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1.
Differences in chemical composition of plants grown at constant relative growth rates with stable mineral nutrition 总被引:11,自引:0,他引:11
R. H. Waring A. J. S. McDonald S. Larsson T. Ericsson A. Wiren E. Arwidsson A. Ericsson T. Lohammar 《Oecologia》1985,66(2):157-160
Summary Leaf chemistry of a willow clone (Salix aquatica Smith) differed significantly when grown at constant relative growth rates depending upon the relative availability of nutrients and light. Concentration of amino acids and nitrate were high in plants grown with a relative surplus of nutrients. Concentrations of starch, tannin, and lignin, on the other hand, were high in plants grown with a relative surplus of carbon. Photosynthetic rates, expressed per unit leaf area, were similar when plants were grown under high light conditions, regardless of nutrient availability. Dark respiration was much higher in plants supplied with abundant nutrients than in those with a more limited supply, reflecting differences in nitrogen concentration of the tissue. The experimental approach allows plants to be grown to a standard size with differing, but highly uniform chemistry. Plants grown in such a manner may provide good experimental material to evaluate interactions between herbivores or pathogens and their hosts. 相似文献
2.
3.
7C female sterile mutants fail to accumulate early eggshell proteins necessary for later chorion morphogenesis in Drosophila 总被引:1,自引:0,他引:1
Seven noncomplementing female sterile mutations that affect eggshell assembly in Drosophila have been mapped to the 7C1-3 region of the X-chromosome. TEM of the mature eggshell of one of the alleles, fs(1)410, shows a lack of organization within the endochorion and an accumulation of electron dense material in the vitelline membrane of stage 14 eggchambers. SDS-PAGE of radiolabeled eggshell proteins shows that two proteins, s67 and s85, fail to accumulate in the fs(1)410 eggshell. In wild-type flies s85 is produced during stage 10 of oogenesis and then processed to s67 in stages 13 and 14. Neither s85 nor an additional stage 10 specific follicle cell protein (s130) are detected in fs(1)410 or four of the mutant alleles. Short-term labeling studies, analyses of in vitro translation products, and the simultaneous occurrence of s85 and s130 as electrophoretic variants in geographic fly strains indicate s85 is derived from s130. Although major biochemical differences appear in stage 10, mutant and wild-type eggshells are morphologically indistinguishable until stages 13-14. These results suggest that follicle cell proteins synthesized during the time of vitelline membrane deposition (stage 10) are important for proper assembly of the chorion layers during stages 13 and 14. 相似文献
4.
Summary We tested the Enemy Impact Hypothesis, which predicts that communities of one tropic level are organized by the tropic level above. In the case of gallforming insect communities, the hypothesis predicts that gall morphology will diverge, minimizing the number of parasitoids shared among species. We used the monophyletic group of gallforming cecidomyiids (Asphondylia spp.) on creosote bush (Larrea tridentata) to test this hypothesis, predicting that species with thicker gall walls should exclude species of parasitoids with shorter ovipositors and have lower levels of parasitism. Of 17 parasitoid species reared from Asphondylia galls on creosote bush, 9 accounted for over 98% of parasitism. Seven of these 9 species had ovipositors long enough to penetrate 10 of 13 gall morphs measured. There was no significant relationship between gall wall thickness and number of associated parasitoid species (r
2=0.01, P>0.05, n=13). There was no relationship between gall wall thickness and types of parasitoid species colonizing galls: parasitoids with the shortest ovipositors colonized all types of gall morphs and were dominant members of the parasitoid assemblages in galls with the thickest walls. Ultimately, there were no significant differences in percent parasitism among Asphondylia species, regardless of gall wall thickness. We found no difference in numbers of associated parasitoids or percent parasitism in galls with different textures (e.g. hairy versus smooth), different locations on the plant or different phenologies. Our results suggest that enemy impact has not influenced the diversity of this gall community. Gall wall thickness, phenology, location on the plant and surface structure do not appear to influence the distribution of parasitoid species. Other explanations are offered to account for diversity in gall morphology among these species. 相似文献
5.
The alpha-like globin gene cluster in rabbits contains embryonic zeta-
globin genes, an adult alpha-globin gene, and theta-globin genes of
undetermined function. The basic arrangement of genes, deduced from
analysis of cloned DNA fragments, is 5'-zeta 0-zeta 1-alpha 1-theta 1- zeta
2-zeta 3-theta 2-3'. However, the pattern of restriction fragments
containing zeta- and theta-globin genes varies among individual rabbits.
Analysis of BamHI fragments of genomic DNA from 24 New Zealand white
rabbits revealed eight different patterns of fragments containing
zeta-globin genes. The large BamHI fragments containing genes zeta 0 and
zeta 1 are polymorphic in length, whereas a 1.9-kb fragment containing the
zeta 2 gene and the 3.5-kb fragment containing the zeta 3 gene do not vary
in size. In contrast to this constancy in the size of the restriction
fragments, the copy number of the zeta 2 and zeta 3 genes does vary among
different rabbits. No length polymorphism was detected in the BamHI
fragments containing the theta-globin genes, but again the copy number
varies for restriction fragments containing the theta 2 gene. The alpha 1-
and theta 1-globin genes are located in a nonpolymorphic 7.2-kb BamHI
fragment. The combined data from hybridization with both zeta and theta
probes shows that the BamHI cleavage pattern does not vary within the
region 5'-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3', but the pattern
genomic blot-hybridization patterns for the progeny of parental rabbits
with different zeta-globin gene patterns shows that the polymorphic
patterns are inherited in a Mendelian fashion. Two different haplotypes
have been mapped based on the genomic blot-hybridization data. The
variation in the alpha-like globin gene cluster in the rabbit population
results both from differences in the copy number of the duplication block
containing the zeta-zeta-theta gene set and from the presence or absence of
polymorphic BamHI sites.
