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1.
Tecomán, in the Mexican state of Colima, had the world's greatest production of lime Citrus aurantifolia Swingle. Typical farming systems in the area include: (a) high-input monoculture, (b) a high-input system in which lime trees
grow together with coconut palms, (c) a low-input system called "Family Farms" or "Family Gardens". In the Family Gardens,
cultural practices are minimal and other fruit trees (about 16 species) coexist with the lime trees. This traditional minimal
input system makes use of locally available resources and they are structurally very diverse. Arbuscular mycorrhizae may be
crucial for sustainable production in Family Gardens. Root colonization and spore populations of fungi were scored at 2-week
intervals in the three agroecosystems during a 6-month period. First samples were taken after the application of chemical
fertilizer and irrigation in the high-input systems. Root colonization of lime was much higher and consistent in the low-input
plots than in conventionally farmed plots, with colonization levels of 50–62% that remained the same throughout the sampling
time; the high-input systems showed a high variation and lower level of colonization, 36% and 27% in associated and monoculture
systems, respectively. Spore abundance was higher in the high-input systems but showed constant variation. The results suggest
a strong effect of agroecosystem on mycorrhizal colonization of lime roots.
Accepted: 12 September 1995 相似文献
2.
Effects of management practices on annual net N-mineralization in a restored prairie and maize agroecosystems 总被引:3,自引:0,他引:3
Nitrogen (N) mineralization is a spatially variable and difficult component of the N cycle to quantify accurately under field conditions. Net N-mineralization was compared by direct measurement, indirect estimate, and laboratory incubation for a restored tallgrass prairie and for deficiently and optimally N-fertilized, no-tillage (NT) and chisel-plowed (CP) maize (Zea mays L.) agroecosystems on Plano silt loam soil (fine-silty, mixed, superactive, mesic Typic Argiudoll) in Wisconsin, USA. Four years of in-situ field measurements using an incubated-soil-core/ion-exchange-resin-bag technique showed that land use significantly affected net N-mineralization. Net N-mineralization was consistently smaller in the restored prairie than in the maize agroecosystems and typically larger in the CP than in the NT maize agroecosystems. Three independent methods for indirectly estimating annual net N-mineralization (i.e., N budget residual, deficiently N-fertilized plant N uptake, and profile-scaled in-situ field measurements) were relatively consistent at capturing land-use and tillage effects on net N-mineralization. Laboratory incubation and periodic leaching of Fall-sampled soils demonstrated that both mineralized N and labile C were co-limiting factors influencing N-mineralization in agricultural soils and generally supported field measurements by showing a significant difference in net N-mineralization with and without added fertilizer-N. 相似文献
3.
Dicot wood is mainly composed of cellulose, lignin and glucuronoxylan (GX). Although the biosynthetic genes for cellulose and lignin have been studied intensively, little is known about the genes involved in the biosynthesis of GX during wood formation. Here, we report the molecular characterization of two genes, PoGT8D and PoGT43B, which encode putative glycosyltransferases, in the hybrid poplar Populus alba x tremula. The predicted amino acid sequences of PoGT8D and PoGT43B exhibit 89 and 75% similarity to the Arabidopsis thaliana IRREGULAR XYLEM8 (IRX8) and IRX9, respectively, both of which have been shown to be required for GX biosynthesis. The PoGT8D and PoGT43B genes were found to be expressed in cells undergoing secondary wall thickening, including the primary xylem, secondary xylem and phloem fibers in stems, and the secondary xylem in roots. Both PoGT8D and PoGT43B are predicted to be type II membrane proteins and shown to be targeted to Golgi. Overexpression of PoGT43B in the irx9 mutant was able to rescue the defects in plant size and secondary wall thickness and partially restore the xylose content. Taken together, our results demonstrate that PoGT8D and PoGT43B are Golgi-localized, secondary wall-associated proteins, and PoGT43B is a functional ortholog of IRX9 involved in GX biosynthesis during wood formation. 相似文献
4.
