Soil warming enhances the hidden shift of elemental stoichiometry by elevated CO₂ in wheat

Increase in atmospheric CO(2) concentration ([CO(2)]) and associated soil warming along with global climate change are expected to have large impacts on grain mineral nutrition in wheat. The effects of CO(2) elevation (700 μmol l(−1)) and soil warming (+2.4 °C) on K, Ca and Mg concentrations in the xylem sap and their partitioning in different organs of wheat plant during grain filling were investigated. Results showed that the combination of elevated [CO(2)] and soil warming improved wheat grain yield, but decreased plant K, Ca and Mg accumulation and their concentrations in the leaves, stems, roots and grains. The reduced grain mineral concentration was attributed to the lowered mineral uptake as exemplified by both the decreased stomatal conductance and mineral concentration in the xylem sap. These findings suggest that future higher atmospheric [CO(2)] and warmer soil conditions may decrease the dietary availability of minerals from wheat crops. Breeding wheat cultivars possessing higher ability of mineral uptake at reduced xylem flux in exposure to climate change should be a target

Asymptotic Stability Results for Nonlinear Fractional Difference Equations

We present some results for the asymptotic stability of solutions for nonlinear fractional difference equations involvingRiemann-Liouville-likedifference operator. The results are obtained by using Krasnoselskii's fixed point theorem and discrete Arzela-Ascoli's theorem. Three examples are also provided to illustrate our main results

Drought Tolerance and Perennial Weed Management

The aim of this study was to investigate the effect of controlled soil water deficits on sprouting and shoot growth of Canada thistle, coltsfoots and quackgrass. A gradient of soil water contents was created by establishing different densities of barley. The plants were harvested 14 days after watering was stopped. On Canada thistle and coltsfoots, relative water content (RWC) in leaves was measured prior to harvest and biomass of all weed shoots were recorded at harvest. In terms of shoot biomass and leaf RWC quackgrass was drought tolerant while coltsfoot was drought sensitive and Canada thistle was between the two. The barley cover crop could have had a competitive effect upon the growth of the weeds; the effect, however, was not detrimental compared to the drought effect, because relationships between initial height and the final height of coltsfoot and Canada thistle were not different among barley densities. The results suggest that the shooting from subterranean parts of broadleaf perennial weeds can to some extent be impeded by reducing soil water availability. However, the use of reduced soil water content can be challenging in fields in humid temperate regions