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1.
Sparse Ulmus pumila woodlands play an important role in contributing to ecosystem function in semi-arid grassland of northern China. To understand
the key attributes of soil carbon cycling in U. pumila woodland, we studied dynamics of soil respiration in the canopy field (i.e., the projected crown cover area) and the open
field at locations differing in distance (i.e., at 1–1.5, 3–4, 10, and >15 m) to tree stems from July through September of
2005, and measured soil biotic factors (e.g., fine root mass, soil microbial biomass, and activity) and abiotic factors [e.g.,
soil water content (SWC) and organic carbon] in mid-August. Soil respiration was further separated into root component and
microbial component at the end of the field measurement in September. Results showed that soil respiration had a significant
exponent relationship with soil temperature at 10-cm depth. The temperature sensitivity index of soil respiration, Q
10, was lower than the global average of 2.0, and declined significantly (P < 0.05) with distance. The rate of soil respiration was generally greater in the canopy field than in the open field; monthly
mean of soil respiration was 305.5–730.8 mg CO2 m−2 h−1 in the canopy field and 299.6–443.1 mg CO2 m−2 h−1 in the open field from July through September; basal soil respiration at 10°C declined with distance, and varied from ~250 mg
CO2 m−2 h−1 near tree stems to <200 mg CO2 m−2 h−1 in the open field. Variations in soil respiration with distance were consistent with patterns of SWC, fine root mass, microbial
biomass and activities. Regression analysis indicated that soil respiration was tightly coupled with microbial respiration
and only weakly related to root respiration. Overall, variations in SWC, soil nutrients, microbial biomass, and microbial
activity are largely responsible for the spatial heterogeneity of soil respiration in this semi-arid U. pumila woodland. 相似文献
2.
Guang-Chang Ma Hao-Yuan Hu Li-Ming Niu Yue-Guan Fu Zheng-Qiang Peng Wen-Jun Bu Da-Wei Huang 《Symbiosis (Philadelphia, Pa.)》2009,49(3):133-136
Figs (Ficus) are keystone resources that maintain tropical biodiversity. Pollinators, non-pollinating fig wasps, and some insects that
feed internally in syconia (the fruits of figs) synchronize their developmental stages with syconia. Other insects feed and
develop externally on the syconia but little is known about adaptations in these insects. We investigated the life cycle of
Elasmucha necopinata, a bug that develops externally on the syconia of Ficus hispida, a functionally dioecious fig. The bug oviposits about a week after fig receptivity, the nymphs feed externally on the syconia
and eclosion occurs when the syconia mature. Thus, nymphs synchronize their developmental stages with the male syconia of
F. hispida. Although the relationship does not appear to be mutualistic, we suggest that E. necopinata, feeding externally, has adapted to figs, in a similar way to Agaonid fig wasps that live internally. We believe that this
is the first direct evidence of adaptation of an externally feeding insect to figs. 相似文献
3.
Masaki Okuda Akihiro Sumida Hiroaki Ishii Valentina P. Vetrova Toshihiko Hara 《Ecological Research》2008,23(5):831-840
We investigated the spatial distribution and growth of the Siberian dwarf pine (Pinus pumila) in a valley–foothill larch–birch (Larix cajanderi–Betula platyphylla as canopy trees) mixed forest of fire origin located in central Kamchatka with the aim of elucidating the ecological features
of P. pumila when it is an undergrowth species in a forest. The spatial distribution of all individuals of all tree species was clumped,
and the spatial distribution of the two canopy tree species did not repulsively affect that of P. pumila (i.e., its establishment site). These results suggest that the regeneration of P. pumila does not depend on canopy gaps. However, the analysis using a growth model indicated that the canopy trees negatively affected
the growth of P. pumila and that the negative effect of L. cajanderi on P. pumila growth was stronger than that of B. platyphylla. The direction of the crown extension of P. pumila was weakly related to the open-space direction. Our results suggest that, although the spatial pattern of establishment of
P. pumila is not repulsed by the distribution of canopy trees, the crown can spread horizontally toward the more sparsely populated
areas of the canopy trees where they may have higher growth rates. 相似文献
4.
