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1.
H. Nybom 《Oecologia》1987,72(4):562-568
Summary Pseudogamous blackberry species are polyploid and usually exhibit meiotic irregularities causing severe reduction in pollen viability. When species means were compared, relative seed set was strongly correlated with the number of good pollen grains produced per flower divided by the number of ovules (good-pollen/ovule ratio).Partial correlation analysis for percentage viable pollen and relative seed set, controlling for good-pollen/ovule ratio, revealed an almost significant relationship, presumably because meiotic irregularities have a similar effect on both pollen viability and the viability of meiotically derived embryo sacs. Seed germination, on the other hand, showed no relationship with relative seed set or with pollen viability.The automatic selfing capacity exhibited by most of these blackberry species does not appear to be related to either pollen production or relative seed set. 相似文献
2.
Camilo L. Quarin 《Sexual plant reproduction》1999,11(6):331-335
It is generally accepted that most angiosperms require an accurate balance between maternal and paternal genome contribution
for endosperm development. The endosperm balance number (EBN) hypothesis postulates that each species has an effective number
which must be in a 2:1 maternal to paternal ratio for normal endosperm development and seed formation. The aim of this work
was to investigate the effect of different sources and ploidy levels of pollen donors on endosperm formation and seed production
of aposporous tetraploid (2n=4×=40) Paspalum notatum. Hand-emasculated spikelets of an apomictic 4× plant were dusted with pollen of 2×, 4×, 5×, 6× and 8× races of the same species;
3× and 4× races of a phylogenetically closely related species, P. cromyorrhizon; and 2× and 4× races of P. simplex, a species of a different subgenus. Experiments including self-pollination as well as emasculation without pollination were
conducted for controls. Results indicated that apomictic 4×P. notatum is a pseudogamous species with effective fertilization of the two unreduced (2n) polar nuclei by a reduced (n) sperm. Endosperm
development and seed production occurred independently of the species or the ploidy level of the pollen donor. However, seed
germination rates were significantly lower than in the self-pollinated control when the pollen donor was 3×P. cromyorrhizon or 2× and 4×P. simplex. Aposporous embryo sacs in Paspalum contribute to endosperm formation with two unreduced (2n) polar nuclei, while the male contribution is the same as in sexual
plants (n). Since sexual Paspalum plants fit the EBN hypothesis, the EBN insensitivity observed in apomictic plants might be a prerequisite for the spread
of pseudogamous apomixis. The EBN insensitivity could have arisen as an imprinting consequence of a high maternal genome contribution.
Received: 20 February 1998 / Revision accepted: 21 October 1998 相似文献
3.
We conducted an experiment in a natural population of Alstroemeria
aurea, a clonal perennial, to determine (1) if reproduction was resource limited, and (2) if fruits would be selectively filled
based on differences in pollination intensity when pollen loads were adequate for full seed set. Under these conditions, differences
in pollination intensity are unlikely to affect seed number, but could affect seed quality, providing an interesting test
of the gametophytic competition hypothesis. To test for resource limitation, percent fruit maturation, number of seeds per
fruit and average seed weight were compared to paired controls for ramets in which all but one fruit was removed. To test
the effect of pollination intensity on selective resource allocation, three types of pollination treatments were performed:
(1) all flowers of the single inflorescence received a low pollen load, (2) all flowers received a high pollen load, (3) alternate
flowers of the inflorescence received either a high or a low pollen load. We determined the percentage of fruit that reached
maturity, counted the number of seeds and ovules and calculated the average seed weight for all capsules in each treatment.
Resources appeared to limit reproduction in this population since seed number and weight were significantly higher than in
controls when competing capsules were removed. At the whole ramet level, a four fold difference in pollen loads had no significant
effect on any of the parameters measured. However, when pollination intensity varied within an inflorescence, the number of
seeds per fruit increased by about 10% in flowers that received the higher pollen load. We observed the same trend in each
of 2 years, but the increase was significant in only 1 year. The differences, although not great, were only slightly smaller
than when all competing fruits were removed, and were consistent with selective resource allocation based on pollination intensity
independent of seed set.
Received: 28 September 1997 / Accepted: 30 April 1998 相似文献
4.
