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81.
Sterling J. Nesbitt Alan H. Turner Michelle Spaulding Jack L. Conrad Mark A. Norell 《Journal of morphology》2009,270(7):856-879
The furcula is a structure formed by the midline fusion of the clavicles. This is the element which is unique to theropods and is important for understanding the link between birds and other theropods. New specimens from basal theropods suggest that the furcula appeared very early in theropod history. We review furcula development, function, and morphology, as well as the anatomical terminology applied to it. Furcular morphology is highly variable in crown‐group avians but is rather conserved among nonavian theropods. Here we review, or describe for the first time, the furculae in many nonavian theropods. Furculae occur in nearly all major clades of theropods, as shown by new theropod specimens from the Early Cretaceous of China and a close inspection of previously collected specimens. Informative phylogenetic characters pertaining to the furcula occur throughout Theropoda, though care should betake to consider taphonomic effects when describing furcular morphology. J. Morphol., 2009. © 2009 Wiley‐Liss, Inc. 相似文献
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Contradictory results have been reported for the effects of triazoles on abscisic acid (ABA) levels in plants. Paclobutrazol reduced the height, fresh weight, and ABA levels of wheat seedlings. The magnitude of the inhibitory effect of paclobutrazol on ABA levels was dependent on the length of time after application. ABA levels in plants as determined by gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) were reduced by 50–60% 2 days after soil application. A further 15% reduction occurred by the seventh day after treatment. ABA level analyses began at the time of treatment with 4-day-old seedlings and continued until 21 days after treatment when only a 20% reduction was detected. These determinations using GC-SIM-MS should increase the understanding of triazole effects on ABA levels. 相似文献
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The highly pathogenic Phytophthora ramorum, causal organism of sudden oak death (SOD), is established in forests of the Pacific Northwest (USA) and is threatening invasion
of other regions. Given the breadth of its host range, with dozens of asymptomatic ornamental hosts and with oaks, Quercus spp., in the red oak (Erythrobalanus) subgenus particularly susceptible, we investigated the consequences of its invasion and establishment in oak-dominated deciduous
forests of the eastern USA. We evaluated the nature and extent of pathogen invasion using vegetation assessments coupled with
growth simulations. The woody plant community was assessed in three strata (upper, mid- and lower) and was used to characterize
forest composition and structure. Using the Forest Vegetation Simulator (FVS), we then projected woody vegetation growth 50 years
into the future with and without the effects of SOD. In forest simulations lacking pathogen invasion, little change in composition
or structure is forecasted. Both red oaks and white oaks (subgenus Leucobalanus) increase slightly but significantly over the length of the simulation. In contrast, in SOD-affected forests our projections
predict a significant loss of red oaks within 10 years of pathogen invasion. Basal area of white oaks and non-oaks is expected
to increase more so in the absence of red oaks. The loss of red oaks to pathogen infection will result in greater increases
in red maple, Acer rubrum, and yellow poplar, Liriodendron
tulipifera, than in forests free of SOD. Loss of red oak represents a significant loss of hard mast, with potentially devastating consequences
for wildlife. Red oak loss will also affect decomposition rates, nutrient cycling, forest structure, and timber values, with
consequences for forest health and sustainability. 相似文献
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