Citrus FT (CiFT) cDNA, which promoted the transition from the vegetative to the reproductive phase in Arabidopsis thaliana, when constitutively expressed was introduced into trifoliate orange (Poncirus trifoliata L. Raf.). The transgenic plants in which CiFT was expressed constitutively showed early flowering, fruiting, and characteristic morphological changes. They started to
flower as early as 12 weeks after transfer to a greenhouse, whereas wild-type plants usually have a long juvenile period of
several years. Most of the transgenic flowers developed on leafy inflorescences, apparently in place of thorns; however, wild-type
adult trifoliate orange usually develops solitary flowers in the axils of leaves. All of the transgenic lines accumulated
CiFT mRNA in their shoots, but there were variations in the accumulation level. The transgenic lines showed variation in phenotypes,
such as time to first flowering and tree shape. In F1 progeny obtained by crossing ‘Kiyomi’ tangor (C. unshiu × sinensis) with the pollen of one transgenic line, extremely early flowering immediately after germination was observed. The transgene
segregated in F1 progeny in a Mendelian fashion, with complete co-segregation of the transgene and the early flowering phenotype. These results
showed that constitutive expression of CiFT can reduce the generation time in trifoliate orange. 相似文献
5.
Since pollen usually travels limited distances in wind-pollinated plant species, plants growing at low density may become
pollen limited. We examined how local pollen availability and population density affect reproductive success in two wind-pollinated,
dioecious species, Thalictrum fendleri and Thalictrum dioicum. Distance to the nearest flowering male, the number of flowering males within 2 m, and flower number on those males served
as measures of local pollen availability. Increased distance from pollen donors reduced seed set in the lowest-density population
of each species, but seed set in high-density populations was not correlated with local pollen availability. For plants in
high- and low-density populations at similar distances from pollen donors, this distance only affected seed set in low-density
populations. To ensure that differences in resource availability were not causing spurious correlations between seed set and
plant density, we constructed low-density artificial arrays in populations of T. dioicum. In these, seed set decreased rapidly with increases in distance from pollen donors. Despite these effects, the density of
males in a population was not correlated with average seed set in T. dioicum, and hand pollination in the T. dioicum populations also failed to increase seed set over natural levels. These results suggest that pollen receipt only limits seed
set on isolated plants within low- density populations of T. dioicum and T. fendleri. 相似文献
6.
Post-pollination hybridization barriers in <Emphasis Type="Italic">Nicotiana</Emphasis> section <Emphasis Type="Italic">Alatae</Emphasis> 总被引:1,自引:1,他引:0
Christopher B. Lee Lawrence E. Page Bruce A. McClure Timothy P. Holtsford 《Sexual plant reproduction》2008,21(3):183-195
Nicotiana section Alatae contains eight species with variable flower sizes and morphologies. Section members readily hybridize in the glasshouse,
but no hybrids have been observed in natural sympatric and parapatric populations. To investigate interspecific crossing relationships
with respect to mechanisms preventing hybridization, all members of section Alatae were intercrossed in a complete diallel. We found positive correlation between the pistil length of the pollen donor and
interspecific seed set relative to the conspecific cross. Pollen tube growth rate and pollen donor pistil length were positively
correlated as well. Furthermore, pollen from short-pistil members of section Alatae could only grow a maximum distance proportional to, but greater than, their own pistil lengths. Our results show that pollen
tube growth capacity (i.e., rate and distance), provides a hybridization barrier in long-pistil species × short-pistil species
crosses. We also found another hybridization barrier not specifically related to pollen tube growth capacity in short-pistil
species × long-pistil species. Taken together, these barriers can generally be described by a ‘pistil-length mismatch’ rule;
in section Alatae, pollen has the most success fertilizing ovules from species with pistil lengths similar to their own. This rule could contribute
to hybridization barriers in Section Alatae because the species display dramatically different pistil lengths.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
7.
Erhard E. Pfündel 《Photosynthesis research》2009,100(3):163-177
The F
0 and F
M level fluorescence from a wild-type barley, a Chl b-less mutant barley, and a maize leaf was determined from 430 to 685 nm at 10 nm intervals using pulse amplitude-modulated
(PAM) fluorimetry. Variable wavelengths of the pulsed excitation light were achieved by passing the broadband emission of
a Xe flash lamp through a birefringent tunable optical filter. For the three leaf types, spectra of F
V/F
M (=(F
M − F
0)/F
M) have been derived: within each of the three spectra of F
V/F
M, statistically meaningful variations were detected. Also, at distinct wavelength regions, the F
V/F
M differed significantly between leaf types. From spectra of F
V/F
M, excitation spectra of PS I and PS II fluorescence were calculated using a model that considers PS I fluorescence to be constant
but variable PS II fluorescence. The photosystem spectra suggest that LHC II absorption results in high values of F
V/F
M between 470 and 490 nm in the two wild-type leaves but the absence of LHC II in the Chl b-less mutant barley leaf decreases the F
V/F
M at these wavelengths. All three leaves exhibited low values of F
V/F
M around 520 nm which was tentatively ascribed to light absorption by PS I-associated carotenoids. In the 550–650 nm region,
the F
V/F
M in the maize leaf was lower than in the barley wild-type leaf which is explained with higher light absorption by PS I in
maize, which is a NADP-ME C4 species, than in barley, a C3 species. Finally, low values of F
V/F
M at 685 in maize leaf and in the Chl b-less mutant barley leaf are in agreement with preferential PS I absorption at this wavelength. The potential use of spectra
of the F
V/F
M ratio to derive information on spectral absorption properties of PS I and PS II is discussed. 相似文献
8.
