Saud A. Alamri

Improvement of salt and waterlogging tolerance in wheat: comparative physiology of Hordeum marinum-Triticum aestivum amphiploids with their H. marinum and wheat parents

Hordeum marinum Huds. is a waterlogging-tolerant halophyte that has been hybridised with bread wheat (Triticum aestivum L.) to produce an amphiploid containing both genomes. This study tested the hypothesis that traits associated with waterlogging and salinity tolerances would be expressed in H. marinum-wheat amphiploids. Four H. marinum accessions were used as parents to produce amphiploids with Chinese Spring wheat, and their responses to hypoxic and 200mM NaCl were evaluated. Relative growth rate (RGR) in the hypoxic-saline treatment was better maintained in the amphiploids (58-71% of controls) than in wheat (56% of control), but the amphiploids were more affected than H. marinum (68-97% of controls). In hypoxic-saline conditions, leaf Na+ concentrations in the amphiploids were lower than in wheat (30-41% lower) but were 39-47% higher than in the H. marinum parents. A strong barrier to radial oxygen loss formed in basal root zones under hypoxic conditions in two H. marinum accessions; this barrier was moderate in the amphiploids, absent in wheat, and was weaker for the hypoxic-saline treatment. Porosity of adventitious roots increased with the hypoxic treatments; values were 24-38% in H. marinum, 16-27% in the amphiploids and 16% in wheat. Overall, the amphiploids showed greater salt and waterlogging tolerances than wheat, demonstrating the expression of relevant traits from H. marinum in the amphiploids.

Jasmonic acid alleviates negative impacts of cadmium stress by modifying osmolytes and antioxidants in faba bean (Vicia faba L.)

ABSTRACT We examined the role of jasmonic acid (JA) in faba bean under cadmium (Cd) stress, which reduces the growth, biomass yield, leaf relative water content (LRWC) and pigment systems. Hydrogen peroxide (H2O2) and lipid peroxidation (malondialdehyde [MDA]) levels increased by 2.78 and 2.24-fold, respectively, in plants under Cd stress, resulting in enhanced electrolyte leakage. Following foliar application to Cd-treated plants, JA restored growth, biomass yield, LRWC and pigment systems to appreciable levels and reduced levels of H2O2, MDA and electrolyte leakage. Proline and glycine betaine concentrations increased by 5.73 and 2.61-fold, respectively, in faba bean under Cd stress, with even higher concentrations observed following JA application to Cd-stressed plants. Superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase levels rose by 87.47%, 130.54%, 132.55% and 37.79%, respectively, with Cd toxicity, with further enhancement of antioxidant activities observed following foliar application of JA. Accumulation of Cd in roots, shoots and leaves was also minimized by external supplementation of JA. In conclusion, JA mitigates the negative impacts of Cd stress in faba bean plants by inhibiting the accumulation of Cd, H2O2 and MDA, and by enhancing osmolyte and antioxidant activities that reduce oxidative stress.

Sodium nitroprusside and indole acetic acid improve the tolerance of tomato plants to heat stress by protecting against DNA damage

ABSTRACT Climate change represents a major threat to agriculture. High ambient temperatures, as a result of global warming, are currently limiting plant growth and development. The aim of the present study was to investigate the effect of sodium nitroprusside (SNP) in combination with indole acetic acid (IAA) on tomato (Lycopersicon esculentum Mill.) plants under heat stress (HS) and non-heat stress (non-HS) conditions. HS is suggested to induce the formation of reactive oxygen species, such as superoxide and hydrogen peroxide, which may lead to genotoxicity by damaging DNA, which can be detected by the comet assay (single-cell gel electrophoresis). HS substantially enhanced proline (Pro), malondialdehyde accumulation, electrolyte leakage (EL), growth reduction, and reduced physiological and biochemical parameters. However, the co-application of SNP and IAA alleviated the adverse effects of HS by promoting catalase, peroxidase, and superoxide dismutase activities and enhancing the accumulation of photosynthetic pigments (chlorophyll a and b) and Pro with a concomitant decrease in H2O2 and content, EL, and DNA damage. Conversely, the treatment of tomato plants with the NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] along with SNP and IAA further reduced the SNP signal. Therefore, these results suggest that the application of SNP with IAA improves plant defense mechanisms against HS.

Bacillus firmus (SW5) augments salt tolerance in soybean (Glycine max L.) by modulating root system architecture, antioxidant defense systems and stress-responsive genes expression