Was total primary production in the western Wadden Sea stimulated by nitrogen loading? 总被引:1,自引:1,他引:0
Borum and Sand-Jensen (1996) described empirical relationships between nitrogen (N) loadings from land and total (benthic
+ pelagic) primary production rates in shallow coastal marine waters. We applied these relationships to N loadings of the
western Wadden Sea system, and compared the production estimates with actually observed primary production rates of autotrophic
components (phytoplankton, microphytobenthos, macroalgae and seagrasses) for those years for which field data were available.
During the 1980s and early 1990s, primary production values appear in good agreement with those derived from the empirical
relationships. During the 1960s and early 1970s, however, these relationships substantially overestimated the total primary
production in the western Wadden Sea. Based on ambient nutrient concentrations and the Redfield ratio, production in that
period was considered not to be limited by N but by phosphorus (P) during most of the time. It is concluded that primary production
is not invariably stimulated by N loading from land. If other factors (i.e. additional nutrient sources, N:P ratios, internal
nutrient dynamics and co-limiting effects of nutrients and light) are not taken into account, management regulations that
are targeted at diminishing the effects of eutrophication hold the risk of seriously under- or overestimating nutrient reductions
that are thought necessary to achieve their goals.
Received: 30 November 1998 / Received in revised form: 12 July 1999 / Accepted: 15 July 1999 相似文献
5.
M. Joginadha Swamy M. Venkata Krishna Sastry Avadhesha Surolia 《Journal of biosciences》1985,9(3-4):203-212
Secondary structure prediction for the 4 legume lectins: Concanavalin A, soybean agglutinin, favabean lectin and lentil lectin,
was done by the method of Chou and Fasman. This prediction shows that these four lectins fall into a structurally distinct
class of proteins, containing high amounts of β-sheet and β-turns. There is a notable similarity in the gross structure of
these proteins; all four of them contain about 40–50% of β-sheet, 35–45 % β-turn and 0–10% of α-helix. When the secondary
structure of corresponding residues in each pair of these lectins was compared, there was a striking similarity in the Concanavalin
A-soybean agglutinin and favabean lectin-lentil lectin pairs, and considerably less similarity in the other pairs, suggesting
that these legume lectins have probably evolved in a divergent manner from a common ancestor. A comparison of the predicted
potential β-turn sites also supports the hypothesis of divergent evolution in this class of lectins. 相似文献
6.
F. A. Aravanopoulos 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,100(8):1203-1208
The relations between heterozygosity derived from a total of 12 variable isoenzyme loci and total above-ground leafless biomass
production were examined in four full-sib families of Salix exigua, a willow species important in breeding efforts for short-rotation intensive-culture plantations. Relations were investigated
by comparing the performance of heterozygotes with that of corresponding homozygotes in locus by locus comparisons, by investigating
multiple regression models with individual loci as independent variables, and by employing the adaptive distance model. All
these analytical approaches resulted in the manifestation of the absence of any relations between isoenzyme loci and biomass
production. Possible reasons that may account for these results are discussed.
Received: 8 October 1999 / Accepted: 4 November 1999 相似文献
7.
Atmospheric CO2 concentration has increased by 25% over the preindustrial level. A parallel increase in C concentration and decreases in N
concentration and δ13C of plants grown throughout this century have been observed in plant specimens stored in herbaria. We tested our previous
results in a study of 12 more species collected in the western Mediterranean throughout this century (1920–1930, 1945–1955,
and 1985–1990) and tree rings of Quercus pubescens from the same area. These changes were accompanied by apparent increases in condensed tannin concentration. A decreasing trend
in δ15N both in herbarium material and tree rings was also found, indicating that ecosystems might cope with higher plant N demand
by decreasing N losses and increasing N fixation and mineralization. These results may contribute to a better understanding
of the effects of global change on carbon and nitrogen cycling.
Received: 12 November 1995 / Accepted: 17 May 1996 相似文献
8.