Understanding the patterns of contemporary, pollen-mediated gene flow is of great importance for designing appropriate conservation
strategies. In this study, ten novel polymorphic microsatellite loci were isolated for the rare dioecious tree, Eurycorymbus cavaleriei, and the patterns of pollen dispersal were investigated in an ex situ conserved population. A combination of microsatellite
markers with high-collective exclusion power (0.932) was used to assign paternity to 240 seeds collected from eight maternal
trees. The average effective pollen dispersal distance (δ) was 292.6 m and the frequency distribution of pollen movement suggested extensive pollen movement in the population. The
effective pollen donors per maternal tree (N
ep) ranged from 5 to 10, and the most isolated maternal trees were observed with the largest number of N
ep = 10. Although a trend of near-neighbor mating was found in seven of eight maternal trees, no significant correlations were
detected between the average effective pollen dispersal distance (δ) and the geographic distances (d1 and d2) between maternal and male trees. The increased average effective distance of pollen
dispersal and number of N
ep for isolated maternal trees might be a compound consequence of low density and long-distance flight of pollinators of this
species. The conservation implications of these results are discussed. 相似文献
9.
Shen Chen Zhanghui Huang Liexian Zeng Jianyuan Yang Qiongguang Liu Xiaoyuan Zhu 《Molecular breeding : new strategies in plant improvement》2008,22(3):433-441
Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a devastating disease in rice worldwide. The resistance gene Xa7, which provides dominant resistance against the pathogen with avirulence (Avr) gene AvrXa7, has proved to be durably resistant to BB. A set of SSR markers were selected from the “gramene” database based on the Xa7 gene initial mapping region on chromosome 6. These markers were used to construct a high-resolution genetic map of the chromosomal
region surrounding the Xa7 gene. An F2 mapping population with 721 highly susceptible individuals derived from a cross between the near isogenic lines (NILs) IRBB7
and IR24 were constructed to localize the Xa7 gene. In a primary analysis with eleven polymorphic SSR markers, Xa7 was located in approximately the 0.28-cM region. To walk closer to the target gene, recombinant F2 individuals were tested using newly developed STMS (sequence tagged microsatellite) markers. Finally, the Xa7 gene was mapped to a 0.21-cM interval between the markers GDSSR02 and RM20593. The Xa7-linked markers were landed on the reference sequence of cv. Nipponbare through bioinformatics analysis. A contig map corresponding
to the Xa7 gene was constructed. The target gene was assumed to span an interval of approximately 118.5-kb which contained a total of
fourteen genes released by the TIGR Genome Annotation Version 5.0. Candidate-gene analysis of Xa7 revealed that the fourteen genes encode novel domains that have no amino acid sequence similar to other cloned Xa(xa) genes.
Shen Chen and Zhanghui Huang are contributed equally to this work. 相似文献
10.
Xuesong Zhao Juan Wang Jie Li Ling Fu Juan Gao Xiuli Du Hongtao Bi Yifa Zhou Guihua Tai 《Journal of industrial microbiology & biotechnology》2009,36(5):721-726
Fourteen phytopathogenic fungi were tested for their ability to transform the major ginsenosides to the active minor ginsenoside
Rd. The transformation products were identified by TLC and HPLC, and their structures were assigned by NMR analysis. Cladosporium fulvum, a tomato pathogen, was found to transform major ginsenoside Rb1 to Rd as the sole product. The following optimum conditions for transforming Rd by C. fulvum were determined: the time of substrate addition, 24 h; substrate concentration, 0.25 mg ml−1; temperature, 37°C; pH 5.0; and biotransformation period, 8 days. At these optimum conditions, the maximum yield was 86%
(molar ratio). Further, a preparative scale transformation with C. fulvum was performed at a dose of 100 mg of Rb1 by a yield of 80%. This fungus has potential to be applied on the preparation for Rd in pharmaceutical industry. 相似文献
11.
