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Productivity of glasshouse crops is strongly limited by lightreceipt, and efficient interception and use of light in photosynthesisis correspondingly important. Mature row crop canopies of cucumberand tomato intercepted about 76% of the light incident on theirupper surfaces; about 18% was lost through gaps between therows. Light transmitted through the entire depth of the canopywas reflected back by white plastic on the ground, so that thelower surface of the canopy received approximately 13% of thelight incident on the upper surface. The light flux incidenton the sides of these canopies (c. 2m tall and 6m x 16m in area)amounted to some 2030% of that incident on the uppersurface. About 32% of daylight falling on the glasshouse (c.9m x 18m in area) was intercepted by the glasshouse structureand glazing; of the 68% entering the house, some fell on headlandsoccupying 35% of the glasshouse area. The loss of light to headlands,and the gain from canopy side-lighting, would be relativelysmaller for larger glasshouses. At near-ambient CO2 concentrations, net photosynthetic ratesof the cucumber canopy were comparable to those of closed canopiesof other glasshouse and field crops which have maximum lightconversion efficiencies of 58µg CO2 J1 at50200 W m2 incident light flux density. Efficiencydecreases only slightly with stronger light. Glasshouse cropswith CO2 enrichment to 1200 vpm achieve conversion efficienciesof 710µg CO2 J1. Efficiencies of utilizationof intercepted light, on an energy basis, reach 610%in various field and glasshouse crops with near-ambient CO2,and reached an exceptional 11% for the cucumber canopy. Glasshousecrops with CO2 enrichment achieve maximum efficiency of lightenergy utilization between 12% and 13%. Key words: Glasshouse cucumber and tomato, light interception and utilization, photosynthetic efficiency, row crops 相似文献
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Epidermal strips from either well-watered or water-stressedplants of Commelina communis L. were subjected to a range ofABA concentrations (106103 mol m3)in the presence (330 parts 106 in air) or virtual absence(3 parts 106 in air) of CO2. The stomatal response toCO2 was greater in epidermis from water-stressed plants, althoughthere was a distinct CO2 response in epidermis from well-wateredplants. Additions of ABA via the incubation medium had littleeffect on the relative CO2 response. Stomata responded to ABAboth in the presence and virtual absence of CO2, but the relativeresponse to ABA was greatest in the high CO2 treatment. Whenwell-watered plants were sprayed with a 101 mol m3ABA solution 1 d prior to use, the stomatal response of detachedepidermis to both CO2 and ABA was very similar to that of epidermisdetached from water-stressed leaves. It is hypothesized thata prolonged exposure to ABA is necessary before there is anymodification of the CO2 response of stomata. 相似文献
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The breeder's equation, which predicts evolutionary change when a phenotypic covariance exists between a heritable trait and fitness, has provided a key conceptual framework for studies of adaptive microevolution in nature. However, its application requires strong assumptions to be made about the causation of fitness variation. In its univariate form, the breeder's equation assumes that the trait of interest is not correlated with other traits having causal effects on fitness. In its multivariate form, the validity of predicted change rests on the assumption that all such correlated traits have been measured and incorporated into the analysis. Here, we (i) highlight why these assumptions are likely to be seriously violated in studies of natural, rather than artificial, selection and (ii) advocate wider use of the Robertson–Price identity as a more robust, and less assumption‐laden, alternative to the breeder's equation for applications in evolutionary ecology. 相似文献
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DAVID T. ZANATTA CHRIS C. WILSON 《Biological journal of the Linnean Society. Linnean Society of London》2011,102(3):669-685
The macrogeographic dispersal of unionoid mussels is largely dependent on movement by their host fish. The snuffbox mussel Epioblasma triquetra (Unionoida) and other congeners use a novel trapping behaviour to parasitize potential host fish with their larvae (glochidia). Common logperch (Percina caprodes) trapped by E. triquetra survive the trapping behaviour, whereas other darter species (Etheostoma and Percina) do not, thus, making the P. caprodes–E. triquetra relationship a good candidate system for a coevolutionary study. We hypothesized that the geographic genetic structure of E. triquetra should closely match that of its host, albeit with greater interpopulation divergences as a result of its dependency on the host for dispersal. Mantel tests of parallel pairwise matrices of population divergence (Jost's D) and genetic assignment tests based on microsatellite DNA data showed that the genetic population structures of both species were broadly, but not perfectly, congruent. Therefore, it appears that P. caprodes are not solely responsible for the genetic population structure observed for snuffbox and may not necessarily be the mussel's only host across its entire range. This suggests the potential for a geographic mosaic for coevolution in unionoids and darters. The findings of the present study reinforce the need for a joint study and conservation of unionoids and host fish aiming to protect these coevolved taxa. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 669–685. 相似文献