The influence of different N sources on medium pH variation and the effect of the external mycelium of arbuscular mycorrhizal
fungi on nutrient dynamics were studied using a two-compartment, aseptic Petri plate system. VA mycorrhizal, transformed roots
of carrot (Daucus
carota L.) were cultured in the proximal compartment and external mycorrhizal mycelium in the distal compartment. The medium in
the distal compartament contained N either as NO3
– or as NH4
+. The pH and the anion and cation concentrations were measured every 15 days in filtrates prepared from the distal compartments.
Thirteen weeks after colonization, there was a significant basification or a light acidification of the NO3
– and NH4
+ medium, respectively. There was no change in NO3
– concentration but a significant decrease in NH4
+ concentration. Treatments containing N as NO3
– showed no variation in cations such asCa2+ and Mg2+ or anions such as PO4
2–, and SO4
2– but showed significant increases in the concentration of K+. Treatments containing N as NH4
+ showed no variation in cations or anions, except for increases in the concentrations of K+ and Cl–.
Accepted: 7 March 1996 相似文献
9.
Influence of two legume species on hyphal production and activity of two arbuscular mycorrhizal fungi 总被引:5,自引:0,他引:5
Two arbuscular mycorrhizal (AM) fungi (Glomus
mosseae and G. intraradices) were compared for abundance of intraradical and soil-borne hyphae in association with Astragalus sinicum, a small-seeded, and Glycine
max, a large-seeded legume. A. sinicum was more responsive than G. max to mycorrhizal formation, especially at early growth stages. Biomass allocation was greater in roots than shoots for mycorrhizal
A. sinicum, while the opposite was true for G. max. Hyphal development in root and soil compartments was estimated by trypan blue staining and after staining for succinate
dehydrogenase (SDH) or alkaline phosphatase (ALP) activity. Total fungal abundance increased steadily in roots and soil with
time to a maximum 8 weeks after planting. SDH- and ALP-active AM hyphae increased in roots during plant growth but decreased
in soil at later harvests. Mycorrhizal root mass in A. sinicum and G. max increased about 14-fold and 2.5-fold, respectively, but total length of soil hyphae produced per plant differed little, so
that the pattern of AM soil to root abundance of the two fungi varied considerably with the host plant.
Accepted: 23 July 1997 相似文献
10.
R. E. Voorrips M. C. Jongerius H. J. Kanne 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):75-82
A genetic map covering 615 cM in 12 linkage groups was assembled based on 92 RFLP and AFLP markers segregating in a population
of 107 doubled haploid lines (DH lines) of Brassica oleracea. The DH-line population was obtained through microspore culture from the of two homozygous parents: DH-line Bi derived from the cabbage landrace Bindsachsener, and DH-line Gr from broccoli cv ‘Greenia’.
Sixty-five percent of the loci, and in some cases complete linkage groups, displayed distorted segregation ratios, a frequency
much higher than that observed in populations of the same species. DH-line Bi was resistant to clubroot, which is caused by a Dutch field isolate of Plasmodiophora brassicae. Resistance in the DH-line population was determined in two ways: by assigning symptom grades to each plant, and by measuring
the fresh weights of the healthy and affected parts of the root system of each plant. Using a multiple QTL mapping approach
to analyze the fresh weight data, we found two loci for clubroot resistance; these were designated pb-3 and pb-4. The additive effects of these loci were responsible for 68% of the difference between the parents and for 60% of the genetic
variance among DH-line means. Also, indications for the presence of two additional, minor QTLs were found. Analysis of symptom
grades revealed the two QTLs pb-3 and pb-4, as well as one of the two minor QTLs indicated by analysis of the fresh weight data.
Received: 29 April 1996 / Accepted: 10 May 1996 相似文献
11.