Soil salinity is an adverse abiotic factor which reduces plant growth, yield and quality. Plant growth-promoting rhizobacteria (PGPR) have a great potential to enhance growth and alleviate saline stress effects without harming the environment via regulating physiological and molecular processes in plants. This study aimed at investigating Bacillus firmus SW5 effects on the performance of soybean (Glycine max L.) subjected to salt stress (0, 40 and 80 mM NaCl). Salinity stress mitigated the growth and biomass yield, root architecture traits, nutrient acquisition, chlorophyll level, transpiration rate (E), photosynthesis rate (Pn), stomatal conductance (gs), soluble proteins content, soluble sugars content and total phenolics and flavonoid contents of soybean plants. High salinity augmented the levels of osmolytes (glycine betaine and proline), hydrogen peroxide (H2O2), malondialdehyde (MDA) and the activities of antioxidant enzymes (APX, CAT, SOD and POD) in soybean plants. High salinity also induced the expression of antioxidant enzyme-encoding genes (APX, CAT, POD, Fe-SOD) and genes conferring tolerance to salinity (GmVSP, GmPHD2, GmbZIP62, GmWRKY54, GmOLPb, CHS) in soybean plants. On the other hand, inoculation of NaCl-stressed soybean plants with Bacillus firmus SW5 promoted the growth and biomass yield, chlorophyll synthesis, nutrient uptake, gas exchange parameters, osmolytes levels, total phenolic and flavonoid contents, and antioxidant enzymes activities, in comparison with the plants treated with NaCl alone. Bacillus firmus SW5 inoculation also significantly reduced the IC50 values for both DPPH and β-carotene-linoleic acid assays and indicated higher antioxidant activities in salt-stressed plants. Furthermore, contents of H2O2 and MDA were alleviated in salinity-stressed soybean plants inoculated with Bacillus firmus SW5, in comparison with those in plants exposed to NaCl alone. The antioxidant enzyme-encoding genes and stress-related genes exhibited the highest expression levels in soybean plants inoculated with Bacillus firmus SW5 and treated with 80 mM NaCl. Taken together, our results demonstrate the crucial role of Bacillus firmus SW5 in ameliorating the adverse effects of high salinity on soybean growth and performance via altering the root system architecture and inducing the antioxidant defense systems and stress-responsive genes expression.

A mini-review of anti-hepatitis B virus activity of medicinal plants

ABSTRACT Medicinal plants are of undoubted value, as they have been used for centuries to treat various diseases and health disorders in almost every part of the world. In several studies, the use of medicinal plants was found effective in treatment of infectious and non-infectious diseases. The World Health Organization has been working for many years to identify all surviving medicinal plants on the earth. An important step has also been taken by the Natural Health Product Regulation of Canada for promotion and usages of natural products. At present, the rapidly growing population of the world is facing many challenges from various infectious diseases that are associated with hepatitis A, B and C virus, human immunodeficiency virus, influenza virus, dengue virus and new emerging viruses. Hepatitis B virus causes a severe and frequently transmittable disease of the liver. Millions of people worldwide suffer from hepatitis B virus (HBV) infection. The drugs available on the market for the treatment of hepatitis B are not sufficient and also cause side effects in patients suffering from HBV infection. The pharmaceutical companies are searching for suitable alternative and natural inhibitors of HBV. Therefore, it is important to explore and use plants as a source of new medicines to treat this infectious disease, because single plants contain a priceless pool of active ingredients which could help in the production of pharmaceutical-grade peptides or proteins. However, the knowledge of the antiviral activity of medicinal plants is still limited.

Exogenous application of nitric oxide and spermidine reduces the negative effects of salt stress on tomato

Due to increasing soil salinity, the world agricultural output is being threatened by the shrinking area of fertile land. In the present study, we explored the interactive roles of nitric oxide (NO; 100 μM) and spermidine (SP; 200 μM) in ameliorating the effects of salt stress (NaCl; 100 mM) in tomato (Solanum lycopersicum L. var. Five Star) seedlings. NaCl stress reduced shoot and root length, shoot and root fresh weight, shoot and root dry weight plant -1 and leaf area leaf -1. NaCl stress also suppressed the biosynthesis of photosynthetic pigments (Chlorophyll a and b) and increased proline (Pro) content, membrane damage and lipid peroxidation by inducing reactive oxygen species (H2O2 and O2• - ) generation in roots and leaves, as well as electrolyte leakage (EL) and malondialdehyde (MDA) accumulation in leaves. However, applying NO and/or SP increased the activities of catalase, peroxidase, superoxide dismutase, glutathione reductase and ascorbate peroxidase and increased photosynthetic pigment (chlorophyll a and b) and Pro accumulation, as well as reducing H2O2 and O2• - and MDA content and EL, under salt stress. When tomato plants were treated with NO and SP simultaneously, NO signaling was further enhanced, which was confirmed by the addition of cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; NO scavenger].

Mitigation of adverse effects of heat stress on Vicia faba by exogenous application of magnesium