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JAVIER GUTIÉRREZ ILLÁN DAVID GUTIÉRREZ SONIA B. DÍEZ ROBERT J. WILSON 《Ecological Entomology》2012,37(2):134-144
1. Impacts of global change on the distribution, abundance, and phenology of species have been widely documented. In particular, recent climate change has led to widespread changes in animal and plant seasonality, leading to debate about its potential to cause phenological mismatches among interacting taxa. 2. In mountainous regions, populations of many species show pronounced phenological gradients over short geographic distances, presenting the opportunity to test for effects of climate on phenology, independent of variation in confounding factors such as photoperiod. 3. Here we show for 32 butterfly species sampled for five years over a 1700 m gradient (560–2260 m) in a Mediterranean mountain range that, on average, annual flight period is delayed with elevation by 15–22 days per kilometre. Species mainly occurring at low elevations in the region, and to some extent those flying earlier in the year, showed phenological delays of 23–36 days per kilometre, whereas the flight periods of species that occupy high elevations, or fly in late summer, were consistently more synchronised over the elevation gradient. 4. Elevational patterns in phenology appear to reflect a narrowing phenological window of opportunity for larval and adult butterfly activity of high elevation and late‐flying species. 5. Here, we speculate as to the causes of these patterns, and the consequences for our ability to predict species responses to climate change. Our results raise questions about the use of space–time substitutions in predicting phenological responses to climate change, since traits relating to flight period and environmental associations may influence the capacity of species to adapt to changing climates. 相似文献
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MARK A. WILSON TIMOTHY J. PALMER THOMAS E. GUENSBURG CHRISTOPHER D. FINTON LEWIS E. KAUFMAN 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1992,25(1):19-34
The Kanosh Shale (Upper Arenig, Lower Ordovician) of west-central Utah. USA. contains abundant carbonate hardgrounds and one of the earliest diverse hardground communities. The hardgrounds were formed through a combination of processes including the development of early digenetic nodules in clay sediments which were exhumed and concentrated as lags by storms. These cobble deposits. together with plentiful biogenic metrical. were cemented by inorganically precipitated calcite on the sea floor. forming intraformational conglomerate hardgrounds. Echinoderms may have -played a critical role in the development of hardground faunas since their disarticulated calcite ossicles were rapidly cemented by syntaxial overgrowths. forming additional cobbles and hardgrounds. The echinoderms thus may have taphonomically facilitated the development of some of the hard substrates they required. A significant portion of the hardground cements may have been derived from the early dissolution of aragonitic mollusk shells. Kanosh hardground species include the earliest bryozoans recorded on hardgrounds and large numbers of stemmed echinoderms. primarily rhipidocystid cocrinoids. Bryozoans and echinoderms covered nearly equal areas of the hardground surfaces. and there was a distinct polarization between species which preferred the upper. exposed portions of the hardgrounds and others which were most common on undercut. overhang surfaces. The Kanosh Shale hardground fossils combine elements of Late Cambrian assemblages and Middle Ordovician faunas, thus confirming predicted trends in hardground community evolution. especially the replacement of cocrinoids by bryozoans and. to a lesser extent, by other stemmed echinoderms, especially crinoids. The Kanosh community marks the transition from the Cambrian Fauna to The Paleozoic Fauna in The hardground ecosystem. *Carbonate hardgrounds, aragonite dissolution, calcite cement, Echinodermara, Trepostomata, Nicholsonclla. Dianulites. Porifpra. taphonomic facilitation, Utah. Pogonip Group, Kanosh Shale. Ordovician. 相似文献
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