 2020 Oct 7.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 2455, Saudi Arabia. Electronic address:

Soil salinity and drought stress (DS) are the massive problem for worldwide agriculture. Both stresses together become more toxic to the plant growth and development. Silicon (Si) being the second most abundant element in the earth's crust, exerts beneficial effects on plants under both stress and non-stress conditions. However, limited information is available to substantiate the beneficial role of Si in delaying the premature leaf senescence and imparting tolerance of mustard (Brassica juncea L.) plants to salinity and DS. Therefore, the present study aimed to explore the role of Si (source KSiO) in chlorophyll (Chl) biosynthesis, nutrients uptake, relative water content (RWC), proline (Pro) metabolism, antioxidant system and delaying of premature leaf senescence in mustard plants under sodium chloride (NaCl) and DS conditions. Results of this study show that exogenous Si (1.7 mM) significantly delayed the salt plus DS-induced premature leaf senescence. This was further accompanied by the enhanced nutrients accumulation and activity of chlorophyll metabolizing enzymes [δ-aminolevulinic acid (δ-ALA) dehydratase and porphobilinogen deaminase] and levels of δ-ALA, and Chls a and b and also by decreased the Chl degradation and Chl degrading enzymes (Chlorophyllase, Chl-degrading peroxidase, pheophytinase) activity. Exogenous Si treatment induced redox homoeostasis in B. juncea L. plants, which is evident by a reduced generation of reactive oxygen species (ROS) resulting due to suppressed activity of their generating enzymes (glycolate oxidase and NADPH oxidase) and enhanced defence system. Furthermore, application of Si inhibited the activity of protease and triggered the activity of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) and plasma membrane H-ATPase activity. In conclusion, all these results reveal that Si could help in the modulation of Chl metabolism, redox hemostasis, and the regulation of nutrients (nitrogen, phosphorus, Si and potassium) uptake in the mustard plants that lead to the postponement of premature leaf senescence under salinity plus DS.
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http://dx.doi.org/10.1016/j.plaphy.2020.09.038DOI Listing
December 2020

Jasmonic acid: a key frontier in conferring abiotic stress tolerance in plants.

Plant Cell Rep 2020 Oct 9. Epub 2020 Oct 9.

Department of Agronomy, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka, 1207, Bangladesh.

Abiotic stresses are the primary sources of crop losses globally. The identification of key mechanisms deployed and established by plants in response to abiotic stresses is necessary for the maintenance of their growth and persistence. Recent discoveries have revealed that phytohormones or plant growth regulators (PGRs), mainly jasmonic acid (JA), have increased our knowledge of hormonal signaling of plants under stressful environments. Jasmonic acid is involved in various physiological and biochemical processes associated with plant growth and development as well as plant defense mechanism against wounding by pathogen and insect attacks. Recent findings suggest that JA can mediate the effect of abiotic stresses and help plants to acclimatize under unfavorable conditions. As a vital PGR, JA contributes in many signal transduction pathways, i.e., gene network, regulatory protein, signaling intermediates and enzymes, proteins, and other molecules that act to defend cells from the harmful effects of various environmental stresses. However, JA does not work as an independent regulator, but acts in a complex signaling pathway along other PGRs. Further, JA can protect and maintain the integrity of plant cells under several stresses by up-regulating the antioxidant defense. In this review, we have documented the biosynthesis and metabolism of JA and its protective role against different abiotic stresses. Further, JA-mediated antioxidant potential and its crosstalk with other PGRs have also been discussed.
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http://dx.doi.org/10.1007/s00299-020-02614-zDOI Listing
October 2020

Crosstalk of hydrogen sulfide and nitric oxide requires calcium to mitigate impaired photosynthesis under cadmium stress by activating defense mechanisms in Vigna radiata.

Plant Physiol Biochem 2020 Nov 16;156:278-290. Epub 2020 Sep 16.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 2455, Saudi Arabia.

