BACKGROUND AND AIMS The water-transport capacity of leaf venation is positively related to the leaf-lamina area, because the number and diameter of vein-xylem conduits are controlled to match the lamina area. This study aimed to investigate how this co-ordinated relationship between the leaf-lamina area and vein-xylem characteristics is achieved by examining the midrib xylem of tobacco leaves. ...

abstract the critical period of weed control (cpwc) is a period in the crop growth cycle during which weeds must be controlled to prevent yield losses. in order to determine the critical period of weed control (cpwc) of corn in hamedan, an experiment was conducted in 2007 at agricultural research station of bu-ali sina university of hamedan. the experiment was carried out as a randomized comple...

Understanding how tropical trees will respond to extreme temperatures and drought is essential to predict how future increases in the severity, frequency and duration of extreme climatic events will affect tropical systems. In this study, we investigated leaf thermotolerance by quantifying the temperatures that resulted in a 50 % decrease in photosystem II function (T50) in experimentally grown...

We studied inherent variation in final leaf size among four Poa spp. that live at different elevations. The average final length of leaf 7 of the main stem of the smallest species (Poa alpina) was only one-half that of the largest species (Poa trivialis); it was correlated with leaf elongation rate, but not with the duration of leaf elongation. A faster rate of leaf elongation rate was associat...

To elucidate climate-driven changes in leaf-out phenology and their implications for species invasions, we observed and experimentally manipulated leaf out of invasive and native woody plants in Concord, MA, USA. Using observations collected by Henry David Thoreau (1852-1860) and our own observations (2009-2013), we analyzed changes in leaf-out timing and sensitivity to temperature for 43 woody...

The design of grating-based instruments to handle and condition coherent ultrafast pulses in the extreme-ultraviolet is discussed. The main application of such instruments is the monochromatization of high-order laser harmonics and free-electron-laser pulses in the femtosecond time scale. Broad-band monochromators require the use of diffraction gratings at grazing incidence. A grating can be us...

Spring wheat cv. Minaret was grown under three carbon dioxide (C02) and two ozone (O3) concentrations from seedling emergence to maturity in open-top chambers. Under elevated CO2 concentrations, the green leaf area index of the main shoot was increased, largely due to an increase in green leaf area duration. Biomass increased linearly in response to increasing CO2 (ambient, 550 and 680 ppm). At...

In this study, the differences in reactive oxygen species (ROS) generation and abscisic acid (ABA) accumulation in senescing leaves were investigated by early-senescence-leaf (esl) mutant and its wild type, to clarify the relationship among ABA levels, ROS generation, and NADPH oxidase (Nox) in senescing leaves of rice (Oryza sativa). The temporal expression levels of OsNox isoforms in senescin...

BACKGROUND AND AIMS In crops other than sugarcane there is good evidence that the size and activity of carbon sinks influence source activity via sugar-related regulation of the enzymes of photosynthesis, an effect that is partly mediated through coarse regulation of gene expression. METHODS In the current study, leaf shading treatments were used to perturb the source-sink balance in 12-month...