Effects of Drought Stress on Photosynthesis Factors in Wheat Genotypes during Anthesis

Drought is one of most important environmental factors inhibiting photosynthesis and decreasing growth and productivity of plants. The sensitivity of crop plants such as wheat to soil drought is particularly serious during reproductive phase is extremely sensitive to plant water status. The aim of this work was to study the effects of drought stress on photosynthesis, photosynthetic pigments, soluble proteins, a-tocopherol and abscisic acid content in six wheat genotypes, two tolerant (Daric and 92 Zhong), two moderately tolerant (Sabalan and DH-2049-3) and two sensitive (Shark and Tevee’s’). Total chlorophyll content, relative water content and chlorophyll a/b ratio decreased after long-time drought stress, that decrease in sensitive genotypes was higher than others. Net photosynthesis and stomatal conductance decreased significantly (P < 0.05) in flag leaves of our genotypes under drought stress after pollination, that decrease in sensitive genotypes was higher, too. Abscisic acid content, soluble protein content and a-tocopherol increased under drought stress, that increase in tolerant genotypes was higher. There was a significant negative correlation (P < 0.05) between photosynthesis factors and abscisic acid content in flag leaves of all genotypes. It can be concluded that Daric and 92 Zhong had a better photosynthesis factors compared to other genotypes and showed a higher capacity to tolerate drought stress

Effects of salinity on antioxidant system in four grape (Vitis vinifera L.) genotypes

Salinity is a major environmental stress that restricts plants growth and production. Grapes are classified as moderately sensitive to salinity. The aim of this work was to investigate the salinity effects on lipid peroxidation level, antioxidant compounds and anti-oxidative enzymes activities and photosynthetic pigment contents in four grape genotypes that are commonly grown in the region around Urmia salt lake. Malondialdehyde content and protective enzymes activities in roots and leaves of four genotypes increased significantly (P &lt; 0.05) under salinity. 'Chawga' showed lower and higher increases in malondialdehyde content and enzymes activities, respectively. Salinity had an obvious effect on the accumulation of total phenolics content and induced phenylalanine ammonia-lyase enzyme activity in all genotypes. There were significant positive correlations (P &lt; 0.01, r2= 0.838) between anti-oxidative enzyme activities, total phenolics content and phenylalanine ammonia-lyase activity in the leaves of all genotypes. Chlorophyll a, b contents in leaves of all genotypes were reduced and carotenoid content increased significantly (P &lt; 0.05) under salinity. 'Chawga' showed a lower decrease in chlorophyll content and a higher increase in carotenoid content than others. It seems that 'Chawga' had a better antioxidant system compared to other genotypes and showed a higher capacity to tolerate salinity.

Effects of salinity on potassium absorption and expression of K+transporter genes at different concentrations of potassium in Grape (Vitis vinifera L.)

Grapevine is classified as a moderately sensitive plant to salinity. Hydroponically three grape genotypes (Vitis vinifera L.) were treated with different concentrations of KCl (0.1, 0.3, 0.5, 1, 5, 10 mM KCl) and NaCl (0, 25, 50,100 mM NaCl). Cl- and Na+ contents were significantly increased in different plant organs of all the genotypes under salinity. In this study, sensitive ('GhezelUzum'), tolerant ('Gharashani') and semi-resistant ('Chawga') grape genotypes were selected based on screening experiments under salinity. 'Gharashani' accumulated higher Na+ and Cl- in roots compared to the sensitive one. 'Chawga' accumulated high K+ similar to Na+ in root and shoot even at high salinity. Km calculation for K+ and Na+ uptake in root and shoot of 'Chawga' showed that K+ and Na+ compete to enter the plant through roots. Two KUP/KT/HAK-type potassium transporters are expressed highly in the grapevine during stress. VvK1.1 could play a major role in K+ loading into grape tissues. The expression of VvKUP1 and VvKUP2 transporters and VvK1.1 channel in roots of 'Chawga' genotype increased significantly (P &lt; 0.05) at different KCl concentrations under salinity stress. Our results showed a significant difference between tolerant and sensitive genotypes and highlighted a strong relationship between the accumulation of specific transcripts and the degree of salinity tolerance

Fabrication of Iron Aluminide Coatings (Fe3Al and FeAl3) on Steel Substrate by Self-Propagating High Temperature Synthesis (SHS) Process

Iron aluminides (Fe3Al and FeAl3) coatings were fabricated on a steel substrate by self-propagating high temperature synthesis (SHS) method. Raw materials, Fe and Al powders, were mixed at two different stoichiometry ratios (3:1 and 1:3). The mixtures and the substrate were placed in a furnace at 950 °C to ignite the SHS process. Coating phases were investigated using X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS). The microstructure of the coatings was analyzed with optical microscopy (OM) and scanning electron microscopy (SEM). The results confirmed that it is possible to produce Fe3Al and FeAl3 coatings on steel substrate using SHS method. In addition, the results show that the coatings were composed of two different phases and their microstructures were non-porous and dense. Wear resistance of the coatings were higher than that of the substrate

Magnetic interference pattern in planar SNS Josephson junctions

We study the Josephson current through a ballistic normal metal layer of thickness $D$ on which two superconducting electrodes are deposited within a distance $L$ of each other. In the presence of an ({\it in-layer}) magnetic field we find that the oscillations of the critical current $I_c(\Phi)$ with the magnetic flux $\Phi$ are significantly different from an ordinary magnetic interference pattern. Depending on the ratio $L/D$ and temperature, $I_c(\Phi)$-oscillations can have a period smaller than flux quantum $\Phi_0$, nonzero minima and damping rate much smaller than $1/\Phi$. Similar anomalous magnetic interference pattern was recently observed experimentally.Comment: 6 pages, 4 figures, Accepted by Phys. Rev.