Flow cytometric analysis of the chromosomes and stability of a wheat cell-culture line 总被引:3,自引:0,他引:3
T. Schwarzacher M. L. Wang A. R. Leitch G. Moore J. S. Heslop-Harrison N. Miller 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):91-97
A rapidly growing, long-term suspension culture derived from Triticum aestivum L. (wheat) was synchronized using hydroxyurea and colchicine, and a chromosome suspension with chromosomes was made. After staining with the DNA-specific fluorochromes Hoechst 33258 and Chromomycin univariate and bivariate flow-cytometry histograms showed 15 clearly resolved peaks corresponding to individual chromosome
types or groups of chromosomes with similar DNA contents. The flow karyotype was closely similar to a histogram of DNA content
measurements of Feulgen-stained chromosomes made by microdensitometry. We were able to show the stability of the flow karyotype
of the cell line over a year, while a parallel subculture had a slightly different, stable, karyotype following different
growth conditions. The data indicate that flow cytometric analysis of plant karyotypes enables accurate, statistically precise
chromosome classification and karyotyping of cereals. There was little overlap between individual flow-histogram peaks, so
the method is useful for flow sorting and the construction of chromosome specific-recombinant DNA libraries. Using bivariate
analysis, the AT:GC ratio of all the chromosomes was remarkably similar, in striking contrast to mammalian flow karyotypes.
We speculate about a fundamental difference in organization and homogenization of DNA sequences between chromosomes within
mammalian and plant genomes.
Received: 24 April 1996 / Accepted: 24 May 1996 相似文献
12.
Quantifying pathways of energy transfer between plants, pests, and beneficial insects is a necessary step toward maintaining
pest stable agroecosystems in the absence of chemical subsidies. A diet switching experiment utilizing a predatory ladybird
beetle, Hippodamia variegata (Goeze), evaluated the use of naturally occurring stable C and N isotopes as an economically feasible and safe method for
quantifying pathways of energy flow within agroecosystems. Stable isotope values of the ladybird beetle Coleomegilla maculata lengi (Timberlake) collected from an agroecosystem were used to estimate the relative amount of C and N derived from agricultural
plants and incorporated by ladybird beetles based on mass balance equations. At the beginning of the diet-switching experiment
δ13C and δ15N values of H. variegata (–12.0‰ and 6.3‰, respectively) differed by –0.2‰ and 2.9‰ from the aphids that were provided exclusively as their diet. These
data are consistent with previous estimates of trophic level isotope effects. After switching the diet of H.
variegata to an alternative food, isotope values of H. variegata gradually shifted toward expected values for individuals fed this diet (–22.9‰ and 8.8‰ for δ13C and δ15N values, respectively). Isotope values of another ladybird beetle, C. maculata, collected from the field indicated that in May, alfalfa and maize (pollen) obtained in the previous year contributed 32%
and 68% of the C or N to the diets of these individuals and in August, 52%, 6%, and 42% of the C or N assimilated by these
insects was derived from alfalfa, wheat, and maize, respectively. These data are consistent with expectations based on the
relative abundance of C. maculata in various crops during the season. The field and laboratory data are a clear indication that isotope values are sensitive
to dietary changes on a relatively short time scale (days) and provide a strong basis for the use stable C and N isotope to
trace energy flow patterns of these beneficial organisms within agroecosystems.
Received: 17 November 1995 / Accepted: 20 June 1996 相似文献
13.
M. Delorme D. W. Thomas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(7):427-434
Nitrogen (N) and energy (E) requirements were measured in adult Carollia perspicillata which were fed on four experimental diets. Bats ate 1.3–1.8 times their body mass ⋅ day-1 and ingested 1339.5–1941.4 kJ ⋅ kg-0.75 ⋅ day-1. Despite a rapid transit time, dry matter digestibility and metabolizable E coefficient were high (83.3% and 82.4%, respectively),
but true N digestibility was low (67.0%). Mass change was not correlated with E intake, indicating that bats adjusted their
metabolic rate to maintain constant mass. Bats were able to maintain constant mass with digestible E intake as low as 1168.7 kJ ⋅ kg-0.75 ⋅ day-1 or 58.6 kJ ⋅ . Metabolic fecal N and endogenous urinary N losses were 0.87 mg N ⋅ g-1 dry matter intake and 172.5 mg N ⋅ kg-0.75 ⋅ day-1, respectively, and bats required 442 mg N ⋅ kg-0.75 ⋅ day-1 (total nitrogen) or 292.8 mg N ⋅ kg-0.75 ⋅ day-1 (truly digestible nitrogen) for N balance. Based on E and N requirements and digestibilities, it was calculated that non-reproductive
fruit bats were able to meet their N requirements without resorting to folivory and without over-ingesting energy. It was
demonstrated that low metabolic fecal requirements allowed bats to survive on low-N diets.
