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61.
Accumulation and Loss of Nitrogen in White Clover (Trifolium repens L.) Plant Organs as Affected by Defoliation Regime on Two Sites in Norway 总被引:1,自引:0,他引:1
Ievina Sturite Marianne Vileid Uleberg Trond Maukon Henriksen Marit Jørgensen Anne Kjersti Bakken Tor Arvid Breland 《Plant and Soil》2006,282(1-2):165-182
In order to improve the basis for utilising nitrogen (N) fixed by white clover (Trifolium repens L.) in northern agriculture, we studied how defoliation stress affected the N contents of major plant organs in late autumn,
N losses during the winter and N accumulation in the following spring. Plants were established from stolon cuttings and transplanted
to pots that were dug into the field at Apelsvoll Research Centre (60°42′ N, 10°51′ E) and at Holt Research Centre (69°40′ N,
18°56′ E) in spring 2001 and 2002. During the first growing season, the plants were totally stripped of leaves down to the
stolon basis, cut at 4 cm height or left undisturbed. The plants were sampled destructively in late autumn, early spring the
second year and after 6 weeks of new spring growth. The plant material was sorted into leaves, stolons and roots. Defoliation
regime did not influence the total amount of leaf N harvested during and at the end of the first growing season. However,
for intensively defoliated plants, the repeated leaf removal and subsequent regrowth occurred at the expense of stolon and
root development and resulted in a 61–85% reduction in the total plant N present in late autumn and a 21–59% reduction in
total accumulation of plant N (plant N present in autumn + previously harvested leaf N). During the winter, the net N loss
from leaf tissue (N not recovered in living nor dead leaves in the spring) ranged from 57% to 74% of the N present in living
leaves in the autumn, while N stored in stolons and roots was much better conserved. However, the winter loss of stolon N
from severely defoliated plants (19%) was significantly larger than from leniently defoliated (12%) and non-defoliated plants
(6%). Moreover, the fraction of stolon N determined as dead in the spring was 63% for severely defoliated as compared to 14%
for non-defoliated plants. Accumulation in absolute terms of new leaf N during the spring was highly correlated to total plant
N in early spring (R2 = 0.86), but the growth rates relative to plant N present in early spring were not and, consequently, were similar for all
treatments. The amount of inorganic N in the soil after snowmelt and the N uptake in plant root simulator probes (PRSTM) during the spring were small, suggesting that microbial immobilisation, leaching and gas emissions may have been important
pathways for N lost from plant tissue. 相似文献
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Population structure, growth and body composition (wet-, dry-, ash weight and total lipid) of the Arctic pelagic amphipod Themisto libellula were studied in four fjords on West Spitsbergen, Svalbard, from July to December 2000 and in April 2002. In one of the fjords, Kongsfjorden, growth of T. libellula was calculated as the change in mean length of the 0+ cohort from July to December. The young were released from the brood pouches in early spring (March–April). Summer growth was 3.5 mm month−1, whereas growth during the autumn was only 0.6 mm month−1. The size frequency distributions indicated a 2–2.5 year life-span. The size structure of the population in Hornsund, the southernmost fjord on Spitsbergen, indicated a delayed time of spawning. The storage of lipids in T. libellula occurred during late summer and towards the winter, when the food items contain the maximum amount of stored lipids. 相似文献
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Knut H. Red Kjersti S. Kvie Robert J. Losey Pavel A. Kosintsev Anne K. Hufthammer Mark J. Dwyer Vasiliy Goncharov Konstantin B. Klokov Dmitry V. Arzyutov Andrei Plekhanov David G. Anderson 《Ecology and evolution》2020,10(17):9060-9072
Just as the domestication of livestock is often cited as a key element in the Neolithic transition to settled, the emergence of large‐scaled reindeer husbandry was a fundamental social transformation for the indigenous peoples of Arctic Eurasia. To better understand the history of reindeer domestication, and the genetic processes associated with the pastoral transition in the Eurasian Arctic, we analyzed archaeological and contemporary reindeer samples from Northwestern Siberia. The material represents Rangifer genealogies spanning from 15,000 years ago to the 18th century, as well as modern samples from the wild Ta?myr population and from domestic herds managed by Nenetses. The wild and the domestic population are the largest populations of their kind in Northern Eurasia, and some Nenetses hold their domestic reindeer beside their wild cousins. Our analyses of 197 modern and 223 ancient mitochondrial DNA sequences revealed two genetic clusters, which are interpreted as representing the gene pools of contemporary domestic and past wild reindeer. Among a total of 137 different mitochondrial haplotypes identified in both the modern and archaeological samples, only 21 were detected in the modern domestic gene pool, while 11 of these were absent from the wild gene pool. The significant temporal genetic shift that we associate with the pastoral transition suggests that the emergence and spread of reindeer pastoralism in Northwestern Siberia originated with the translocation and subsequent selective breeding of a special type of animal from outside the region. The distinct and persistent domestic characteristics of the haplotype structure since the 18th century suggests little genetic exchange since then. The absence of the typical domestic clade in modern nearby wild populations suggests that the contemporary Nenets domestic breed feature an ancestry from outside its present main distribution, possibly from further South. 相似文献
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Tina Rambrand Flemming Pociot Kjersti Rønningen Jørn Nerup B. K. Michelsen 《Human genetics》1997,99(2):177-185
Reliable genetic and immunological markers are important in the prediction of insulin-dependent diabetes mellitus (IDDM).