Hydrogen sulfide (HS) and nitric oxide (NO) have been known to affect vast number of processes in plants under abiotic stresses. Also, calcium (Ca) works as a second messenger in plants, which underpins the abiotic stress-induced damage. However, the sequence of action of these signaling molecules against cadmium (Cd)-induced cellular oxidative damage remains unidentified. Therefore, we studied the synergistic actions and/or relationship of signaling molecules and Ca-dependent activation of tolerance mechanisms in Vigna radiata seedlings under Cd stress. The present study shows that exogenous Ca supplemented to Cd-stressed V. radiata seedlings reduced Cd accumulation and improved the activity of nitrate reductase, and L/D-cysteine desulfhydrase (LCD/DCD) that resulted in improved synthesis of NO and HS content. Application of Ca also elevated the level of cysteine (Cys) by upregulating the activity of Cys-synthesizing enzymes serine acetyltransferase and O-acetylserine(thiol)lyase in Cd-stressed seedlings. Maintenance of Cys pool under Cd stress contributed to improved HS content which together with Ca and NO improved antioxidant enzymes and components of ascorbate-glutathione (AsA-GSH) cycle. All these collectively regulated the activity of NADPH oxidase and glycolate oxidase, resulting in the inhibition of Cd-induced generation of reactive oxygen species. The elevated level of Cys also assisted the Cd-stressed seedlings in maintaining GSH pool which retained normal functioning of AsA-GSH cycle and led to enhanced content of phytochelatins coupled with reduced Cd content. The positive effect of these events manifested in an enhanced rate of photosynthesis, carbohydrate accumulation, and growth attributes of the plants. On the contrary, addition of NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide], HS scavenger HT (Hypotaurine) and Ca-chelator EGTA (Ethylene glycol-bis(b-aminoethylether)-N,N,N',N'-tetraacetic acid) again developed a condition similar to stress and positive effect of the signaling molecules was abolished. The findings of the study postulate that Ca in association with NO and HS mitigates Cd-induced impairment and enhances the tolerance of the V. radiata plants against Cd stress. The results of the study also substantiate that Ca acts both upstream as well as downstream of NO signals whereas, HS acts downstream of Ca and NO during Cd-stress responses of the plants.
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http://dx.doi.org/10.1016/j.plaphy.2020.09.017DOI Listing
November 2020

Polyamine Metabolism, Photorespiration, and Excitation Energy Allocation in Photosystem II Are Potentially Regulatory Hubs in Poplar Adaptation to Soil Nitrogen Availability.

Front Plant Sci 2020 26;11:1271. Epub 2020 Aug 26.

State Key Laboratory of Tree Genetics and Breeding, School of Forestry, Northeast Forestry University, Harbin, China.

Nitrogen fertilization is common for poplar trees to improve growth and productivity. The utilization of N by poplar largely depends on fertilizer application patterns; however, the underlying regulatory hubs are not fully understood. In this study, N utilization and potentially physiological regulations of two poplar clones (XQH and BC5) were assessed through two related experiments (i: five levels of N supply and ii: conventional and exponential N additions). Poplar growth (leaf area) and N utilization significantly increased under fertilized compared to unfertilized conditions, whereas photosynthetic N utilization efficiency significantly decreased under low N supplies. Growth characteristics were better in the XQH than in the BC5 clone under the same N supplies, indicating higher N utilization efficiency. Leaf absorbed light energy, and thermal dissipation fraction was significantly different for XQH clone between conventional and exponential N additions. Leaf concentrations of putrescine (Put) and acetylated Put were significantly higher in exponential than in conventional N addition. Photorespiration significantly increased in leaves of XQH clone under exponential compared to conventional N addition. Our results indicate that an interaction of the clone and N supply pattern significantly occurs in poplar growth; leaf expansion and the storage N allocations are the central hubs in the regulation of poplar N utilization.
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http://dx.doi.org/10.3389/fpls.2020.01271DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7479266PMC
August 2020

Full sunlight acclimation mechanisms in Riccia discolor thalli: Assessment at morphological, anatomical, and biochemical levels.

J Photochem Photobiol B 2020 Sep 31;210:111983. Epub 2020 Jul 31.

