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1.
Walter M. Fitch 《Journal of molecular evolution》1981,18(1):30-37
Summary A procedure is presented that forms an unrooted tree-like structure from a matrix of pairwise differences. The tree is not formed a portion at a time, as methods now in use generally do, but is formed en toto without intervening estimates of branch lengths. The method is based on a relaxed additivity (four-point metric) constraint. From the tree, a classification may be formed. 相似文献
2.
Determination of phytohormones in phloem exudate from tree species by radioimmunoassay 总被引:3,自引:0,他引:3
A sensitive and specific radioimmunoassay was used to determine quantitatively four of the most important phytohormones in the phloem exudate from 14 different tree species of 8 genera. For cytokinins and indole-3-acetic acid (IAA) we found higher concentrations than those reported previously for other species. The gibberellin values were of the same order of magnitude as in earlier analyses (with different methods) of tree phloem exudates, but lower than the ones reported for Ricinus. Free abscisic acid (ABA) was found in tree phloem exudates in similar concentrations as before in Yucca or palm phloem exudate, but at considerably lower ones than reported for Ricinus and in Lupinus phloem exudate.Abbreviations IAA
indole-3-acetic acid
- ABA
abscisic acid
- GA
gibberellic acid 相似文献
3.
Colin?M.?OriansEmail author Margret?M.?I.?van?Vuuren Nancy?L.?Harris Benjamin?A.?Babst George?S.?Ellmore 《Trees - Structure and Function》2004,18(5):501-509
The capture of patchily distributed nutrients by tree roots has received extensive research, but the fate of those nutrients has not. We performed experiments to determine if nutrient transport within tree species is preferentially transported from specific roots to specific branches. Saplings of five species with contrasting growth requirements were examined: two Betula species (B. papyrifera and B. lenta), Populus tremuloides, and two Acer species (A. saccharum and A. rubrum). To quantify patterns of long-distance transport, we examined the accumulation of safranin-O dye and 15N in branches when these tracers were applied to isolated lateral roots (dye and 15N) and to the main root system (15N). Because transport of nutrients between sectors requires flow through intervessel pit pairs of adjacent xylem vessel elements, we quantified the area of intervessel pits, the number of pits per unit vessel wall area, and the % vessel wall area as pits in Acer and Betula. We found that the two Betula species were integrated (tracers applied to isolated roots were likely to accumulate in all branches), while P. tremuloides and the two Acer species were sectorial (tracer accumulation was more concentrated in particular branches). Betula had the largest number of intervessel pits per unit vessel wall area and the largest percentage of vessel wall area as pits. The high density of bordered pits may explain the ease of tracer movement throughout the two Betula species. Greater integration may allow certain trees (e.g., Betula) to exploit nutritionally patchy environments such as rocky soils, and may alter plant-herbivore interactions. 相似文献
4.
Fluctuations in densities of woody plant species were monitored in plots within three northern Botswana woodland types subjected to elephant damage and burning. Woodlands dominated by Baikiaea plurijuga and Colophospermum mopane sustained significant changes occurring on an annual basis, whereas Acacia erioloba plots maintained a typical structure. The structure of A. erioloba woodlands appeared to be influenced by factors other than elephants and the occurrence of fire. Woodlands dominated by C. mopane plants were subjected to obtrusive elephant damage, although the densities of tall trees remained largely unchanged. The effects of fire were most prominent in B. plurijuga woodlands. Tree densities declined consistently and plants of lower height classes, such as shrubs and seedlings increased in densities in areas subjected to a high occurrence of fire. 相似文献
5.
《Journal of biological education》2012,46(3):186-187
The simple conductivity method described here uses a home-made electrode for determining the salinity of estuarine waters 相似文献
6.