Silva Palacios I Tormo Molina R Nuñoz Rodríguez AF 《International journal of biometeorology》2000,44(3):128-133
The daily pollen concentration in the atmosphere of Badajoz (SW Spain) was analysed over a 6-year period (1993–1998) using
a volumetric aerobiological trap. The results for the main pollination period are compared with the number of hours of wind
each day in the four quadrants: 1 (NE), 2 (SE), 3 (SW) and 4 (NW). The pollen source distribution allowed 16 pollen types
to be analysed as a function of their distribution in the four quadrants with respect to the location of the trap. Four of
them correspond to species growing in an irrigated farmland environment (Amaranthaceae-Chenopodiaceae, Plantago, Scirpus, and Typha), five to riparian and woodland species (Salix, Fraxinus, Alnus, Populus, and Eucalyptus), four to urban ornamentals (Ulmus, Arecaceae, Cupressaceae, and Casuarina), and three which include the most frequent pollen grains of widely distributed species (Poaceae, Quercus, and Olea). The results show that the distribution of the sources and the wind direction play a very major role in determining the
pollen concentration in the atmosphere when these sources are located in certain quadrants, and that the widely distributed
pollen sources show no relationship with wind direction. In some years the values of the correlations were not maintained,
which leads one to presume that, in order to draw significant conclusions and establish clear patterns of the influence of
wind direction, a continuous and more prolonged study will be required.
Received: 6 May 1999 / Revised: 30 March 2000 / Accepted: 31 March 2000 相似文献
5.
Randall J. Mitchell 《Oecologia》1997,109(3):382-388
The amount of pollen arriving on a flower can be an important determinant of seed production. I investigated the effect of
varying pollen loads on seed set of the perennial desert mustard Lesquerella fendleri. To do this, I quantified the dose response relationship between stigmatic pollen load and seed set per fruit using over
400 flowers from 13 greenhouse-grown plants. Seed set per fruit generally increased with pollen up to about 100 pollen grains,
then reached a plateau. A negative exponential regression of seed set on pollen load for the pooled data explained less than
10% of the observed variation in seeds per fruit. However, accounting for variation among individual plants in the dose-response
relationship increased explained variation to 40%, indicating that plants responded differently to the same amount of available
pollen. Plants varied little in the initial slope of the dose-response curve, but differed substantially in the asymptote,
which ranged from 3 to 16 seeds. This limit is not imposed by ovule number, and may instead result from variation among plants
in vigor, propensity to abort seeds, or in gender specialization. Such variation among plants in dose-response relationships
has important consequences for understanding pollination limitation and pollen competition.
Received: 29 January 1996 / Accepted: 6 August 1996 相似文献
6.
G. Werlemark 《Sexual plant reproduction》2000,12(6):353-359
All members of Rosa section Caninae, dogroses are polyploid and characterized by their unbalanced meiosis, which in most cases leads to a pronounced morphological
influence from the maternal parent. In a previous investigation on a pair of reciprocal crosses between two species in this
section, Rosa dumalis and R. rubiginosa (2n=35), nine offspring plants (approximately 10%) did not receive any of the 21 RAPD markers present in the respective pollen
parent. This was interpreted as a possible occurrence of apomixis. These nine plants have now been subjected to a further
study with additional markers. Thirteen new RAPD markers showed the same result as in the previous investigation: none of
the nine plants inherited any of the pollen donor markers. The reproducibility of the RAPD markers was checked by mixing DNA
samples to obtain a series of artificial hybrids between the two parent plants. Twelve RAPD markers gave the expected result,
whereas one marker appeared only 50% of the time. In addition, pollen viability, mean number of seeds per hip, mean seed weight,
and mean weight of fruit flesh per hip have been studied on the four progeny groups: R. dumalis×R. rubiginosa plants which received pollen donor markers (PM plants), R. dumalis×R. rubiginosa plants which did not receive any pollen donor markers (NPM plants), R. rubiginosa×R. dumalis PM plants and R. rubiginosa×R. dumalis NPM plants. A canonical discriminant analysis based on these four reproductive characters separated the four progeny groups.
There were significant differences between the two PM groups in all investigated characters, and also between the PM and the
NPM groups in pollen viability. The result from the RAPD markers together with the differences in pollen viability between
the PM and NPM progeny groups is taken as an indication that apomixis occurs within the Caninae section.