Plant Physiology Laboratory, Department of Botany, C.M.P. Degree College, A Constituent Post Graduate College of University of Allahabad, Prayagraj 211002, India. Electronic address:

Light occupies a central position in regulating development of plants. Either little or excess of light could be harmful for plants. Since bryophytes are shade loving organisms, they must adapt to function in fluctuating light regimes. Therefore, the aim of this study was to investigate acclimatory responses of Riccia discolor thalli grown under full sunlight, and were compared with shade grown thalli (control). Length, width, and fresh mass of thallus were significantly lower (by 27, 41 and 37%, respectively) but endogenous nitric oxide content (by 81%) and nitric oxide synthase like activity (by 58%) were higher in full sunlight grown thalli than shade grown thalli. Number of rhizoids was greater in shade but length and width of rhizoids were higher (by 36 and 25%, respectively) in full sunlight grown thalli. The content of carotenoids was higher (by 34%) in full sunlight grown thalli. In full sunlight grown thalli, chloroplasts exhibited avoidance movement but in shade grown thalli they exhibited accumulation movement. Photosynthetic yields were higher in shade grown thalli. Among energy fluxes, ABS/RC did not vary but DI/RC was higher (by 12%) in full sunlight grown thalli. Reactive oxygen species and damage were greater in full sunlight grown thalli despite enhanced levels of antioxidants i.e. superoxide dismutase (by 66%) and catalase (by 34%). Overall results suggest that full sunlight acclimation in Riccia discolor thalli occurred at various levels in which endogenous NO plays a positive role.
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http://dx.doi.org/10.1016/j.jphotobiol.2020.111983DOI Listing
September 2020

Exogenous nitric oxide requires endogenous hydrogen sulfide to induce the resilience through sulfur assimilation in tomato seedlings under hexavalent chromium toxicity.

Plant Physiol Biochem 2020 Oct 20;155:20-34. Epub 2020 Jul 20.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia. Electronic address:

Nitric oxide (NO) and hydrogen sulfide (HS), versatile signaling molecules, play multiple roles in plant growth, physiological and biochemical processes under heavy metal stress. However, the mechanisms through which NO in association with endogenous HS mediated hexavalent chromium Cr(VI) toxicity mitigation are still not fully understood. Therefore, we investigated the role of NO and HS in sulfur (S)-assimilation and the effect of NO on endogenous HS, and cysteine (Cys) biosynthesis and maintenance of cellular glutathione (GSH) pool in tomato seedlings under Cr(VI) stress. Cr(VI) toxicity caused an increase in reactive oxygen species (ROS; O and HO) formation and activity of chlorophyll (Chl) degrading enzyme [Chlorophyllase (Chlase)] and decrease in seedlings growth attributes, Chl a and b content, and activity of Chl synthesizing enzyme [δ-aminolevulinic acid dehydratase (δ-ALAD)], gas exchange parameters, S-assimilation, and Cys and HS metabolism. An increase in the content of glycinebetaine (GB), total soluble carbohydrates (TSCs) and total phenols (TPls), and decrease in DNA damage and ROS in NO treated seedlings conferred Cr(VI) toxicity tolerance. Under Cr(VI) toxicity conditions, the inclusion of HS scavenger hypotaurine (HT) in growth medium containing NO validated the role of endogenous HS in S-assimilation, HS and Cys and GSH metabolism by withdrawing activity of enzymes involved in S-assimilation [adenosine 5-phosphosulfatereductase (APS-R), ATP-sulfurylase (ATP-S)], in the biosynthesis of HS [L-cysteine desulfhydrase (L-CD) and D-cysteine desulfhydrase (D-CD)], Cys [O-acetylserin (thiol) lyase (OAST-L)], and GSH [glutamylcysteine synthetase (γ-GCS) and glutathione synthetase (GS)], and in antioxidant system. On the other hand, application of cPTIO [2-(4-32 carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide], a NO scavenger and HT diminished the effect of NO on internal HS levels, Cys and glutathione homeostasis, and S-assimilation, which resulted in poor immunity against oxidative stress induced by Cr(VI) toxicity. The obtained results postulate that NO-induced internal HS conferred tolerance of tomato seedlings to Cr(VI) toxicity and maintained better photosynthesis process and plant growth.
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http://dx.doi.org/10.1016/j.plaphy.2020.07.003DOI Listing
October 2020

Ascorbic acid is essential for inducing chromium (VI) toxicity tolerance in tomato roots.

J Biotechnol 2020 Oct 15;322:66-73. Epub 2020 Jul 15.