Population fragmentation is often correlated with loss of genetic diversity and reduced fitness. Obligate out-crossing (dioecy)
is expected to enhance genetic diversity, reduce genetic differentiation, and avoid inbreeding depression through frequent
gene flow. However, in highly fragmented populations dioecy has only diminishing effects upon genetic structure as pollination
limitations (e.g. flight distance of pollinators) most often restrict inter-population gene flow in insect pollinated species.
In fragmented dry grasslands in northeastern Germany, we analysed genetic structure, fitness, and habitat quality of the endangered
dioecious Silene otites (Caryophyllaceae). Using AFLP markers, a high level of differentiation among ten populations was found (F
st = 0.36), while the intra-population genetic diversities (H
E = 0.165–0.240) were similar as compared to hermaphroditic species. There was neither a correlation between geographic and
genetic distance nor between genetic diversity and population size, which indicates reduced gene flow among populations and
random genetic drift. Plant size was positively correlated with genetic diversity. Seed set and number of juveniles were positively
related to population size. Higher total coverage resulted in reduced plant fitness, and the number of juveniles was negatively
correlated to cryptogam cover. Additionally, we found a sex ratio bias towards more male plants in larger populations. Overall,
our results indicate that on a regional geographic scale dioecy does not necessarily prevent genetic erosion in the case
of habitat fragmentation, especially in the absence of long distance seed and pollen dispersal capacity. 相似文献
12.
Summary
Linaria khalkhalensis Hamdi & Assadi is described as a new species from Azerbaijan and Guilan provinces (northern Iran), belonging to Linaria sect. Linaria. It is close to Linaria lineolata Boiss. and L. elymaitica (Boiss.) Kuprian., which it resembles in habit and vegetative features. However, floral and seed characters together with
a distinctive geographical distribution, warrant recognition at the species rank. An illustration of the new species, a distribution
map, scanning electron micrographs of seed and capsule surfaces, and an identification key are also included. 相似文献
13.
This paper discusses a number of experiments performed, involving the fusion by an electric field of mesophyll protoplasts
from Solanum tuberosum cv. Bintje, S. tuberosum dihaploid clones 243, 299 and the wild tuberous disease-resistant species S. bulbocastanum and S. pinnatisectum. Three fusion experiments (S. bulbocastanum + S. tuberosum dihaploid 243, S. pinnatisectum + S. tuberosum cv. Bintje and S. pinnatisectum + S. tuberosum dihaploid 299) yielded 542 calli, the 52 ones of which produced shoots. Obtained regenerants were estimated by the flow-cytometry (FC)
and RAPD analysis to determine hybrid plants.The utilisation of the FC as a useful method for detecting somatic hybrids is
also discussed in this paper. The combination S. bulbocastanum + S. tuberosum dihaploid 243 led to the creation of eight somatic hybrids, the combination S. pinnatisectum + S. tuberosum cv. Bintje yielded four somatic hybrids and the combination S. pinnatisectum + S. tuberosum dihaploid 299 resulted in no hybrid regenerants. Morphology in vitro, growth vigour and production of tuber-like structures
were evaluated in hybrid plants. Plants were transferred in vivo for further estimation (acclimatization, habitus evaluation
and tuberization ability). 相似文献
14.
Porphyra katadae Miura var. hemiphylla Tseng et T. J. Chang, a species distributed around the Liaodong and Shandong Peninsulas of China, produces gametophytes from late winter to early spring. These are monoecious with male and female reproductive tissues in distinct halves or sectors. Vegetative tissues from sectors expected to differentiate into sexual tissue were cultured in the laboratory. Male and female reproductive organs, as well as conchocelis and blades, were differentiated from these tissues. The male and female reproductive tissues were in patches and mixed on the cultured tissue pieces. This was quite different from the wild-type sectored individuals. The F1 conchospore germlings also produced monospores, carposporangia, spermatangia and conchocelis. These carposporangia and spermatangia were in patches and were mixed on the F1 fronds. The results imply that P. katadae var. hemiphylla is possibly sex-differentiated rather than sex-determined. This is the first report of such a dimorphic life history in the genus Porphyra. 相似文献
15.
