26 research outputs found
Effects of temperature at constant air dew point on leaf carboxylation efficiency and CO 2 compensation point of different leaf types
The effect of temperature on photosynthesis at constant water-vapor pressure in the air was investigated using two sclerophyll species, Arbutus unedo and Quercus suber , and one mesophytic species, Spinacia oleracea . Photosynthesis and transpiration were measured over a range of temperatures, 20–39° C. The external concentration of CO 2 was varied from 340 μbar to near CO 2 compensation. The initial slope (carboxylation efficiency, CE) of the photosynthetic response to intercellular CO 2 concentration, the CO 2 compensation point (Γ), and the extrapolated rate of CO 2 released into CO 2 -free air ( R i ) were calculated. At an external CO 2 concentration of 320–340 μbar CO 2 , photosynthesis decreased with temperature in all species. The effect of temperature on Γ was similar in all species. While CE in S. oleracea changed little with temperature, CE decreased by 50% in Q. suber as temperature increased from 25 to 34° C. Arbutus unedo also exhibited a decrease in CE at higher temperatures but not as marked as Q. suber . The absolut value of R i increased with temperature in S. oleracea , while changing little or decreasing in the sclerophylls. Variations in Γ and R i of the sclerophyll species are not consistent with greater increase of respiration with temperature in the light in these species compared with S. oleracea .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47470/1/425_2004_Article_BF00397389.pd
The influence of nitrogen supply during growth on the inhibition of gas exchange and visible damage to leaves by NO2
Competitivity of the common-bean plant relative to the weed alexandergrass [Brachiaria plantaginea (link) hitch.]
The Measurement of Focal Diurnal Variation in the Femoral Articular Cartilage of the Knee
Competition effects with mixed stands of wheat and kochia (Kochia scoparia) biotypes resistant and susceptible to acetolactase synthase inhibitor herbicides
Competition between Artemisia frigida and Cleistogenes squarrosa under different clipping intensities in replacement series mixtures at different nitrogen levels
Dynamics of competition between wild oats (Avena fatua L.) and winter cereals
This study examined the effects of competition on the growth of Avena fatua, winter wheat and winter barley. Plants were sampled at frequent intervals from replacement series experiments at two contrasting sites in the U.K. A. fatua was much slower to establish than the two cereals, but thereafter exhibited a faster rate of growth. In monoculture, it took a considerable time for A. fatua to reach a size equal to that of the cereals, but by the end of the experiments it was the largest of the three species. The change-over from cereal dominance in mixtures to A. fatua dominance was rapid, and in three cases coincided with cereal flag leaf emergence. In the fourth case, it appeared to coincide with the start of canopy height extension. At one site the order of competitiveness at anthesis was A. fatua = barley > wheat, and at the other site the order was A. fatua > wheat > barley. In order to explain and predict differences between years and sites, more studies are required on morphological development in relation to abiotic variables