Chair of Climate Change, Environmental Development and Vegetation Cover, Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia. Electronic address:

Problem of chromium (Cr) pollution is of great scientific concern as it adversely affects crop productivity worldwide. Therefore, scientific efforts are being made to minimize Cr toxicity in crop plants by using various methods. Of these methods, use of certain chemicals like ascorbic acid (ASC), glutathione, proline, nutrients, etc. has shown promising results. Therefore, in this study, we have tested a role of ASC in regulating hexavalent chromium [Cr(VI)] toxicity in tomato roots. Chromium (VI) reduced length, dry weight, fitness and tissue density of roots due to enhanced cellular accumulation of Cr which leads to the cell death. Chromium (VI) also declined ASC pool and activity of its regenerating enzymes along with enhanced level of oxidative stress and damage to lipids and proteins. However, exogenous addition of ASC significantly reversed toxic effects of Cr(VI) in tomato roots. Furthermore, addition of lycorine (inhibitor of ASC biosynthesis) interestingly augmented Cr(VI) toxicity. However, exogenous addition of ASC reversed toxic effect of lycorine suggesting that endogenous ASC has role in alleviating Cr(VI) toxicity in tomato roots.
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http://dx.doi.org/10.1016/j.jbiotec.2020.07.011DOI Listing
October 2020

Dose dependent differential effects of toxic metal cadmium in tomato roots: Role of endogenous hydrogen sulfide.

Ecotoxicol Environ Saf 2020 Oct 13;203:110978. Epub 2020 Jul 13.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia. Electronic address:

In this study, hydroponic experiments were conducted to elucidate mechanism(s) that are associated with differential effects of low (5 μM) and high (25 μM) dose of cadmium (Cd) stress in tomato. Furthermore, emphasis has also been focused on any involvement of endogenous hydrogen sulfide (HS) in differential behaviour of low and high doses of Cd stress. At low dose of Cd, root growth i.e. root fresh weight, length and fitness did not significantly alter when compared to the control seedlings. Though at low dose of Cd, cellular accumulation of Cd was slightly increased but this was accompanied by higher endogenous HS and phytochelatins, -cysteine desulfhydrase (DES) activity, activities of glutathione biosynthetic and AsA-GSH cycle enzymes, and maintained redox status of ascorbate and glutathione. However, addition of hypotaurine (HT, a scavenger of HS) resulted in greater toxicity, even at low dose of Cd, and these responses resembled with higher dose of Cd stress such as greater decline in root growth, endogenous HS and phytochelatins, activities of DES, glutathione biosynthesis and AsA-GSH cycle enzymes, disturbed redox status of ascorbate and glutathione which collectively led to higher oxidative stress in tomato roots. Moreover, addition of HT with higher dose of Cd also further enhanced its toxicity. Collectively, the results showed that differential behaviour of low and high dose of Cd stress is mediated by differential regulation of biochemical attributes in which endogenous HS has a crucial role.
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http://dx.doi.org/10.1016/j.ecoenv.2020.110978DOI Listing
October 2020

Priming of tomato seedlings with 2-oxoglutarate induces arsenic toxicity alleviatory responses by involving endogenous nitric oxide.

Physiol Plant 2020 Jul 12. Epub 2020 Jul 12.

Department of Botany and Microbiology, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia.

Metal toxicity in crop plants is a matter of scientific concern. Therefore, in recent years efforts have been made to minimize metal toxicity in crop plants. Out of various strategies, priming of seedlings with certain chemicals, like e.g. donors of signaling molecules, nutrients, metabolites or plant hormones has shown encouraging results. However, mechanisms related with the priming-induced mitigation of metal toxicity are still poorly known. Hence, we have tested the potential of 2-oxoglutarate (2-OG) priming in enhancing the arsenate (As ) toxicity tolerance in tomato seedlings along with deciphering the probable role of nitric oxide (NO) in accomplishing this task. Arsenate decreased growth, endogenous NO and nitric oxide synthase-like activity but enhanced the accumulation of As, which collectively led to root cell death. Arsenate toxicity also decreased some photosynthetic characteristics (i.e. F /F qP, F /F and F /F , and total chlorophyll content) but enhanced NPQ. However, priming with 2-OG alleviated the toxic effect of As on growth, endogenous NO, cell death and photosynthesis. Moreover, arsenate inhibited the activities of enzymes of nitrogen metabolism (i.e. nitrate reductase, nitrite reductase, glutamine synthetase and glutamine 2-oxoglutarate aminotransferase) but increased the activity of glutamate dehydrogenase and NH content. Superoxide radicals, hydrogen peroxide, lipid peroxidation, protein oxidation and membrane damage increased upon As exposure, but the antioxidant enzymes (i.e. superoxide dismutase, catalase and glutathione-S-transferase) showed differential responses. Overall, our results showed that 2-OG is capable of alleviating As toxicity in tomato seedlings but the involvement of endogenous NO is probably required.
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http://dx.doi.org/10.1111/ppl.13168DOI Listing
July 2020

Integration of silicon and secondary metabolites in plants: a significant association in stress tolerance.

