自引率: 3.2%
被引量: 5253
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审稿周期: 3
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Published by Thieme Medical Publishers. ISSN: 1435-8603.<br> Plant Biology is an international journal of the broadest scope bringing together the different subdisciplines of plant science, such as physi
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Comparative seed germination traits in alpine and subalpine grasslands: higher elevations are associated with warmer germination temperatures.
Seed germination traits in alpine grasslands are poorly understood, despite the sensitivity of these communities to climate change. We hypothesise that germination traits predict species occurrence along the alpine-subalpine elevation gradient. Phylogenetic comparative analyses were performed using fresh seeds of 22 species from alpine and subalpine grasslands (1600-2400 m) of the Cantabrian Mountains, Spain (43° N, 5° W). Laboratory experiments were conducted to characterise germinability, optimum germination temperature and effect of cold and warm stratification on dormancy breaking. Variability in these traits was reduced by phylogenetic principal component analysis (phyl.PCA). Phylogenetic generalised least squares regression (PGLS) was used to fit a model in which species average elevation was predicted from their position on the PCA axes. Most subalpine species germinated in snow-like conditions, whereas most alpine species needed accumulation of warm temperatures. Phylogenetic signal was low. PCA1 ordered species according to overall germinability, whilst PCA2 ordered them according to preference for warm or cold germination. PCA2 significantly predicted species occurrence in the alpine-subalpine gradient, as higher elevation species tended to have warmer germination preferences. Our results show that germination traits in high-mountain grasslands are closely linked to the alpine-subalpine gradient. Alpine species, especially those from stripped and wind-edge communities, prefer warmer germination niches, suggesting that summer emergence prevents frost damage during seedling establishment. In contrast, alpine snowfield and subalpine grassland plants have cold germination niches, indicating that winter emergence may occur under snow to avoid drought stress.
被引量：6 发表：1970
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Local climate explains degree of seed dormancy in Hypericum elodes L. (Hypericaceae).
Seed dormancy and germination characteristics may vary within species in response to several factors. Knowledge of such variation is crucial to understand plant evolution and adaptation to environmental changes. We examined the correlation of climate and population genetic differentiation (ISSR) with primary seed dormancy and germination behaviour in populations of the Atlantic-European soft-water pool specialist Hypericum elodes. Primary dormancy was measured by analysing seed germination response of fresh seeds and after various periods of cold stratification. Laboratory germination experiments revealed that the single most important factor for promoting germination was cold stratification prior to placing at the germination temperature. However, in agreement with their weaker primary dormancy, the seeds germinated well when fresh, and the benefit of cold stratification was more relaxed for the southern populations. Seeds of all populations demonstrated a near absolute requirement for a light and alternating temperature regime in order to germinate. The promoting effect of alternating temperatures was particularly effective at warm temperatures (mean 20 °C) but not at cool temperatures. Whilst seed germination requirements were similar among populations, the degree of primary dormancy varied considerably and was not associated with population genetic differentiation. Primary dormancy degree was instead associated with local climate: higher temperature in summer and rainfall in winter predicted weak and rapid loss of dormancy. These results suggest that seed maturation environment may play a substantial role in explaining the degree of dormancy in H. elodes, highlighting that physiological dormancy can be modulated by local climate.
被引量：7 发表：1970
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Effects of the duration of cold stratification on early life stages of the Mediterranean alpine plant Silene ciliata.
Cold stratification provided by snow cover is essential to break seed dormancy in many alpine plant species. The forecast reduction in snow precipitation and snow cover duration in most temperate mountains as a result of global warming could threaten alpine plant populations, especially those at the edge of their species distribution, by altering the dynamics of early life stages. We simulated some effects of a reduction in the snow cover period by manipulating the duration of cold stratification in seeds of Silene ciliata, a Mediterranean alpine specialist. Seeds from three populations distributed along an altitudinal gradient were exposed to different periods of cold stratification (2, 4 and 6 months) in the laboratory and then moved to common garden conditions in a greenhouse. The duration of the cold stratification treatment and population origin significantly affected seed emergence percentage, emergence rate and seedling size, but not the number of seedling leaves. The 6-month and 4-month cold stratification treatments produced higher emergence percentages and faster emergence rates than seeds without cold stratification treatment. No significant cold stratification duration x seed population origin interactions were found, thus differential sensitivity to cold stratification along elevation is not supported.
被引量：6 发表：1970
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Characterization of resistance gene analogs with a nucleotide binding site isolated from a triploid white poplar.
The majority of cloned plant disease resistance genes (R genes) encode a nucleotide binding site (NBS) and a leucine-rich repeat (LRR) domain. In this study, to better understand the R genes in white poplar, 59 resistance gene analogues (RGAs) were identified from a triploid white poplar [(Populus tomentosa x Populus bolleana) x P. tomentosa], based on conserved NBS regions. The 59 RGAs were phylogenetically classified into 10 subfamilies, and 54 RGAs with open-reading frames (ORFs) were further grouped into two classes, toll and interleukin-1 receptor (TIR) and non-TIR. BLAST searches with reference to the genomic sequence of Populus trichocarpa found 96 highly homologous regions distributed in 37 loci, suggesting the abundance and divergence of NBS-encoding genes in the triploid poplar genome. Within subfamilies 1-3, the average non-synonymous/synonymous substitution (omega) rates were < 1, indicating purifying selection on these RGAs, but some sites were clearly under diversifying selection with omega > 1. Many intergenic exchanges were also detected among these RGAs, indicating a probable role in homogenising NBS domains. Quantitative real-time PCR analysis revealed dramatic variations in the transcript level of 18 RGAs in the mature leaves, bark and roots of the triploid poplar, and identified two RGAs that had significantly higher level of transcripts in bark, four RGAs in mature leaves, and 14 in the above-ground portion of poplars, suggesting their probable roles in resistance against diseases attacking the organs. Our results shed light on genetic resources of poplar resistance and will be useful for further resistance gene isolation and exploitation.
被引量：- 发表：2008
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Smallest angiosperm genomes found in lentibulariaceae, with chromosomes of bacterial size.
Nuclear holoploid genome sizes (C-values) have been estimated to vary about 800-fold in angiosperms, with the smallest established 1C-value of 157 Mbp recorded in Arabidopsis thaliana. In the highly specialized carnivorous family Lentibulariaceae now three taxa have been found that exhibit significantly lower values: Genlisea margaretae with 63 Mbp, G. aurea with 64 Mbp, and Utricularia gibba with 88 Mbp. The smallest mitotic anaphase chromatids in G. aurea have 2.1 Mbp and are thus of bacterial size (NB: E. coli has ca. 4 Mbp). Several Utricularia species range somewhat lower than A. thaliana or are similar in genome size. The highest 1C-value known from species of Lentibulariaceae was found in Genlisea hispidula with 1510 Mbp, and results in about 24-fold variation for Genlisea and the Lentibulariaceae. Taking into account these new measurements, genome size variation in angiosperms is now almost 2000-fold. Genlisea and Utricularia are plants with terminal positions in the phylogeny of the eudicots, so that the findings are relevant for the understanding of genome miniaturization. Moreover, the Genlisea-Utricularia clade exhibits one of the highest mutational rates in several genomic regions in angiosperms, what may be linked to specialized patterns of genome evolution. Ultrasmall genomes have not been found in Pinguicula, which is the sister group of the Genlisea-Utricularia clade, and which does not show accelerated mutational rates. C-values in Pinguicula varied only 1.7-fold from 487 to 829 Mbp.
被引量：71 发表：2006