Received: 13 October 1999 / Revision accepted: 28 January 2000 相似文献
7.
Penetration of pollen tubes through stigmatic tissues in Brassica napus L. may involve the release of cell wall modifying enzymes from the pollen tube tip. We examined the expression of a pectin-degrading
polygalacturonase (PG) enzyme in unpollinated and early and late pollinated stigmas via immunoblotting and immuno-light microscopy
using a PG polyclonal antibody. Immunoblotting analysis indicated that PG enzyme was present at low levels in unpollinated
stigmas and at high levels in pollinated stigmas. The level of PG did not detectably increase between early and late pollinated
stigmas. Immuno-light microscopy demonstrated that PG enzyme was present in ungerminated pollen grains, stigmatic papillae
and in the tip of pollen tubes growing into the papillar wall. This latter evidence suggests that PG enzyme may play an important
role in papillar cell wall penetration during pollination although other interpretations of the role of pollen PG should not
be discounted.
Received: 9 November 2000 / Accepted: 7 December 2000 相似文献
8.
RAPD analysis: a method to investigate aspects of the reproductive biology of Hypericum perforatum L. 总被引:2,自引:0,他引:2
B. Arnholdt-Schmitt 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,100(6):906-911
Recent interest in breeding strategies for Hypericum perforatum L. requires a better understanding of the floral biology of this medicinal plant. The aim of the present study was to check,
whether RAPD fingerprinting may be a useful tool for research on the mode of reproduction of this species. Progenies from
three defined single plants of two accessions, as well as progenies from a random sample of seeds of a wild population, of
H. perforatum were characterized by RAPD analyses using six primers. The results obtained by DNA fingerprints indicate the predominance
of an identical mode of reproduction for this species, obviously due to apomixis. Nevertheless, non-identical reproduction
was evident as a minor effect in H. perforatum, as could be demonstrated by significant deviations in the RAPD fingerprints of progenies from one single plant. It is concluded
that RAPD fingerprint analysis is a suitable technique to discover identity or non-identity in H. perforatum populations. Therefore, RAPDs may be used in addition to cytological studies to confirm the mode of reproduction by apomixis
versus self-pollination, haploid parthenogenesis or cross-fertilization.
Received: 12. August 1999 / Accepted: 27 August 1999 相似文献
9.
We examined the influence of pollen competitive environment on pollen performance in Mirabilis
jalapa. We used the number of pollen grains and the number of pollen tubes per pistil as measures of pollen competition. Pollen
germination, pollen tube penetration into the style, and pollen tube growth rates were used as measures of pollen performance.
All three measures of pollen performance were affected by the competitive environment. Pollen germination was greatest at
intermediate pollen load sizes. The percentage of germinated pollen grains that penetrated the stigma and grew into the style
decreased with pollen load size. Pollen tube growth rate in the style was greater and more variable with larger numbers of
pollen tubes in the style. Controlling for the degree of selection at the stigma indicated that pollen-pollen or pollen-style
interactions were the likely causes of increased growth rates.
Received: 28 October 1996 / Revision accepted: 24 January 1997 相似文献
10.
Effects of habitat isolation on pollinator communities and seed set 总被引:28,自引:4,他引:28
Destruction and fragmentation of natural habitats is the major reason for the decreasing biodiversity in the agricultural
landscape. Loss of populations may negatively affect biotic interactions and ecosystem stability. Here we tested the hypothesis
that habitat fragmentation affects bee populations and thereby disrupts plant-pollinator interactions. We experimentally established
small ”habitat islands” of two self-incompatible, annual crucifers on eight calcareous grasslands and in the intensively managed
agricultural landscape at increasing distances (up to 1000 m) from these species-rich grasslands to measure effects of isolation
on both pollinator guilds and seed set, independently from patch size and density, resource availability and genetic erosion
of plant populations. Each habitat island consisted of four pots each with one plant of mustard (Sinapis arvensis) and radish (Raphanus sativus). Increasing isolation of the small habitat islands resulted in both decreased abundance and species richness of flower-visiting
bees (Hymenoptera: Apoidea). Mean body size of flower-visiting wild bees was larger on isolated than on nonisolated habitat
islands emphasizing the positive correlation of body size and foraging distance. Abundance of flower-visiting honeybees depended
on the distance from the nearest apiary. Abundance of other flower visitors such as hover flies did not change with increasing
isolation. Number of seeds per fruit and per plant decreased significantly with increasing distance from the nearest grassland
for both mustard and radish. Mean seed set per plant was halved at a distance of approximately 1000 m for mustard and at 250
m for radish. In accordance with expectations, seed set per plant was positively correlated with the number of flower-visiting
bees. We found no evidence for resource limitation in the case of mustard and only marginal effects for radish. We conclude
that habitat connectivity is essential to maintain not only abundant and diverse bee communities, but also plant-pollinator
interactions in economically important crops and endangered wild plants.