Accepted: 23 June 1996 相似文献
14.
Using constant heat sap flow sensors, xylem water fluxes in ten tree species and two liana species were monitored for 5–10
days during the beginning of the wet season in May, 1993. For a subset of the trees, a branch was also monitored at the top
of the crown for 5 days. Xylem flux (J
S) was related diurnally in all plants to vapor pressure deficit (D) measured within the upper-third of the canopy, and to incoming shortwave radiation R
S above the canopy. Cross-correlation analysis was used to estimate time lags between diurnal patterns of J
S and D or R
S, and between J
S in stems and branches. The maximum correlation coefficient from cross-correlation of J
S with R
S (range=0.57–0.92) was often higher than the maximum of J
S with D (range=0.43–0.89), indicating that diurnal J
S was more dependent on R
S than D. Time lags (lag corresponding to maximum correlation) of J
S at stem-base with D was shorter (0–45 min) than with radiation (5–115 min), highly variable within a species, and uncorrelated to the height
or exposure of tree crowns or liana in the canopy. On a stand level, not accounting for the diel lag between stem sap flux
and canopy flux resulted in errors in estimated canopy transpiration of up to 30%.
Received: 19 October 1998 / Accepted: 8 June 1999 相似文献
15.
During the normal development of echinoids, an animal cap consisting of 8 mesomeres in a 16-cell stage embryo differentiates
exclusively into ectoderm. Micromeres in an embryo at the same stage differentiate into primary mesenchyme cells (PMC) and
coelomic pouch constituents. An animal cap and a quartet of micromeres were isolated from a 16-cell stage embryo and recombined
to make a chimeric embryo devoid of presumptive endoderm and secondary mesenchyme cells (SMC). The PMC in the chimeric embryo
were completely removed at the mesenchyme blastula stage. The PMC-depleted chimeric embryos formed an archenteron derived
from the mesomeres. Some secondary mesenchyme-like cells (induced SMC) were released from the archenteron tip. A considerable
fraction of the induced SMC formed the typical mesenchyme pattern after migrating into the vegetal region, synthesized skeletogenic
mesenchyme cell-surface protein (msp130) and produced the larval skeleton. These findings indicate that induced SMC derived
from the presumptive ectoderm have the same nature as natural SMC in both the timing of their release and their skeletogenic
potential expressed in the absence of PMC.
Received: 14 November 1996 / Accepted: 30 December 1996 相似文献
16.
M. M. R do Rêgo C. H. Bruckner E. A. M. da Silva F. L. Finger D. L. de Siqueira A. A. Fernandes 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(3-4):564-568
The self-incompatibility in yellow passion fruit was previously described as homomorphic sporophytic with monofactorial inheritance.
Five progenies were obtained by bud-selfing. The plants of these progenies were selfed, reciprocally crossed within each progeny
and crossed with known incompatible phenotypes to identify their phenotypic group. Fruit set was evaluated at the 7th day
after pollination. Two progenies consisted of two self-incompatible groups, the other three formed three suck groups. The
groups were identified as S1, S2, S3, S4, S5 and S6. The results provide evidence that the self-incompatibility of passion fruit is controlled by two loci, the S-gene and another,
whose expression needs to be investigated.
Received: 20 June 1998 / Accepted: 13 July 1998 相似文献
17.
