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11.
12.
Physiological influences on carbon isotope discrimination in huon pine (Lagarostrobos franklinii) 总被引:1,自引:0,他引:1
Summary Measurements of the light environment and stomatal and photosynthetic behaviour are reported for Huon Pine (Lagarostrobos franklinii, family Podocarpaceae) in western Tasmanian rainforest. For a variety of microenvironments, these are used in an analysis of stable carbon isotope measurements in the air, and in branch and leaf material, using a model for carbon isotope fractionation in leaves (Farquhar et al. 1982).The major features of 13C variations with respect to branch position can be explained in terms of the direct influence of light level acting via the rate of CO2 assimilation. In addition a relatively constant 13C gradient of about 2.6 between leaf tip and branch wood is observed.Alternative explanations are advanced for the tip-towood gradient in 13C. If the 13C of leaf tips is taken to represent the value for photosynthate, maintenance respiration is proposed as a mechanism for the further fractionation; a significant 13C depletion in respired CO2 is implied which is not supported by indirect measurements of atmospheric isotope ratio. Furthermore, an assumption of significant sampling errors (e.g. related to humidity effects on assimilation) is required to obtain good quantitative prediction of the light influence.If the branch wood 13C is taken to represent that of the photosynthate, the tip-to-wood gradient may find an explanation, via the model, in terms of tip tissue comprising carbon from immature cells. Translocation of photosynthate from exposed to shaded branches is then proposed as a means of obtaining quantitative agreement with the predicted light influence.The support provided for the applicability of the Farqunar et al. (1982) model in the field is discussed in the context of the problem of obtaining past global atmospheric CO2 levels from 13C in tree-rings. 相似文献
13.
DNA-binding proteins present in varicella-zoster virus-infected cells were identified by DNA-cellulose chromatography of radioactively labeled cell extracts. Seven virus-specific proteins, ranging in molecular weight from approximately 175,000 to 21,000, showed affinity for single- or double-stranded DNA or both. These proteins include the varicella-zoster virus major capsid protein, a phosphorylated tegument protein, and a 125,000-molecular-weight species which may be analogous to the major DNA-binding protein of herpes simplex virus. We also identified a number of DNA-binding phosphoproteins by these procedures. Finally, protein blot studies were carried out to determine whether these proteins bind preferentially to virus rather than to host cell DNA. 相似文献
14.
15.
Covariances of relatives stemming from a population undergoing mixed self and random mating 总被引:9,自引:0,他引:9
We consider covariances of all parent and first-generation relatives from outcrossing or self-fertilization in a parent population that is in equilibrium with respect to these processes. The results, which are for any number of alleles and loci with additive and dominance effects, are phrased in terms of six quadratic genetic components whose coefficients are given by descent measures for equilibrium populations. Because of the variation in the inbreeding coefficients for this system of mating, the expressions include joint contributions of loci to the variances and covariances of relatives. By inclusion of the full complement of relatives, all quadratic components can be estimated. The findings of Ghai (1982, Biometrics 38, 87-92) for compound functions of the covariances with two alleles at a single locus are analyzed in terms of the more general model. 相似文献
16.
A distance measure for populations diverging by drift only is based on the coancestry coefficient θ, and three estimators of the distance D = -ln(1 - θ) are constructed for multiallelic, multilocus data. Simulations of a monoecious population mating at random showed that a weighted ratio of single-locus estimators performed better than an unweighted average or a least squares estimator. Jackknifing over loci provided satisfactory variance estimates of distance values. In the drift situation, in which mutation is excluded, the weighted estimator of D appears to be a better measure of distance than others that have appeared in the literature. 相似文献
17.
E K Weir J A Will L J Lundquist J W Eaton E Chesler 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1983,173(1):96-103
Diamide oxidizes glutathione and other cellular sulfhydryl groups. It decreases calcium ATPase activity and alters mitochondrial calcium flux, probably as a result of the sulfhydryl oxidation. We examined the effect of diamide (5 mg/kg, iv) on pulmonary vascular reactivity in 12 anesthetized dogs. Diamide reversed the pulmonary vasoconstriction caused by hypoxia in seven dogs (control delta PVR + 2.5 +/- 0.6 mm Hg/liter/min; postdiamide delta PVR - 0.1 +/- 0.4 mm Hg/liter/min; P less than 0.01). The pulmonary pressor response to prostaglandin F2 alpha (5 micrograms/kg/min, iv) was also reduced (control delta PVR + 3.8 +/- 0.5 mm Hg/liter/min; postdiamide delta PVR + 1.1 +/- 0.7 mm Hg/liter/min; P less than 0.01). However, in a further five dogs, diamide had only a small effect on the pulmonary vasoconstriction caused by angiotensin II, while the pressor response to hypoxia was again inhibited. The mechanism by which diamide reverses pulmonary vasoconstriction is not certain but the effect is rapid, consistent, and reversible. Because the intravenous infusion of diamide does not produce systemic hypotension, during its period of action on the pulmonary vasculature, unlike the drugs currently available for the clinical treatment of pulmonary hypertension, further studies of its mechanism of action are indicated. 相似文献
18.
Several variations of a method for detecting linkage between a marker locus and a quantitative trait in full sib families are presented along with computational details. All variations are based on contrasts within qualifying families of three or more sibs. The empirical powers of the various test statistics, evaluated by simulation, were very similar, and also similar to that of Smith. These single-generation tests are likely to be successful only for many families and relatively tight linkage. 相似文献
19.
A study of the chromosomes of Cavia aperea and Galea musteloides has been made following the introduction into captivity of these two cavies from Argentina. The evolutionary relationships of the two genera have been considered, and the possible ancestry of C. porcellus from C. aperea was investigated in hybrids of the two species. 相似文献
20.
Behavior of pairs of loci in finite monoecious populations 总被引:4,自引:0,他引:4
Transition equations are established for descent measures for pairs of loci in finite randomly mating monoecious populations. The two special cases of equal chance gamete formation and two gametes per parent are considered in detail. The descent measures allow genotypic frequencies to be found but are used mainly to evaluate three quadrigenic moments, including the variance of the linkage disequilibrium. Numerical properties of these moments are compared to previously reported values. 相似文献