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91.
Demographic genetics of the American beech (Fagus grandifolia Ehrh.) III. Genetic substructuring of coastal plain population in Maryland 总被引:2,自引:0,他引:2
KEIKO KITAMURA TATSUYOSHI MORITA† HIROSHI KUDO‡ JAY O'NEILL§ FREDERICH H. UTECH¶ DENNIS F. WHIGHAM§ SHOICHI KAWANO 《Plant Species Biology》2003,18(1):13-33
Spatiotemporal genetic substructurings were investigated in the American beech population of the east-central coastal plain in Maryland. All trees including seedlings, various sizes of juveniles, and mature trees within the study site (10 × 100 m) were mapped, diameters measured, and leaves collected for allozyme analyses. Eleven polymorphic loci in eight enzyme systems were examined: 6Pgdh2, 6Pgdh3, Acp2, Adh1, Adh2, Fum, Got1, Got3, Lap, Pgi, and Pgm2. A total of 1945 trees were analyzed and 595 multilocus genotypes were detected. Six size-classes and 10 spatial blocks were discriminated for spatiotemporal analyses. Parameters for genetic variations (heterozygosity, Simpson's index, Shannon-Weaver's index, and inbreeding coefficient) decreased in larger size-classes. These genetic parameters fluctuated in spatial blocks of 10 m intervals, in which certain alleles were characteristic of specific blocks. The spatial autocorrelation by Moran's I and coancestry revealed the ranges of genetic relatedness to be only 20–30 m. Multilocus genotype analyses showed that higher genetic variations occur in larger size-classes and at gap openings where seed shadows for mother trees are overlapped. The relationships among reproductive trees, seedlings and juveniles suggested that the seed dispersal range of the American beech is normally in the range of 30–40 m. The mechanisms of a remarkably high genetic polymorphism maintained in this once artificially disturbed and grazed forest are discussed as related to conservation biology. 相似文献
92.
BRENDAN CHOAT WILLIAM M. DRAYTON CRAIG BRODERSEN MARK A. MATTHEWS KEN A. SHACKEL HIROSHI WADA ANDREW J. MCELRONE 《Plant, cell & environment》2010,33(9):1502-1512
Among woody plants, grapevines are often described as highly vulnerable to water‐stress induced cavitation with emboli forming at slight tensions. However, we found native embolism never exceeded 30% despite low xylem water potentials (Ψx) for stems of field grown vines. The discrepancy between native embolism measurements and those of previous reports led us to assess vulnerability curve generation using four separate methods and alterations (i.e. segment length and with/without flushing to remove embolism prior to measurement) of each. Centrifuge, dehydration and air‐injection methods, which rely on measurement of percentage loss of hydraulic conductivity (PLC) in detached stems, were compared against non‐invasive monitoring of xylem cavitation with nuclear magnetic resonance (NMR) imaging. Short segment air‐injection and flushed centrifuge stems reached >90 PLC at Ψx of‐0.5 and ?1.5 MPa, respectively, whereas dehydration and long‐segment air‐injection measurements indicated no significant embolism at Ψx > ?2.0 MPa. Observations from NMR agreed with the dehydration and long segment air‐injection methods, showing the majority of vessels were still water‐filled at Ψx > ?1.5 MPa. Our findings show V. vinifera stems are far less vulnerable to water stress‐induced cavitation than previously reported, and dehydration and long segment air‐injection techniques are more appropriate for long‐vesseled species and organs. 相似文献
93.
ABSTRACT We found a new acoustic signal in Drosophila simulans (si) and D. melanogaster (me). It is a ‘rejection signal’ (RS) produced by adult males and young males and females in response to the courting behaviour of mature males who emit ‘pulse songs’ (i.e. love song: LS). It occurs most frequently in si, less in adults me except if the interacting males belong to different chemical morphs (i.e. temperate or equatorial population). There are no differences in the LS characteristics directed to various sexes and ages. The RSs produced by adult males or by young animals do not differ significantly either. They are emitted by neither virgin nor fecundated adult me females but a few times by virgin adult si females. The RS (like the LS) is a multipulse signal but intervals between pulses are about twice those of LS, around 90 ms for si and 80 ms for me. They are very irregular, as is the distribution of energy along the bandwidth mainly between 300 and 800 Hz for si and 200 and 600 Hz for me. The sound level of the RS is from 10 to 20 dB less than the LS. The RS seems to be linked to the ‘flicking’ behaviour produced by both wings, while the LS always corresponds to the so-called ‘wing vibration’. 相似文献
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95.