The present study investigated the growth, secondary production and gonad development of two co-existing amphioxus species Branchiostoma belcheri and B. malayanum in subtropical Hong Kong from June 2005 to June 2006. Based on the modal progression analysis, amphioxus populations were decomposed into separate cohorts. The von Bertalanffy growth models were also estimated according to the size incremental data. From the growth models, the size ranges of one, two and three-year-old B. belcheri were estimated to be 5-28 mm, 28-38 mm and 38-45 mm BL, respectively; while the one and two-year-old B. malayanum were estimated to be 7-30 mm and 30-35 mm BL, respectively. The secondary production was calculated at 1.15 g m− 2 yr− 1 DW or 0.63 g m− 2 yr− 1 AFDW for B. belcheri with density 424 ind m− 2, and 0.51 g m− 2 yr− 1 DW or 0.40 g m− 2 yr− 1 AFDW for B. malayanum with density 121 ind m− 2. The production to biomass ratio (P/B) was 1.13 for B. belcheri and 0.98 for B. malayanum. Changes in the gonad length index indicated that B. belcheri spawned mainly in June and July, while B. malayanum mainly in April and August. As compared with B. belcheri, B. malayanum was characterized by rapid growth, shorter life span, early maturity and lower population density. Such differences in population dynamics may allow both species to share a similar habitat and co-exist in subtropical waters of Hong Kong. 相似文献
18.
Polymorphism, distribution, and segregation of AFLP markers in a doubled haploid rice population 总被引:18,自引:0,他引:18
M. Maheswaran P. K. Subudhi S. Nandi J. C. Xu A. Parco D. C. Yang N. Huang 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):39-45
We exploited the newly developed amplified fragment length polymorphism (AFLP) technique to study the polymorphism, distribution
and inheritance of AFLP markers with a doubled haploid rice population derived from ‘IR64’/‘Azucena’. Using only 20 pairs
of primer combinations, we detected 945 AFLP bands of which 208 were polymorphic. All 208 AFLP markers were mapped and distributed
over all 12 chromosomes. When these were compared with RFLP markers already mapped in the population, we found the AFLP markers
to be highly polymorphic in rice and to follow Mendelian segregation. As linkage map of rice can be generated rapidly with
AFLP markers they will be very useful for marker-assisted backcrossing.
Received: 11 April 1996 / Accepted: 14 June 1996 相似文献
19.
Highly polymorphic microsatellites of rice consist of AT repeats, and a classification of closely related cultivars with these microsatellite loci 总被引:20,自引:3,他引:20
H. Akagi Y. Yokozeki A. Inagaki T. Fujimura 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):61-67
Microsatellites consisting of AT repeats are highly polymorphic in rice genomes and can be used to distinguish between even
closely related japonica cultivars in Japan. Polymorphisms of 20 microsatellite loci were determined using 59 japonica cultivars,
including both domestic and modern Japanese cultivars. Although the polymorphisms of these 20 microsatellite loci indicated
that the Japanese cultivars were genetically quite similar, microsatellites consisting of AT repeats showed high gene diversity
even among such closely related cultivars. Combinations of these hypervariable microsatellites can be employed to classify
individual cultivars, since the microsatellites were stable within each cultivar. An identification system based on these
highly polymorphic microsatellites could be used to maintain the purity of rice seeds by eliminating contamination. A parentage
diagnosis using 17 polymorphic microsatellite loci clearly demonstrated that plants which carried desired chromosome regions
had been selected in breeding programs. Thus, these hypervariable microsatellites consisting of AT repeats should promote
the selection of plants which carry desired chromosomes from genetically similar parents. Backcrossing could also help to
eliminate unnecessary chromosome regions with microsatellite polymorphisms at an early stage in breeding programs.
Received: 8 July 1996 / Accepted: 12 July 1996 相似文献
20.
The source of nitrogen in the spores of arbuscular mycorrhizal (AM) fungi was quantified by a 15N-labeling technique. N was applied as coated urea to the soil and in solution to plant shoots. Soil-applied fertilizer had
a significant effect on spore % 15N (P<0.01), with a 24–75% contribution to spore N. Fertilizer applied to either alfalfa shoots or bahia grass shoots had little
effect on spore % 15N, accounting for 0–14% or 1–9% of spore N, respectively. These results indicate that AM fungi obtain spore N mostly from
the soil. The small amount of spore N originating from shoot-applied N may have been obtained via root exudation.
Accepted: 6 November 2000 相似文献