Received: 7 May 1999 / Accepted: 19 July 1999 相似文献
11.
We studied the effect of floral color change on long- and short-distance attraction of insect pollinators to the herb lungwort, Pulmonaria collina. Lungwort flowers change color with age from red to blue. Young red flowers had a significantly greater pollen and nectar
reward and were significantly more often unpollinated than old blue ones. Red and blue flowers both influenced long-distance
attractiveness of plants, defined as the number of insect approaches towards an individual plant. After reaching a plant,
flower visitors preferred to visit young red flowers. Therefore, short-distance attractiveness, defined as the number of flowers
visited successively on an individual plant, was influenced mainly by the number of young red flowers. The co-occurrence of
the change in reproductive ability, in amount of reward, and in flower color enabled lungwort plants to direct pollinators
to reproductive, highly rewarding red flowers. The data suggest that by maintaining changed flowers lungwort plants can increase
their long-distance attraction and simultaneously enhance the probability of flower visits to pre-changed flowers. Thus, we
propose floral color change as a mechanism that can increase the efficiency of pollen transfer to enhance plant fitness.
Received: 2 November 1998 / Accepted: 14 July 1999 相似文献
12.
S-RNases are implicated in both inter- and intra-specific pollen rejection in Nicotiana. At least two mechanisms contribute to S-RNase dependent rejection of pollen from self compatilble species such as Nicotiana plumbaginifolia and N. tabacum. Cloned S-RNases from self incompatible N. alata expressed in styles of self compatible N. tabacum cause rejection of N. tabacum pollen through a factor-independent mechanism. However, rejection of N. plumbaginifolia pollen occurs only when S-RNases are expressed in conjunction with non-S-RNase factors from N. alata (factor-dependent pollen rejection). Here, we compared the pollen rejection activity of four RNases in these two systems.
Recombinant RNase expression levels in the factor-dependent N. plumbaginifolia system were insufficient to cause pollen rejection. However, three S-RNases were active in the factor-independent N. tabacum pollen rejection system. This system shows the broadest specificity of any system so far examined. However, RNaseI from E. coli could not cause N. tabacum pollen rejection. Thus, RNase activity alone is not sufficient for pollen rejection. Our results suggest that S-RNases are
specially adapted to function in pollen rejection.
Received: 15 December 2000 / Accepted: 1 May 2001 相似文献
13.
We examined the effects of pollen competition (pollen load size) on sporophytic vigor and gametophytic performance in Cucurbita texana, a wild gourd, while controlling for alternative interpretations of the data. Under field conditions we compared the vigor
of progeny produced from large and small pollen loads and examined the in vitro performance of the pollen produced by the
progeny. We found that the progeny from large pollen loads germinated faster and had a greater reproductive output (male flowers
and fruits) than progeny produced from small pollen loads. In addition, we found that the pollen produced on plants derived
from large pollen loads grew faster in vitro than the pollen produced on plants derived from small pollen loads. These findings
indicate that pollen competition affects the performance of the resulting sporophytic generation and the microgametophytes
they produce.
Received: 26 January 1997 / Revision accepted: 25 June 1997 相似文献
14.
15.
From the predominantly aposporous Ranunculus cassubicus group, a subgroup of the R. auricomus complex, two species with both diploid and tetraploid cytodemes (R. cassubicifolius W. Koch and R. carpaticola Soó) were known. Nine population samples of both species have been analyzed for variation of ploidy levels and isozymes.
