Do genotypes ameliorate herbivory stress through silicon amendments differently? A case study of wheat.

Agricultural productivity relies on plant resistance to insect pests, with silicon (Si) being increasingly recognized as an important anti-herbivore defense. However, the processes by which Si works to counteract the effects of insect injury are not completely understood. The role of Si in mitigating the adverse effects of herbivory has been mostly studied at the species level in various crops, ignoring the sensitivity and variability at the genotypic level. Understanding such variation across genotypes is important because Si-derived benefits are associated with the amount of Si accumulated in the plant. Therefore, the present investigation was pursued to study the effect of different Si concentrations (0, 125, and 250 mg L⁻1) on Si accumulation and plant growth using two wheat genotypes (WW-101 and SW-2) under grasshopper herbivory for 48 h. The higher Si absorption increased the concentration of leaf chlorophyll, carotenoids, soluble sugars, and proteins. Silicon application at higher concentrations increased the dry weight, antioxidant enzyme activity, total phenolics, flavonoids and shoot Si concentration, whereas it decreased the electrolyte leakage, hydrogen peroxide (H2O2) and malonaldehyde (MDA) levels, thereby preventing leaf damage. We infer that the higher Si concentration alleviates the adverse effects of herbivory in wheat by improving the accumulation of secondary metabolites and enhancing the antioxidant defense system. The effects were pronounced in the genotype 'WW-101' compared to 'SW-2' for most of the studied traits, indicating overall stress response to be genotype-dependent. Thus, Si acquisition efficiency of genotypes should be considered while developing efficient crop management strategies.

Elucidating the role of silicon in drought stress tolerance in plants.

Predicted changes in climate, with more severe droughts and more extreme weather variability, are gaining considerable attention from stakeholders because of the already stressed and seriously challenging agricultural ecosystems of the contemporary world. One of the greatest challenges faced by these unique ecosystems due to climate change is drought stress, which affects plant growth, development and metabolic processes, thus reducing production, yield, and quality of crop plants. Plants counter this stress by employing complex mechanisms through a series of physiological, cellular, and molecular processes. Among the myriad of stress tolerance mechanisms, the positive effects of Si on water status of plants have been widely appreciated. Here, we review the potential of Si supplementation in alleviating drought stress and highlight the imported mechanisms involved in Si mediated reduction of drought stress in plants. Si fertilization not only enhances the photosynthetic pigments, growth, biomass, antioxidant enzymes, gene expression, osmolyte concentrations and nutrient uptake but also improves crop production, yield and grain quality during drought stress. In addition, it provides insights on important mechanisms involved in the modification of gas exchange attributes, gene modification, nutritional homeostasis, control synthesis of compatible solutes, osmotic adjustment and stimulation of phytohormone biosynthesis and antioxidant enzymes under drought stress. We also highlight knowledge gaps and future research prospects to understand Si mediated role in alleviating drought stress.

Economic growth, energy consumption, and environmental quality nexus in Turkey: Evidence from simultaneous equation models.

The present research article uses simultaneous equation modelling approach to investigate the three-way linkages between economic growth, energy consumption, and environmental quality in Turkey for the 1970 to 2014 period. Further, the study uses physical capital stock, labour force, manufacturing value added, trade openness, credit to private sector, and urbanisation as control variables. The paper employs generalised method of moments (GMM) technique that ensures consistent and efficient estimates of the long-run relationship. The econometric approach controls for nonstationarity, endogeneity, cross-error correlation, and heteroscedasticity problems. Further, robustness of the results is checked by using three-stage least squares (3SLS) estimator. The statistical results of the paper support the existence of bidirectional causality between energy consumption and economic growth, CO2 emissions and economic growth, and CO2 emissions and energy consumption. Moreover, the results indicate existence of a monotonically increasing relationship between CO2 emissions and economic growth implying non-existence of Environmental Kuznets Curve hypothesis in Turkey during the sample period. The findings of the present study are of particular interest to policymakers as they help pursue economic policies to achieve sustainable development.

Association between copper excess, zinc deficiency, and TP53 mutations in esophageal squamous cell carcinoma from Kashmir Valley, India--a high risk area.

Trace element deficiency or excess is implicated in the development or progression in some cancers. Here we report the elevated level of copper and low level of zinc in the plasma of esophageal cancer patients in Kashmir India--a high incidence area. The average level of copper was significantly higher (P < 0.0001) for patients than for controls, with a mean concentration of 169 microg/dl and 149 microg/dl for patients and controls, respectively. The control group consisted of 55 healthy individuals matched for age, sex, and place of residence of the patients. In contrast, the average level of zinc in patients was significantly lower than in controls (P < 0.0001), with a mean concentration of 86.8 microg/dl and 96.1 microg/dl for patients and controls, respectively. The levels of both copper and zinc showed significant differences based on gender and age in patients as compared to controls. Similarly, smokers depicted a significant increase in serum copper (N = 39, P = 0.002) and a decrease in serum zinc approaching level of significance in the patient group as compared to controls. The copper and zinc levels were significantly altered in patients (N = 40) when compared to controls as a function of snuff consumption. The differences in the levels of copper and zinc showed significant association with the consumption of local salted tea up to 1,500 ml per day, but the changes were insignificant beyond that. Patients with poorly differentiated tumors (N = 7) had a higher copper concentration than those with moderately or well-differentiated tumors (P < 0.0001). To validate the general notion that imbalance in copper and zinc levels may lead to higher prevalence of TP53 mutations, we compared the 3 variables, and no association was found between copper concentration and TP53 mutation status; but patients with TP53 mutant tumor had lower zinc levels than those with no mutation. In conclusion, our results point toward a role of the trace element imbalance in the esophageal tumorigenesis in high-risk Kashmiri population exposed to a range of nitroso compounds or their precursors. Further prospective cohort studies are warranted to determine whether change in the plasma zinc and copper homeostasis may represent an independent risk factor for this malignancy as well as a possible target for preventive intervention.

Studies on Association Between Copper Excess, Zinc Deficiency and TP53 Mutations in Esophageal Squamous Cell Carcinoma From Kashmir Valley, India-A High Risk Area.

Trace element deficiency or excess is implicated in the development or progression in some cancers. Here we report the elevated levels of copper and low level of zinc in the plasma of esophageal cancer patients in Kashmir India- a high incidence area. The average level of copper was significantly higher for patients than for controls (p<0.0001) with a mean concentration of 169 µg/dl and 149 µg/dl for patients and controls, respectively. In contrast, the average level of zinc in patients was significantly lower than in controls (p<0.0001) with a mean concentration of 86.8 µg/dl and 96.1 µg/dl for patients and controls, respectively. No significant difference in copper and zinc levels was observed for different age groups in controls or patients. For controls, the level of copper was not significantly different in males and females (median: 155 µg/dl for males and 144 µg/dl for females, p=0.10), but we observed a higher level of zinc in females (median: 90.5 µg/dl for males and 101 µg/dl for females, p=0.03). Copper or zinc concentrations were not significantly associated with gender, tumor site, green tea with salt (nun chai) consumption, smoking habits or snuff in cases. Patients with poorly differentiated tumors had a higher copper concentration than those with moderately or well-differentiated tumors (p<0.0001). No association was found between copper concentration and TP53 mutation status but patients with TP53 mutant tumor had lower zinc levels than those with no mutation. Our results point towards a role of the trace element imbalance in the esophageal tumorigenesis in high risk Kashmiri population exposed to a range of nitroso compounds or their precursors. Further prospective cohort studies are warranted to determine whether change in the plasma zinc and copper homeostasis may represent an independent risk factor for this malignancy as well as possible target for preventive intervention.