Nonsinusoidal current-phase relations and the 0−π0-\pi transition in diffusive ferromagnetic Josephson junctions

We study the effect of the interfacial transparency on the Josephson current in a diffusive ferromagnetic contact between two superconductors. In contrast to the cases of the fully transparent and the low-transparency interfaces, the current-phase relation is shown to be nonsinusoidal for a finite transparency. It is demonstrated that even for the nearly fully transparent interfaces the small corrections due to weak interfacial disorders contribute a small second-harmonic component in the current-phase relation. For a certain thicknesses of the ferromagnetic contact and the exchange field this can lead to a tiny minimum supercurrent at the crossover between 0 and $\pi$ states of the junction. Our theory has a satisfactory agreement with the recent experiments in which a finite supercurrent was observed at the transition temperature. We further explain the possibility for observation of a large residual supercurrent if the interfaces have an intermediate transparency.Comment: 7 pages, 4 figure

Prevalence of Cannabis Lifetime Use in Iranian High School and College Students: A Systematic Review, Meta-Analyses,and Meta-Regression

Cannabis is the most widely used substance in the world. This study aimed to estimate the prevalence of cannabis lifetime use (CLU) in high school and college students of Iran and also to determine factors related to changes in prevalence. A systematic review of literature on cannabis use in Iran was conducted according to MOOSE guideline. Domestic scientific databases, PubMed/Medline, ISI Web of Knowledge, and Google Scholar, relevant reference lists, and relevant journals were searched up to April, 2014. Prevalences were calculated using the variance stabilizing double arcsine transformation and confidence intervals (CIs) estimated using the Wilson method. Heterogeneity was assessed by Cochran's Q statistic and I-2 index and causes of heterogeneity were evaluated using meta-regression model. In electronic database search, 4,000 citations were retrieved, producing a total of 33 studies. CLU was reported with a random effects pooled prevalence of 4.0 (95 CI = 3.0 to 5.0). In subgroups of high school and college students, prevalences were 5.0 (95 CI = 3.0 to -7.0) and 2.0 (95 CI = 2.0 to -3.0), respectively. Meta-regression model indicated that prevalence is higher in college students (beta = 0.089, p < .001), male gender (beta = 0.017, p < .001), and is lower in studies with sampling versus census studies (beta = -0.096, p < .001). This study reported that prevalence of CLU in Iranian students are lower than industrialized countries. In addition, gender, level of education, and methods of sampling are highly associated with changes in the prevalence of CLU across provinces

Combinations of Plant Water-Stress and Neonicotinoids Can Lead to Secondary Outbreaks of Banks Grass Mite (Oligonychus Pratensis Banks)

Spider mites, a cosmopolitan pest of agricultural and landscape plants, thrive under hot and dry conditions, which could become more frequent and extreme due to climate change. Recent work has shown that neonicotinoids, a widely used class of systemic insecticides that have come under scrutiny for non-target effects, can elevate spider mite populations. Both water-stress and neonicotinoids independently alter plant resistance against herbivores. Yet, the interaction between these two factors on spider mites is unclear, particularly for Banks grass mite (Oligonychus pratensis; BGM). We conducted a field study to examine the effects of water-stress (optimal irrigation = 100% estimated evapotranspiration (ET) replacement, water stress = 25% of the water provided to optimally irrigated plants) and neonicotinoid seed treatments (control, clothianidin, thiamethoxam) on resident mite populations in corn (Zea mays, hybrid KSC7112). Our field study was followed by a manipulative field cage study and a parallel greenhouse study, where we tested the effects of water-stress and neonicotinoids on BGM and plant responses. We found that water-stress and clothianidin consistently increased BGM densities, while thiamethoxam-treated plants only had this effect when plants were mature. Water-stress and BGM herbivory had a greater effect on plant defenses than neonicotinoids alone, and the combination of BGM herbivory with the two abiotic factors increased the concentration of total soluble proteins. These results suggest that spider mite outbreaks by combinations of changes in plant defenses and protein concentration are triggered by water-stress and neonicotinoids, but the severity of the infestations varies depending on the insecticide active ingredient

The Physiology and Proteomics of Drought Tolerance in Maize: Early Stomatal Closure as a Cause of Lower Tolerance to Short-Term Dehydration?

Understanding the response of a crop to drought is the first step in the breeding of tolerant genotypes. In our study, two maize (Zea mays L.) genotypes with contrasting sensitivity to dehydration were subjected to moderate drought conditions. The subsequent analysis of their physiological parameters revealed a decreased stomatal conductance accompanied by a slighter decrease in the relative water content in the sensitive genotype. In contrast, the tolerant genotype maintained open stomata and active photosynthesis, even under dehydration conditions. Drought-induced changes in the leaf proteome were analyzed by two independent approaches, 2D gel electrophoresis and iTRAQ analysis, which provided compatible but only partially overlapping results. Drought caused the up-regulation of protective and stress-related proteins (mainly chaperones and dehydrins) in both genotypes. The differences in the levels of various detoxification proteins corresponded well with the observed changes in the activities of antioxidant enzymes. The number and levels of up-regulated protective proteins were generally lower in the sensitive genotype, implying a reduced level of proteosynthesis, which was also indicated by specific changes in the components of the translation machinery. Based on these results, we propose that the hypersensitive early stomatal closure in the sensitive genotype leads to the inhibition of photosynthesis and, subsequently, to a less efficient synthesis of the protective/detoxification proteins that are associated with drought tolerance