Change of statistical distribution of cell size occurring inthe synchronous culture of Chlorella ellipsoidea was followedby using a COULTER counter. The culture was started using apopulation of D-cells which showed a sharp distribution of cellsize. During the growth phase, there occurred characteristicchanges in the height and shape of the distribution curve; namely,the height first decreased with broadening of the distributionand then increased to the level even higher than the originalpeak. The broadening of the curves, which indicates the loweringof degree of homogeneity of population, occurred during theperiod of most active growth, and the homogeneity was restoredat later stages of ripening where the growth became sluggish.When the ripened cells (L3) were transferred to the darknesstheir volume decreased to some extent before the occurrenceof cellular division. It was assumed that the shrinkage of cellsobserved may be partly due to exudation of water from the cellsand partly to the consumption of fuel material caused by enhancedrespiration, both having been shown to occur at the stage ofcell maturation. (Received June 12, 1964; ) 相似文献
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97.
Abstract. Phylogenetic relationships among tribes in the tachinid subfamily Exoristinae (Diptera, Tachinidae) are inferred from four genes, namely white, 18S, 28S and 16S rDNA. For phylogenetic inferences, maximum parsimony, maximum likelihood and Bayesian Markov chain Monte Carlo analyses were performed. The resultant, very similar, trees are nearly concordant with the traditional classification based on morphological characters. Our results suggest that the Tachinidae are monophyletic and sister to the Sarcophagidae. The tribal relationships within Exoristinae are supported in part with high reliabilities and are similar to those inferred by Stireman. Based on the resultant trees, the phylogenetic relationships and possible morphological synapomorphies were investigated. In addition, we evaluated the transformation of female reproductive habits in the Exoristinae, finding support for the hypothesis that ovolarviparity evolved independently from oviparity in several clades, and obtaining different results concerning the evolutionary history of micro‐ovolarviparity depending on character optimization. 相似文献
98.
Mitochondria and chloroplasts are structurally associated inthe bundle sheath cells of Portulaca oleracea L., an NAD malicenzyme type C4 plant. These associations occur in some restrictedregions where the mitochondrial cristae extend inwards. Exposureof plants to 1.0 µ111 SO2 for 3 h induced shrinkageof mitochondria of the bundle sheath cells, which further visualizedthe structural association between the organelles. C4 plant, chloroplast, mitochondrion, Portulaca oleracea, sulphur dioxide 相似文献
99.
100.
SUSUMU IKEGAMI JUNJI IMAYOSHI NOBUO TAKAHASHI HIROSHI NAGANO 《Development, growth & differentiation》1985,27(3):393-403
Dihydrofolate reductase in immature oocytes of the starfish, Asterina pectinifera, is estimated to be 12 pg per oocyte. After completion of meiosis, the quantity of the enzyme is approximately 20 pg per egg. The content of the enzyme in the egg is kept nearly constant at this value from fertilization to the beginning of blastulation. Methotrexate, an analogue of dihydrofolate, at 20 μM did not affect meiotic maturational process and fertilization, but inhibited embryonic development at the 512-cell stage which corresponds to the beginning of blastulation. Incorporation of externally supplied deoxy[3H]uridine into DNA of the embryos cultured in the continuous presence of 20 μM of methotrexate stopped at the 256-cell stage, suggesting that the cessassion of development of the embryo at the 512-cell stage was caused by inhibition of DNA synthesis at the preceding stage. Uptake of [3H]methotrexate was low at early cleavage stages but increased just before blastulation. Externally supplied 1 mM of thymidine counteracted the inhibitory effect of methotrexate at 20 μM, suggesting that the starvation of the methotrexate-treated embryo for thymidine nucleotides halted DNA synthesis at the beginning of blastulation. 相似文献