J Exp Bot 2020 Dec;71(21):6758-6774

Botany and Microbiology Department, College of Science, King Saud University, Riyadh, Saudi Arabia.

As sessile organisms, plants are unable to avoid being subjected to environmental stresses that negatively affect their growth and productivity. Instead, they utilize various mechanisms at the morphological, physiological, and biochemical levels to alleviate the deleterious effects of such stresses. Amongst these, secondary metabolites produced by plants represent an important component of the defense system. Secondary metabolites, namely phenolics, terpenes, and nitrogen-containing compounds, have been extensively demonstrated to protect plants against multiple stresses, both biotic (herbivores and pathogenic microorganisms) and abiotic (e.g. drought, salinity, and heavy metals). The regulation of secondary metabolism by beneficial elements such as silicon (Si) is an important topic. Silicon-mediated alleviation of both biotic and abiotic stresses has been well documented in numerous plant species. Recently, many studies have demonstrated the involvement of Si in strengthening stress tolerance through the modulation of secondary metabolism. In this review, we discuss Si-mediated regulation of the synthesis, metabolism, and modification of secondary metabolites that lead to enhanced stress tolerance, with a focus on physiological, biochemical, and molecular aspects. Whilst mechanisms involved in Si-mediated regulation of pathogen resistance via secondary metabolism have been established in plants, they are largely unknown in the case of abiotic stresses, thus leaving an important gap in our current knowledge.
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http://dx.doi.org/10.1093/jxb/eraa291DOI Listing
December 2020

Exogenous melatonin mitigates boron toxicity in wheat.

Ecotoxicol Environ Saf 2020 Sep 11;201:110822. Epub 2020 Jun 11.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 2455, Saudi Arabia.

Boron (B) toxicity is an important abiotic constraint that limits crop productivity mainly in arid and semi-arid areas of the world. High levels of B in soil disturbs several physiological and biochemical processes in plant. The aim of this study was to investigate the function of melatonin (Mel) in the regulation of carbohydrate and proline (Pro) metabolism, photosynthesis process and antioxidant system of wheat seedlings under B toxicity conditions. High levels of B inhibited net photosynthetic rate (P), stomatal conductance (g), content of chlorophyll (Chl) a, b, δ-aminolevulinic acid (δ-ALA), nitrogen (N) and phosphorus (P), and increased accumulation of B, Chl degradation and activity of chlorophyllase (Chlase; a Chl degrading enzyme), and downregulated the activity of enzymes (δ-ALAD; δ-aminolevulinic acid dehydratase) involved in the biosynthesis of photosynthesis pigments, photosynthesis (carbonic anhydrase and ribulose-1,5-bisphosphate carboxylase/oxygenase) and carbohydrate metabolism (cell wall invertase, CWI) in wheat seedlings. Also, high levels of B caused oxidative damage by increasing the content of malondialdehyde, superoxide anion and HO, and activity of glycolate oxidase (an HO-producing enzyme) in leaves of seedlings. However, foliar application of Mel significantly improved photosynthetic pigments concentration by increasing δ-ALA, δ-ALAD and decreasing Chl degradation and Chlase activity and led to an increase of plant growth attributes under both B toxicity and non-toxicity conditions. Under normal and B toxicity conditions, exogenous Mel also improved content of N, P, total soluble carbohydrates (TSCs) and Pro, and upregulated activity of CWI and Δ-pyrroline-5-carboxylate synthetase. Mel significantly suppressed the adverse effects of excess B by alleviating cellular oxidative damage through enhanced reactive oxygen species scavenging by superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and lipoxygenase, and content of total phenolic compounds (TPC), ascorbate and reduced glutathione. These results postulate that Mel induced plant defense mechanisms by enhancing Pro, TSCs, TPC, nutrients (N and P) uptake and enzymatic and non-enzymatic antioxidants.
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http://dx.doi.org/10.1016/j.ecoenv.2020.110822DOI Listing
September 2020

Melatonin and calcium function synergistically to promote the resilience through ROS metabolism under arsenic-induced stress.