Biodiversity conservation,yield, and alternative products in coffee agroecosystems in Sumatra,Indonesia 总被引:1,自引:0,他引:1
Stacy?M.?PhilpottEmail author Peter?Bichier Robert?A.?Rice Russell?Greenberg 《Biodiversity and Conservation》2008,17(8):1805-1820
Agroecology and conservation must overlap to protect biodiversity and farmer livelihoods. Coffee agroecosystems with complex
shade canopies protect biodiversity. Yet, few have examined biodiversity in coffee agroecosystems in Asia relative to the
Americas and many question whether coffee agroecosystems can play a similar role for conservation. We examined vegetation,
ant and bird diversity, coffee yields and revenues, and harvest of alternative products in coffee farms and forests in SW
Sumatra, Indonesia near Bukit Barisan Selatan National Park (BBS). BBS is among the last habitats for large mammals in Sumatra
and >15,000 families illegally cultivate coffee inside of BBS. As a basis for informing management recommendations, we compared
the conservation potential and economic outputs from farms inside and outside of BBS. Forests had higher canopy cover, canopy
depth, tree height, epiphyte loads, and more emergent trees than coffee farms. Coffee farms inside BBS had more epiphytes
and trees and fewer coffee plants than farms outside BBS. Tree, ant, and bird richness was significantly greater in forests
than in coffee farms, and richness did not differ in coffee farms inside and outside of BBS. Species similarity of forest
and coffee trees, ants, and birds was generally low (<50%). Surprisingly, farms inside the park were significantly older,
but farm size, coffee yields, and revenues from coffee did not depend on farm location. Farmers outside BBS received higher
prices for their coffee and also more often produced other crops in their coffee fields such that incentives could be created
to draw illegal farmers out of the park. We also discuss these results with reference to similar work in Chiapas, Mexico to
compare the relative contribution of coffee fields to conservation in the two continents, and discuss implications for working
with farmers in Sumatra towards conservation plans incorporating sustainable coffee production. 相似文献
7.
B. Ziegenhagen M. Fladung 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(8):1065-1071
This paper reports on a PCR-RFLP analysis in a chloroplast DNA region consisting of coding and intergenic spacer sequences
of trnS and the adjacent psbC gene. This region was PCR-amplified in 62 woody plant species, predominantly tree species, that represent a broad systematic
range in both gymnosperms and dicotyledonous angiosperms. The amplification products were digested by the restriction endonuclease
HaeIII (GG↓CC). Fourteen different restriction patterns occurred, 5 of which characterised representatives of the gymnosperms,
and 9 angiosperm representatives. A single restriction site polymorphism revealed most of the species to share restriction
patterns. Groups formed which showed relationships to plant systematic units. This phenomenon is discussed with regard to
the psbC gene and the GGCC motif for tracing species’ relationships on a high taxonomic level of gymnosperms and angiosperms.
Received: 5 June 1996/Accepted: 20 September 1996 相似文献
8.
Summary Glx and Asx ambiguities introduce errors into evolutionary conclusions drawn from the sequences of incompletely analyzed proteins. These errors are of sufficient magnitude to invalidate some of these conclusions. 相似文献
9.
Exploratory analysis of marked point patterns has previously been conducted using two disjoint techniques, namely the mark correlation function and spectral analysis. Our purpose here is to present two alternative autocovariance estimators to the mark correlation function which not only apply in both planar and lattice situations, but which in the lattice case can also be considered in terms of the inverse Fourier transform of the spectrum. Moreover, they can be applied to isotropic or anisotropic marked point patterns. Various examples are presented to show how these estimators perform when applied to data sets possessing different kinds of mark structure, and a rank test procedure is proposed to enable the construction of empirical tests of hypothesis. 相似文献
10.
Spatial heterogeneity of light penetration through periderm and lenticels and concomitant patchy acclimation of corticular photosynthesis 总被引:3,自引:0,他引:3
The hypothesis that lenticels may act as a gate for light penetration through the highly light absorptive periderm, was investigated. Yet, transmittance of isolated periderms from ten tree species was considerably higher in the non-lenticel than in the lenticel regions. Depending on species, the lower transmittance of lenticels was due to either higher reflectance and/or higher absorptance. Corticular tissue regions below lenticels were more shade acclimated. Chlorophyll fluorescence images showed lower PS II effective yields, a lower potential for non-photochemical quenching and a possibly higher risk of photoinhibition in the corticular areas under the lenticels in most of the cases. 相似文献