DNA image analysis showed that three populations of R. cassubicifolius from Bavaria and Salzburg are diploid, two from Lower Austria tetraploid. In R. carpaticola, two populations from Central Slovakia and one from Romania are diploid, one from northern Slovakia is hexaploid. The polyploid
populations had somewhat smaller C-values than expected from diploids. Ploidy levels are consistent within populations, contradicting
previous hypotheses that cycles of diploid-tetra-ploid-dihaploid apomictic individuals occur in natural populations of goldilocks.
Isozyme-allozyme analysis of nine polymorphic loci showed that individual variation and genetic measures of di-ploid and tetraploid
populations are equivalent to those of sexual taxa. Multiple allelism and unbalanced gene dosages in tetraploid R. cassubicifolius give evidence for autopolyploidy that is most probably of multiple origin. The observed excess of homozygotes and the high
diversity between populations in the diploid populations of R. cassubicifolius are most probably due to geographical isolation of population groups, that might have happened during the Würm glaciation
and might have promoted the separation of autotetraploids in the easternmost part of the distribution range. Genetic distance
values analyzed by UPGMA of all sexual populations separated the two taxa and the cytodemes within R. cassubicifolius. Multidimensional scaling of individuals (including the apomicts) based on a presence/absence matrix of alleles confirmed
this differentiation with an overlapping zone between R. cassubicifolius and R. carpaticola. The hexaploid R. carpaticola population showed reduced genotypic diversity, an increased number of heterozygotes and fixed heterozygosity as typical for
apomictic mode of reproduction. This population shared alleles of both species without any specific ones, multidimensional
scaling placed genotypes among R. cassubicifolius. Thus, the hexa-ploid apomicts might have originated from hybrids of R. cassubicifolius and R. carpaticola. In general, evolution of agamic lineages in the R. cassubicus complex might have been facilitated by autopoly-ploids, because they can provide a bridge between the reproductive systems
that are otherwise isolated by ploidy levels, and also a starting point for spontaneous origin of apomixis.
Received October 8, 2001; accepted May 10, 2002 Published online: November 7, 2002
Addresses of the authors: Elvia H?randl (E-mail: elvira.hoerandl@univie.ac.at), Department of Systematics and Evolution of
Higher Plants; Johann Greilhuber (E-mail: Johann.Greilhuber@univie. ac.at), Department of Systematic Karyology and Embryology
of Plants; both: Institute of Botany, University of Vienna, Rennweg 14, A-1030 Vienna, Austria. 相似文献
16.
The potential for and constraints on the evolution of compensatory ability in Asclepias syriaca 总被引:2,自引:0,他引:2
To investigate the potential for and constraints on the evolution of compensatory ability, we performed a greenhouse experiment
using Asclepias syriaca in which foliar damage and soil nutrient concentration were manipulated. Under low nutrient conditions, significant genetic
variation was detected for allocation patterns and for compensatory ability. Furthermore, resource allocation to storage was
positively, genetically correlated both with compensatory ability and biomass when damaged, the last two being positively,
genetically correlated with each other. Thus, in the low nutrient environment, compensatory ability via resource allocation
to storage provided greater biomass when damaged. A negative genetic correlation between compensatory ability and plant biomass
when undamaged suggests that this mechanism entailed an allocation cost, which would constrain the evolution of greater compensatory
ability when nutrients are limited. Under high nutrient conditions, neither compensatory ability nor allocation patterns predicted
biomass when damaged, even though genetic variation in compensatory ability existed. Instead, plant biomass when undamaged
predicted biomass when damaged. The differences in outcomes between the two nutrient treatments highlight the importance of
considering the possible range of environmental conditions that a genotype may experience. Furthermore, traits that conferred
compensatory ability did not necessarily contribute to biomass when damaged, demonstrating that it is critical to examine
both compensatory ability and biomass when damaged to determine whether selection by herbivores can favor the evolution of
increased compensation.
Received: 2 April 1999 / Accepted: 21 September 1999 相似文献
17.