The effects of magnesium (Mg) supplementation on the growth performance, oxidative damage, DNA damage, and photosynthetic pigment synthesis, as well as on the activity level of carbonic anhydrase (CA), ribulose-1,5-bisphosphate carboxylase (Rubisco), and antioxidant enzymes were studied in Vicia faba L. plants exposed to heat stress (HS) and non-heat-stress (non-HS) conditions. Seeds were grown in pots containing a 1:1 mixture of sand and peat, with Mg treatments. The treatments consisted of (i) 0 Mg and non-HS (ambient temperature; control); (ii) 50 mM Mg; (iii) HS (38 °C); and (iv) 50 mM Mg and HS (38 °C). HS was imposed by placing potted plants in an incubator at 38 °C for 48 h. Growth attributes, total chlorophyll (Total Chl), and CA, and Rubisco activity decreased in plants subjected to HS, whereas accumulation of organic solutes [proline (Pro) and glycine betaine (GB)]; superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity; DNA damage; electrolyte leakage (EL); and malondialdehyde (MDA) and hydrogen peroxide (H2O2) content all increased. Application of Mg, however, significantly enhanced further proline (Pro), glycinebetaine (GB), SOD, POD, and CAT activity, and decreased DNA damage, EL, and MDA and H2O2 concentrations. These results suggest that adequate supply of Mg is not only essential for plant growth and development, but also improves plant tolerance to HS by suppressing cellular damage induced by reactive oxygen species through the enhancement of the accumulation of Pro and GB, and the actions of antioxidant enzymes.

Fertilizers and Their Contaminants in Soils, Surface and Groundwater

The success of sustainable food production greatly relies on the widespread use of mineral fertilizers. However, the commercially available fertilizers are blended with a range of trace metals, which are introduced in to the soil along with the application of fertilizers. Given the rising environmental concern, the interest in eco-friendly organic inputs to the soils has grown manifold. The additions of recycled organic fertilizers to the soils have been proposed as a substantially beneficial input in place of inorganic fertilizers. However, the application of organic fertilizers may result in the heavy metal enrichment of soil and imbalanced nutrient availability. Additionally, according to one estimate, only about half of the applied fertilizers are being utilized by the plants while the remaining unutilized fertilizers could enter the soil surface and water bodies and may affect the environment adversely. The major environmental concern includes the eutrophication of fresh water bodies and enrichment of the soil with toxic heavy metals and radionuclides. In the present article, in addition to highlighting the consequences of large-scale fertilizer inputs on soil health, the impact on water bodies is also discussed.

Potential of exogenously sourced kinetin in protecting Solanum lycopersicum from NaCl-induced oxidative stress through up-regulation of the antioxidant system, ascorbate-glutathione cycle and glyoxalase system

The protective role of exogenously applied kinetin (10 μM KN, a cytokinin) against the adverse effects caused by NaCl-induced (150 mM) stress in Solanum lycopersicum was investigated. Application of KN significantly enhanced growth and biomass production of normally grown plants (non-stressed) and also mitigated the adverse effect of NaCl on stressed plants to a considerable extent. Among the examined parameters, chlorophyll and carotenoid contents, photosynthetic parameters, components of the antioxidant system (both enzymatic and non-enzymatic), osmotica accumulation, and mineral uptake exhibited a significant increase following the application of KN. Furthermore, KN application reduced the generation of reactive free radical hydrogen peroxide, coupled with a significant reduction in lipid peroxidation and an increase in membrane stability. The activities of antioxidant enzymes, and glyoxylase system were found to be promoted in plants exposed to NaCl, and the activities were further promoted by KN application, thereby protecting S. lycopersicum plants against NaCl-induced oxidative damage. Further strengthening of the antioxidant system in KN supplied plants was ascribed to regulation of ascorbate-glutathione cycle, phenols and flavonoids in them. The levels of proline and glycine betaine increased considerably in KN-treated plants, thereby maintaining relative water content. Moreover, exogenous KN application reduced the inhibitory effects of NaCl on K+ and Ca2+ uptake, which resulted in a considerable reduction in tissue Na+/K+ ratio.

Ascorbic acid improves the tolerance of wheat plants to lead toxicity

ABSTRACT Among the heavy metals (HMs), lead (Pb) is considered as a toxic HM which adversely affects growth and development of crop plants. The present experiment was aimed to investigate the potential role of ascorbic acid (ASC) in the reversal of Pb-inhibited nitrogen and sulfur assimilation enzymes activity and activity of photosynthesis enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and growth response in wheat plants. Wheat seedlings were subjected to 0 mM (control) and 0.2 mM and 0.6 mM of ASC with and without 2 mM of Pb. Plants treated with Pb exhibited the following reduced growth characteristics (root length, shoot length, root fresh weight (FW), shoot FW, root dry weight (DW) and shoot DW). A decrease was also observed in the activity of Rubisco and ATP sulfurylase (ATP-S), relative water content (RWC), accumulation of total chlorophyll (Total Chl) and content of nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg)] in Pb-treated plants. However, an increase in Chl degradation and in the activity of O-acetylserine(thiol)lyase (OAS-TL) and accumulation of cysteine (Cys), malondialdehyde (MDA) and hydrogen peroxide (H2O2) was observed in plants under Pb stress. On the contrary, exogenous application of ASC mitigated the Pb-toxicity-induced oxidative damage by enhancing the activities of antioxidant enzymes, such as superoxide dismutase, catalase and glutathione reductase. Improved activity of antioxidant enzymes suppressed the formation of MDA and H2O2, which was reflected in the form of improved growth characteristics. Moreover, ASC induced improvement in plants defense systems by reduced Chl degradation and improved the content of essential nutrients (N, P, K, Ca and Mg) and Cys, RWC and the activity of Rubisco, ATP-S, NR and OAS-TL.