Kun-dong Bai De-bao Liao De-bing Jiang Kun-fang Cao 《Trees - Structure and Function》2008,22(4):449-462
Photosynthetic induction times and photoinhibition in relation to simulated sunflecks (sudden increase of irradiance from
20 to 1,500 μmol m−2 s−1) were examined in leaves of co-occurring Fagus lucida (a deciduous tree) and Castanopsis lamontii (an evergreen tree) saplings grown either in a beech forest understory or in an adjacent open site during a late rainy season.
Two hypotheses were tested: (1) understory leaves would display faster photosynthetic induction times and greater photoinhibition
than open-grown leaves; and (2) evergreen species would have slower photosynthetic induction times and lighter photoinhibition
than deciduous species. Times to reach 90% of maximal CO2 assimilation rate (t
90%A
) and stomatal conductance
did not differ between species, but showed faster by 3–5 min in open-grown leaves than understory leaves due to higher initial
stomatal conductance (g
s
initial) and induction state 1 min into simulated sunflecks (IS1min) in the former. Our analysis across the published data on photosynthetic induction of 48 broad-leaved woody species again
revealed the negative correlations between t
90%A
and either g
s initial or IS1min, and the similarity of t
90%A
and between evergreen and deciduous species. Measurements of maximum PSII photochemical efficiency (F
v/F
m) indicated that photoinhibition occurred in saplings in any of the growth habitats during sunfleck-induced photosynthetic
induction. Despite no interspecific differences in the degree of photoinhibition, understory leaves of both species suffered
heavier photoinhibition than open-grown leaves, as indicated by a stronger decrease of F
v/F
m in the former. Dynamic changes in the quantum yields of PSII photochemistry and ΔpH- and xanthophyll-regulated thermal dissipation
and adjustments in the partitioning of electron flow between assimilative and non-assimilative processes were functional to
resist photoinhibition. However, such photoinhibition, together with stomatal and biochemical limitations, would decrease
carbon gain during simulated sunflecks, particularly in understory leaves. 相似文献
16.
Olga Rotreklová 《Biologia》2008,63(1):61-66
Two pollen stainability tests (Alexander’s stain and acetocarmine) were used to detect differences in pollen viability of
the sexual, apomictic and sterile plants of Hieracium subgen. Pilosella. In sexual taxa (Hieracium bauhini and H. densiflorum), the average stainability was 93.7–98.4%. Similarly high stainability (92.2–97.2%) was found in the apomictic Hieracium pilosellinum and in the majority of the apomictic populations (or plants) of the pentaploid and hexaploid H. bauhini. In some apomictic plants of Hieracium bauhini the average pollen stainability was 49.0–75.4%. The lowest pollen stainability was found in the sterile plants, i.e. the
triploid H. pistoriense (33.6%) and the pentaploid H. brachiatum (29.6%). 相似文献
17.
18.
Sumita Kumari Prabhjeet Singh Sneh L. Singla-Pareek Ashwani Pareek 《Molecular biotechnology》2009,42(2):195-204
19.
20.
Xue-zhu Du Xian-hong Ge Xing-cheng Yao Zhi-gang Zhao Zai-yun Li 《Plant cell reports》2009,28(7):1105-1113
Intertribal somatic hybrids between Brassica napus (2n = 38, AACC) and a dye and medicinal plant Isatis indigotica (2n = 14, II) were obtained by fusions of mesophyll protoplasts. From a total of 237 calli, only one symmetric hybrid (S2) and
five asymmetric hybrids (As1, As4, As6, As7 and As12) were established in the field. These hybrids showed some morphological
variations and had very low pollen fertility. Hybrids S2 and As1 possessed 2n = 52 (AACCII), the sum of the parental chromosomes, and As12 had 2n = 66 (possibly AACCIIII). Hybrids As4, As6 and As7 were mixoploids (2n = 48–62). Genomic in situ hybridization analysis revealed that pollen mother cells at diakinesis of As1 contained 26 bivalents
comprising 19 from B. napus and 7 from I. indigotica and mainly showed the segregation 26:26 at anaphase I (AI) with 7 I. indigotica chromosomes in each polar group. Four BC1 plants from As1 after pollinated by B. napus resembled mainly B. napus in morphology but also exhibited some characteristics from I. indigotica. These plants produced some seeds on selfing or pollination by B. napus. They had 2n = 45 (AACCI) and underwent pairing among the I. indigotica chromosomes and/or between the chromosomes of two parents at diakinesis. All hybrids mainly had the AFLP banding patterns
from the addition of two parents plus some alterations. B. napus contributed chloroplast genomes in majority of the hybrids but some also had from I. indigotica. Production of B. napus–I. indigotica additions would be of considerable importance for genome analysis and breeding. 相似文献