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41.
采用红外气体分析仪,于2008年10月17-19日连续3个昼夜原位监测了荷木的树干CO_2释放通量、树干温度、木质部液流密度和CO_2浓度.结果表明:树干CO_2释放通量(EA)日变化呈S形曲线,不同径级间差异显著.EA与树干温度呈显著幂函数关系(0.24Abstract: By using a Li-820 infra-red CO_2 gas analyzer, an in situ measurement of Schima super-ba stem CO_2 efflux was conducted for three consecutive days from 17 to 19 October 2008. In the meantime, the stem temperature, xylem sap efflux density, and xylem CO_2 concentration were measured. The stem CO_2 efflux had a diurnal variation of "S" pattern, and differed significantly with stem diameter. There was a significant exponential relationship between stem CO_2 efflux and stem temperature (0. 24 < R~2 < 0. 78). The temperature coefficient (b) and regression coeffi-cient (R~2) were higher at nighttime than at daytime, and the Q_(10) value ranged from 2. 01 to 2. 79. The stem CO_2 efflux correlated significantly with the xylem CO_2 concentration, and the best regression curve was cubic (R~2= 0. 48). Excluding the effects of stem temperature, the stem CO_2 efflux showed a significant negative correlation with xylem sap flux density (r =-0.462). Therefore, only using simple temperature function to estimate stem CO_2 efflux would yield a significant error, and xylem sap flux should be taken into consideration in the stem CO_2 emux estimation. 相似文献
42.
分子系统发育对中国芸香科分类的贡献 总被引:2,自引:0,他引:2
The treatment of Rutaceae in the Chinese flora chose to follow Engler in recognizing Rutoideae and Toddalioideae as two separate subfamilies. Morphological and chemical comparisons, however, suggested grouping those two subfamilies in one subfamily, Rutoideae. This move has received support from molecular phylogenetic analyses, which also showed that the Chinese taxa in Euodia should be placed in Tetradium and Melicope following Hartley. Investigations into the chemistry and molecular phylogeny of Murraya also indicated that the species in the section Bergera without yuehchukene should be removed from Murraya. These findings clearly show the value of molecular cladistics to the taxonomy of Rutaceae in China and also directions for further investigations. Key words Bergera, Euodia, Melicope, Murraya, Rutaceae, Rutoideae, Tetradium, Toddalioideae. 相似文献
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比较了不同季节和冬眠时相中达乌尔黄鼠 (Citelleusdauricus)下丘脑内去甲肾上腺素 (noradrenaline ,NA)代谢和视前区 (POA)脑片中各类温敏神经元的比例、温度敏感性、放电活动的临界温度及下限温度 .结果表明 :与夏季动物相比 ,( 1)冬眠各时相中POA温敏神经元的比例和温敏性产生了与冬眠体温调节特性相关的适应性改变 ;( 2 )冬季和冬眠中POA神经元放电的下限温度和温敏神经元活动的临界温度均显著下移 ;( 3 )冬眠中POA神经元对NA反应的敏感性增高 ,冷敏神经元对NA的反应从夏季的抑制型转变为冬眠时的兴奋型 ;( 4)入眠和深冬眠时下丘脑内NA的含量和代谢水平下降 ,出眠时代谢水平升高 .这些变化可能解释动物入眠时主动降低体温和出眠时从深低体温中快速地升温的温度调节机理 . 相似文献
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Fucose is a major constituent of the protein- and lipid-linked glycans of
the various life-cycle stages of schistosomes. These fucosylated glycans
are highly antigenic and seem to play a role in the pathology of
schistosomiasis. In this article we describe the identification and
characterization of two fucosyltransferases (FucTs) in cercariae of the
avian schistosome Trichobilharzia ocellata, a GDP-Fuc:[Galbeta1--
>4]GlcNAcbeta-R alpha1-->3-FucT and a novel GDP-Fuc:Fucalpha-R
alpha1-- >2-FucT. Triton X-100 extracts of cercariae were assayed for
FucT activity using a variety of acceptor substrates. Type 1 chain
(Galbeta1- ->3GlcNAc) based compounds were poor acceptors, whereas those
based on a type 2 chain (Galbeta1-->4GlcNAc), whether
alpha2'-fucosylated, alpha3'-sialylated, or unsubstituted, and whether
present as oligosaccharide or contained in a glycopeptide or glycoprotein,
all served as acceptor substrates. In this respect the schistosomal alpha3-
FucT resembles human FucT V and VI rather than other known FucTs. N-
ethylmaleimide, an inhibitor of several human FucTs, had no effect on the
activity of the schistosomal alpha3-FucT, whereas GDP-beta-S was strongly
inhibitory. Large scale incubations were carried out with
Galbeta1-->4GlcNAc, GalNAcbeta1-->4GlcNAcbeta-O -(CH2)8COOCH3 and
Fucalpha1-->3GlcNAcbeta1-->2Man as acceptor substrates and the
products of the incubations were isolated using a sequence of
chromatographic techniques. By methylation analysis and 2D-TOCSY and
ROESY1H-NMR spectroscopy the products formed were shown to be Galbeta1--
>4[Fucalpha1-->2Fucalpha1-->3]GlcNAc,
GalNAcbeta1-->4[Fucalpha1-- >2Fucalpha1-->3]GlcNAcbe
ta-O-(CH2)8COOCH3, and Fucalpha1-->2Fucalpha1--
>3GlcNAcbeta1-->2Man, respectively. It is concluded that the alpha2-
FucT and alpha3-FucT are involved in the biosynthesis of the (oligomeric)
Lewisx sequences and the Fucalpha1-->2Fucalpha1-->3GlcNAc structural
element that have been described on schistosomal glycoconjugates.
相似文献
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Sexual conflict facilitates the evolution of traits that increase the reproductive success of males at the expense of components of female fitness. Theory suggests that indirect benefits are unlikely to offset the direct costs to females from antagonistic male adaptations, but empirical studies examining the net fitness pay‐offs of the interaction between the sexes are scarce. Here, we investigate whether matings with males that invest intrinsically more into accessory gland tissue undermine female lifetime reproductive success (LRS) in the cricket Teleogryllus oceanicus. We found that females incur a longevity cost of mating that is proportional to the partner’s absolute investment into the production of accessory gland products. However, male accessory gland weight positively influences embryo survival, and harmful ejaculate‐induced effects are cancelled out when these are put in the context of female LRS. The direct costs of mating with males that sire offspring with higher viability are thus compensated by direct and possibly indirect genetic benefits in this species. 相似文献