相似文献
6.
Gwendolyn L. Waring 《Ecological Research》1988,3(3):205-216
The effects of watering and fertilizer treatments on the vigor and biochemistry of the willow,Salix lasiolepis, and subsequent colonization and survivorship of its gallforming herbivore,Euura lasiolepsis, were investigated in two field experiments. Some plants received low (LW), intermediate (MW) or high (HW) levels of water
as treatments, while others received no (OF), low (LF) or high (HF) fertilizer levels. In the watering experiment, plant protein
concentrations decreased, while growth rate and number of galls per plant increased with increased water treatments. Plant
growth proved to be the best correlate of sawfly attack. Sawfly survivorship increased slightly with greater watering, and
phenol concentrations showed no pattern among treatments. In the fertilization experiment, leaf protein increased with fertilization,
although shoot length, number of galls and survivorship ofE. lasiolepis survivorship were greatest in intermediate treatment plants. In both experiments, plant growth, rather than protein or phenol
levels, was the best predictor of sawfly attack and survivorship.
In a natural experiment with galls on wild plants, galled tissue had significantly greater protein concentrations and lower
phenol concentrations than did ungalled tissue. We suggest that gallformers modify host plant biochemistry within willow galls,
which may explain why the chemical parameters of ambient plant quality we tested were less predictive than plant growth. 相似文献
7.
Four genes expressed during the period of vitelline membrane formation are clustered within 8 kb of DNA in region 26A of the second chromosome. Temporal and quantitative difference in the profiles of accumulated RNA suggest that the genes are independently regulated although they are selectively expressed during the stages of vitelline membrane biosynthesis. In situ hybridization and S1 analyses of RNAs from fractionated eggchambers established that these genes are active only in the follicle cells. S1 mapping with in vitro synthesized RNA probes shows that three of the genes are tandemly oriented. All four appear to be intronless. In vitro translation products from hybrid-selected RNAs indicate that two of these genes code for major vitelline membrane proteins. Sequence analysis of these two genes support this conclusion. The cell- and stage-specific expression of the other two genes, encoding less abundant RNAs, suggests that they also play a role in early eggshell production. 相似文献
8.
Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium 总被引:13,自引:9,他引:4 下载免费PDF全文
Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel. 相似文献
9.
DNA requirements at the bacteriophage G4 origin of complementary-strand DNA synthesis. 总被引:2,自引:0,他引:2 下载免费PDF全文
An in vivo assay was used to define the DNA requirements at the bacteriophage G4 origin of complementary-strand DNA synthesis (G4 origin). This assay made use of an origin-cloning vector, mRZ1000, a defective M13 recombinant phage deleted for its natural origin of complementary-strand DNA synthesis. The minimal DNA sequence of the G4 genome sufficient for the restoration of normal M13 growth parameters was determined to be 139 bases long, located between positions 3868 and 4007. This G4-M13 construct was also found to give rise to proper initiation of complementary-strand synthesis in vitro. The cloned DNA sequence contains all the regions of potential secondary structure which have been implicated in primase-dependent replication initiation as well as additional sequence information. To address the role of one region which potentially forms a DNA secondary structure, the DNA sequence internal to the G4 origin was altered by site-directed mutagenesis. A 3-base insertion at the AvaII site as well as a 17-base deletion between the AvaI and AvaII sites both resulted in loss of origin function. The 17-base deletion was also generated within the G4 genome and found to dramatically reduce the infectious growth rate of the resulting phage. These results are discussed with respect to the role of the G4 origin as the recognition site for primase-dependent replication initiation and its possible role in stage II replication. 相似文献
10.
A Cornish K R Fox S Santikarn M J Waring D H Williams 《Journal of general microbiology》1985,131(3):561-570
The quinoxaline chromophores of the antibiotics produced by Streptomyces triostinicus are derived from tryptophan. Protoplasts of this organism made novel products when they were incubated with DL-5-fluorotryptophan or DL-6-fluorotryptophan. When added to batch cultures of the organism, DL-5-fluorotryptophan, at concentrations as low as 10 microM, inhibited both mycelial growth and triostin production, but gave rise to novel products. These have been characterized, using fast atom bombardment mass spectrometry, as novel triostins in which one or both of the quinoxaline rings contain an atom of fluorine. The chromatographic properties of the triostins arising from the incorporation of DL-5-fluorotryptophan are very similar to those of triostins containing chlorine or bromine at position 6 of the quinoxaline ring; they are clearly different from those having a chlorine atom at position 7. Accordingly, it is suggested that the carbon atom at position 5 of the indole ring of tryptophan ends up at position 6 of the quinoxaline ring system in triostins A and C. 相似文献