E. M. Lord 《Sexual plant reproduction》2001,14(1-2):57-62
Adhesion occurs both between pollen tubes and between the pollen tube and transmitting tract epidermis (TTE) in lily. The
stylar matrix secreted by the TTE can be isolated and used in an in vitro adhesion assay for pollen tubes. This bioassay was
used to isolate two stigma/stylar adhesion molecules in lily: a pectic polysaccharide and a small cysteine-rich, basic protein
we named SCA (stigma/stylar cysteine-rich adhesin). Both molecules were purified and used in an adhesion assay. Adhesion in
the assay can be disrupted by treatment of the pectin with polygalacturonase and of SCA with proteinase K. The two molecules
bind to each other in a pH-dependent fashion, and this binding is necessary for the adhesion assay to work. Antibodies to
each of the molecules show their localization at the sites of pollen tube adhesion in the style. Pollen does not produce SCA
but does bind this protein in vivo and in vitro. In vivo functional analyses are necessary to establish the roles of these
molecules in lily pollination.
Received: 29 October 2000 / Accepted: 17 April 2001 相似文献
18.
A. Rottenberg 《Sexual plant reproduction》2000,12(4):219-221
Exceptional, very rare, bisexual (hermaphroditic or monoecious) individuals have been detected in strictly dioecious populations
of Rhamnus alaternus, R. palaestinus, Bryonia syriaca and Populus euphratica (a single individual in each species). While ordinary male plants in each species exhibited fully normal pollen, and female
individuals set a considerable amount of fruit, the exceptional bisexual plants showed a reduction in male or female fertility,
or both. This inability of the rare bisexual individuals to fully invest in the two genders suggests that trade-offs between
male and female functions possibly play a major role in the breeding systems of these dioecious species, and probably implicates
resource allocation (among other factors) as a selective force in the evolution of dioecy.
Received: 5 April 1999 / Revision accepted: 30 June 1999 相似文献
19.
A recent literature review indicates that pollen limitation of female fertility is a common feature of flowering plants. Despite
the ecological and evolutionary significance of pollen limitation, most studies have only examined fertility in a single population
at one time. Here we investigate pollen limitation of fruit and seed set in five populations of Narcissus assoanus, a self- sterile, insect-pollinated geophyte, over 2–3 years in southern France. In common with many early spring flowering
plants, pollinator visitation to N. assoanus is often infrequent. Supplemental hand-pollination of flowers with outcross pollen significantly increased overall fruit
and seed set by 11% and 19%, respectively. Four of the five populations experienced some pollen limitation during the study.
For a given year, there was significant variation in pollen limitation among populations. Two of the populations were pollen
limited in one year but not in other years in which they were studied. Seed:ovule ratios for open- and hand-pollinated flowers
averaged 0.29 and 0.33, respectively. While hand pollination significantly increased the seed:ovule ratio, the low value obtained
indicates that the majority of ovules in flowers do not mature seeds despite hand pollination. The role of genetic and environmental
factors governing low seed:ovule ratios in N. assoanus is discussed.
Received: 28 December 1999 / Accepted: 6 April 2000 相似文献
20.
Survival and reproductive rate of mites in relation to resistance of their barn swallow hosts 总被引:2,自引:0,他引:2
A. P. Møller 《Oecologia》2000,124(3):351-357
Parasite resistance may act via a number of different mechanisms that regulate or control the survival and the reproductive
rate of parasites. Observations and experiments were used to test for effects of host resistance on parasite survival and
rate of reproduction. Natural levels of infestation of barn swallow Hirundo rustica nests by the tropical fowl mite Ornithonyssus bursa were positively related to brood size, inversely related to the length of the outermost tail feathers of male nest owners
(a secondary sexual character) and affected by time of reproduction by the host. A mite inoculation experiment, in which 50
adult mites were introduced into nests during the laying period of the host, was used to test for differential survival and
reproduction of mites as a function of host resistance. The relationship between survival and reproduction of parasites, male
tail length and host resistance was investigated. There was a negative relationship between mite numbers per nest after fledging
of nestlings and male tail length. This relationship was mainly caused by a reduction in the number of mites in the first
and second nymph stage with increasing tail length of male hosts, implying a reduction in rate of reproduction of mites. The
proportion of mites that had recently fed was inversely related to tail length of male hosts. The proportion of nymph stages
was positively related to the proportion of mites that had recently had a blood meal. Parasite resistance of barn swallows
to the tropical fowl mite thus appeared to act through increased mortality rate of adult and nymph stages of mites, and through
reduced reproductive rates of mites on resistant hosts. This is the first study demonstating a direct relationship between
fitness components of a parasite and the expression of a secondary sexual character of a host.
Received: 11 January 2000 / Accepted: 22 March 2000 相似文献