Since glutamic acid decarboxylase (GAD) is a candidate primary autoantigen, we examined the possible linkage between IDDM
and the genes encoding GAD65 (GAD2, 10p11–12) and GAD67 (GAD1, 2q31) in 58 Danish IDDM affected sib pairs. The allelic inheritance of 10 polymorphic dinucleotide repeat sequences spanning
the chromosomal regions of the two GAD genes, were examined by affected sib pair analysis (ASP). In addition a restriction
fragment length polymorphism (RFLP) was identified in the gene encoding GAD65 using the restriction enzyme PvuII. The GAD gene markers were analyzed in relation to the presence of specific HLA types and GAD autoantibodies. No evidence
of linkage was found between IDDM and either of the genes encoding GAD. This was also the case when subgroups carrying specific
HLA susceptibility alleles were analyzed. Nor did we observe any association between these GAD genetic markers and the presence
of GAD autoantibodies. Considering the high prevalence of GAD autoantibodies in IDDM, a putative genetic association between
GAD and IDDM would be expected to affect most diabetic individuals. Therefore, our data indicate that the association between
GAD and IDDM is not genetically determined, and that microsatellites used in this study do not contribute to the prediction
of IDDM.
Received: 1 July 1996 / Revised: 21 August 1996 相似文献
69.
Being abundant is not enough: a decrease in effective population size over eight generations in a Norwegian population of the seaweed, Fucus serratus
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The brown alga Fucus serratus is a key foundation species on rocky intertidal shores of northern Europe. We sampled the same population off the coast of southern Norway in 2000 and 2008, and using 26 microsatellite loci, we estimated the changes in genetic diversity and effective population size (Ne). The unexpectedly low Ne (73-386) and Ne/N ratio (10-3-10-4), in combination with a significant decrease (14%) in allelic richness over the 8-year period, suggests an increased local extinction risk. If small Ne proves to be a common feature of F. serratus, then being abundant may not be enough for the species to weather future environmental changes. 相似文献
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In developing bioassays for estrogenic effects, vitellogenin (Vtg) induction and zona radiata protein (Zr-protein) induction in males and juveniles of oviparous vertebrates have been used as sensitive biomarkers for estrogenicity.
Nonylphenol (NP) produces similar and parallel expression patterns of Vtg and Zr-protein levels in plasma and surface mucus of salmon, the response being concentration- and time-dependent. We have explored
the potential mechanisms of Vtg and Zr-protein expression in surface mucus by comparative molecular and cellular approaches. Liver, skin, blood, and surface mucus
samples were collected from fish exposed to a single waterborne concentration of NP (10 and 60 μg/l), 3, 7, and 10 days post-exposure,
for gene expression analysis (liver and skin; quantitative real-time polymerase chain reaction) and protein analysis (blood
and surface mucus; enzyme-linked immunosorbent assay). Protein expression was localized by immunohistochemistry. NP produced
concentration- and time-dependent increases of hepatic estrogen receptors (ERα and ERβ), Vtg, and Zr-protein mRNA and plasma protein levels. These responses paralleled cellular detection of Vtg and Zr-protein in the liver with unique expression patterns in the cytoplasm of hepatocytes, hepatic sinusoids, and endothelial
cells. ERα, Vtg, and Zr-protein mRNA were detectable in the skin. ERβ was the only skin response that was NP-concentration-dependent, especially
at day 10 post-exposure. Immunohistochemistry for Vtg and Zr-protein in skin showed unique expression patterns in mucus vacuoles, epidermal cells, and scales in an NP-concentration-
and time-specific manner. Thus, analysis of skin mRNA levels for xenoestrogen biomarker responses is a less-promising approach
than protein analysis. The immunohistochemical localization of Vtg and Zr-protein levels in the skin further validates surface mucus as a sensitive biomarker source for estrogenic compounds. These
responses represent an improvement for the detection of endocrine-disrupting compounds and related pollutants in the environment.
The Norwegian Research Council (NFR) financially supported this study. 相似文献