J Hazard Mater 2020 11 15;398:122882. Epub 2020 May 15.

Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 2455, Saudi Arabia.

The interplay between melatonin (Mel) and calcium (Ca) in enhancing tolerance to metalloid toxicity and underlying physiological and biochemical mechanisms of this relationship still remains unknown. The present study reveals that the signaling molecules Mel and/or Ca enhanced tolerance of Vicia faba (cv. Tara) plant to metalloid arsenic (As) toxicity. However, a combination of Mel and Ca was more efficient than alone. Plants grew with As exhibited enhanced hydrogen peroxide, superoxide anion, electrolyte leakage, lipid peroxidation together with increased reactive oxygen species (ROS) producing enzymes, such as NADPH oxidase and glycolate oxidase (GOX). On the contrary, an inhibition in chlorophyll (Chl) biosynthesis and gas exchange parameters (net photosynthetic rate, stomatal conductance, intercellular carbon dioxide concentration) was observed. Under As toxicity conditions, the application of Mel and Ca synergistically suppressed the plants' program cell death features (nucleus condensation and nucleus fragmentation) in guard cells of stomata, DNA damage, and formation of ROS in guard cells, leaves and roots. Moreover, it enhanced gas exchange parameters and activity of enzymes involved in photosynthesis process (carbonic anhydrase and RuBisco), Chl biosynthesis (δ-aminolevulinic acid dehydratase), and decreased activity of Chl degrading enzyme (chlorophyllase) under As toxicity conditions. Our investigation evidently established that expression of ATP synthase, Ca-ATPase, Ca-DPKase, Hsp17.6 and Hsp40 was found maximum in the plants treated with Mel + Ca, resulting in higher tolerance of plants to As stress. Also, increased total soluble carbohydrates, cysteine, and Pro accumulation with increased Pro synthesizing enzyme (Δ-pyrroline-5-carboxylate synthetase (P5CS) and decreased Pro degrading enzyme (proline dehydrogenase) in Mel + Ca treated plants conferred As toxicity tolerance. The obtained results postulate strong evidence that the application of Mel along with Ca enhances resilience against As toxicity by upregulating the activity of plasma membrane H-ATPase, enzymes involved in antioxidant system, and ascorbate-glutathione pathway.
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http://dx.doi.org/10.1016/j.jhazmat.2020.122882DOI Listing
November 2020

Potentials of organic manure and potassium forms on maize (Zea mays L.) growth and production.

Sci Rep 2020 05 29;10(1):8752. Epub 2020 May 29.

Botany and Microbiology Department, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia.

Worldwide, maize (Zea mays L.) is considered an important food and fodder crop. Compost as a soil amendment and potassium (K) could enhance the maize yield. Therefore, two field experiments were carried out in the two seasons 2017 and 2018 to study the effects of compost at three levels and four forms of potassium fertilization on the yellow maize hybrid 'Pioneer SC 30N11' yield components. To conduct the field trials, a split plot system in three replications was established. Three compost levels (0, 5 and 10 ton/ha) were in the main plots, and four potassium forms (untreated, nano-potassium fertilizer, humic acid and potassium sulfate) were in the subplots. Plot size was 10.50 m, with 5 ridges with 3 m length and 0.7 m width. The results indicated that the application of compost (as organic manure) and the potassium forms significantly affected the plant height, ear length, grains number/rows, grains number/ear, 100- grain weight, straw and biological yields, grain protein and K contents in both seasons. Increasing the compost from 5 to 10 ton/ha increased the yield, its components, protein and K contents. The foliar application of nano-potassium followed by humic acid increased all the studied characteristics. The interaction between compost manure (10 ton/ha) and nano-potassium (500 cm/ha) or humic acid (10 ton/ha) recorded the highest mean values for all parameters during both harvest seasons.
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http://dx.doi.org/10.1038/s41598-020-65749-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7260245PMC
May 2020

Nitric oxide-mediated regulation of sub-cellular chromium distribution, ascorbate-glutathione cycle and glutathione biosynthesis in tomato roots under chromium (VI) toxicity.

J Biotechnol 2020 Jul 19;318:68-77. Epub 2020 May 19.

Plant Physiology Laboratory, Department of Botany, C.M.P. Degree College, A Constituent Post Graduate College of University of Allahabad, Prayagraj, 211002, India. Electronic address:

Unprecedented anthropogenic activities have led to contamination of soil and water with toxic metals that present a great threat to crop yields. This situation has compelled researchers to understand metal toxicity responses in order to develop strategies to curtail toxic metal-mediated losses in crop yields. Past decade has witnessed tremendous developments with regard to the role of nitric oxide (NO) in regulating abiotic stresses including toxic metal in crop plants. However, mechanisms related with NO-mediated mitigation of metal toxicity are still less known, and thus investigation in this domain remains underway. Therefore, in this study potential of NO along with its mechanisms of action in mitigating hexavalent chromium [Cr(VI)] toxicity in tomato roots were investigated. Root length and dry weight were declined by Cr(VI) which coincided with increased accumulation of Cr. Major amount of Cr was in the cell wall fraction followed by soluble (including vacuoles) and cell organelles fraction and thus, leading to the cell death in roots. Further, Cr(VI) also declined endogenous NO by inhibiting nitric oxide synthase like activity, and down-regulated ascorbate-glutathione cycle and glutathione biosynthesis, but stimulated oxidative stress markers. In contrast, exogenous addition of NO (as a sodium nitroprusside) reduced toxic effects of Cr(VI) in tomato roots by decreasing Cr accumulation as well as triggering sequestration of Cr into vacuoles and thus collectively protect root from cell death. Moreover, NO also up-regulated ascorbate-glutathione cycle and glutathione biosynthesis, and stimulated phytochelatins, but greatly declined oxidative stress markers. Interestingly, addition of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO) further worsened Cr(VI) toxicity, and Cr(VI) toxicity alleviatory effect of NO was partly reversed by the addition of c-PTIO, suggesting that NO has a crucial role in rendering Cr(VI) toxicity tolerance in tomato roots. Collectively, results suggest that NO mitigates Cr(VI) toxicity in tomato roots by reducing Cr and oxidative stress markers accumulation, triggering sequestration of Cr into vacuoles, and up-regulating ascorbate-glutathione cycle and glutathione biosynthesis, and phytochelatins.
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http://dx.doi.org/10.1016/j.jbiotec.2020.05.006DOI Listing
July 2020

Soil Application of Nano Silica on Maize Yield and Its Insecticidal Activity Against Some Stored Insects After the Post-Harvest.

Nanomaterials (Basel) 2020 Apr 12;10(4). Epub 2020 Apr 12.

Plant Production Department, Faculty of Agriculture (Saba Basha), Alexandria University, P.O. Box 21531 Alexandria, Egypt.

Maize is considered one of the most imperative cereal crops worldwide. In this work, high throughput silica nanoparticles (SiO-NPs) were prepared via the sol-gel technique. SiO-NPs were attained in a powder form followed by full analysis using the advanced tools (UV-vis, HR-TEM, SEM, XRD and zeta potential). To this end, SiO-NPs were applied as both nanofertilizer and pesticide against four common pests that infect the stored maize and cause severe damage to crops. As for nanofertilizers, the response of maize hybrid to mineral NPK, "Nitrogen (N), Phosphorus (P), and Potassium (K)" (0% = untreated, 50% of recommended dose and 100%), with different combinations of SiO-NPs; (0, 2.5, 5, 10 g/kg soil) was evaluated. Afterward, post-harvest, grains were stored and fumigated with different concentrations of SiO-NPs (0.0031, 0.0063. 0.25, 0.5, 1.0, 2.0, 2.5, 5, 10 g/kg) in order to identify LC and mortality % of four common insects, namely and . The results revealed that, using the recommended dose of 100%, mineral NPK showed the greatest mean values of plant height, chlorophyll content, yield, its components, and protein (%). By feeding the soil with SiO-NPs up to 10 g/kg, the best growth and yield enhancement of maize crop is noticed. Mineral NPK interacted with SiO-NPs, whereas the application of mineral NPK at the rate of 50% with 10 g/kg SiO-NPs, increased the highest mean values of agronomic characters. Therefore, SiO-NPs can be applied as a growth promoter, and in the meantime, as strong unconventional pesticides for crops during storage, with a very small and safe dose.
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http://dx.doi.org/10.3390/nano10040739DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7221732PMC
April 2020

Nitric oxide is involved in nano-titanium dioxide-induced activation of antioxidant defense system and accumulation of osmolytes under water-deficit stress in Vicia faba L.

Ecotoxicol Environ Saf 2020 Mar 9;190:110152. Epub 2020 Jan 9.

Chair of Climate Change, Environmental Development and Vegetation Cover, Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.

Nano-titanium dioxide (nTiO) has been reported to improve tolerance of plants against different environmental stresses by modulating various physiological and biochemical processes. Nitric oxide (NO) has been shown to act as an important stress signaling molecule during plant responses to abiotic stresses. The present work was planned to investigate the involvement of endogenous NO in nTiO-induced activation of defense system of fava bean (Vicia faba L.) plants under water-deficit stress (WDS) conditions. Water-suffered plants showed increased concentration of hydrogen peroxide (HO) and superoxide (O) content coupled with increased electrolyte leakage and lipid peroxidation which adversely affected nitrate reductase (NR) activity, chlorophyll content and growth of the plants. However, application of 15 mg L nTiO to stressed plants significantly induced NR activity and synthesis of NO which elevated enzymatic and non-enzymatic defense system of the stressed plants and suppressed the generation of HO and O content, leakage of electrolytes, and lipid peroxidation. Application of nTiO, in association with NO, also enhanced the accumulation of osmolytes (proline and glycine betaine) that assisted the stressed plants in osmotic adjustment as witnessed by improved hydration level of the plants. Involvement of NO in nTiO-induced activation of defense system was confirmed with NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] which caused recurrence of WDS.
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http://dx.doi.org/10.1016/j.ecoenv.2019.110152DOI Listing
March 2020

Exogenous nitric oxide alleviates sulfur deficiency-induced oxidative damage in tomato seedlings.

Nitric Oxide 2020 01 7;94:95-107. Epub 2019 Nov 7.

Department of Plant Production, College of Food and Agricultural Sciences, King Saud University, P.O. Box 2460, Riyadh, 11451, Saudi Arabia.

Despite numerous reports on the role of nitric oxide (NO) in regulating plants growth and mitigating different environmental stresses, its participation in sulfur (S) -metabolism remains largely unknown. Therefore, we studied the role of NO in S acquisition and S-assimilation in tomato seedlings under low S-stress conditions by supplying NO to the leaves of S-sufficient and S-deficient seedlings. S-starved plants exhibited a substantial decreased in plant growth attributes, photosynthetic pigment chlorophyll (Chl) and other photosynthetic parameters, and activity of enzymes involved in Chl biosynthesis (δ-aminolevulinic acid dehydratase), and photosynthetic processes (carbonic anhydrase and RuBisco). Also, S-deficiency enhanced reactive oxygen species (ROS) (superoxide and hydrogen peroxide) and lipid peroxidation (malondialdehyde) levels in tomato seedlings. Contrarily, foliar supplementation of NO to S-deficient seedlings resulted in considerably reduced ROS formation in leaves and roots, which alleviated low S-stress-induced lipid peroxidation. However, exogenous NO enhanced proline accumulation by increasing proline metabolizing enzyme (Δ-pyrroline-5-carboxylate synthetase) activity and also increased NO, hydrogen sulfide (a gasotransmitter small signaling molecule) and S uptake, and content of S-containing compounds (cysteine and reduced glutathione). Under S-limited conditions, NO improved S utilization efficiency of plants by upregulating the activity of S-assimilating enzymes (ATP sulfurylase, adenosine 5-phosphosulfate reductase, sulfide reductase and O-acetylserine (thiol) lyase). Under S-deprived conditions, improved S-assimilation of seedlings receiving NO resulted in improved redox homeostasis and ascorbate content through increased NO and S uptake. Application of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxy l-3-oxide (an NO scavenger) invalidated the effect of NO and again caused low S-stress-induced oxidative damage, confirming the beneficial role of NO in seedlings under S-deprived conditions. Thus, exogenous NO enhanced the tolerance of tomato seedlings to limit S-triggered oxidative stress and improved photosynthetic performance and S assimilation.
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http://dx.doi.org/10.1016/j.niox.2019.11.002DOI Listing
January 2020