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排序方式: 共有79条查询结果,搜索用时 15 毫秒
1.
F. CROUTE D. DUPOUY J. P. CHARLEY J. P. SOLEILHAVOUP H. PLANEL 《The Journal of eukaryotic microbiology》1980,27(1):132-135
SYNOPSIS Catalase activity of Paramecium tetraurelia decreased during autogamy and recovered to normal 5 days later. Autogamy also caused changes in the ciliate's sensitivity to natural ionizing radiations—the decrease in cell growth rate previously described in shielded cultures did not occur when autogamous cells were used. Maximum effect of shielding was observed in 11-day-old postautogamous cells. the role of the catalase in the mechanism of natural irradiation effect is discussed. 相似文献
2.
Structural changes associated with corolla wilting may serve as a mechanism for effecting self-pollination. Low pollinator visitation, high seed production and a corolla that persists after anthesis indicates that Pedicularis dunniana is autogamous. Delayed autonomous self-pollination is facilitated by corolla wilting. Wilting of the upper lip (galea) brought the pollen laden anthers into contact with the stigma resulting in the deposition of self pollen on the stigma. The seed set of flowers either emasculated, or with restrained galeae thus preventing anthers brushing against the stigma, was significantly lower than that of open-pollinated flowers. This demonstrates that autogamy occurs in this species through corolla wilting. Germination experiments indicated that outcross seedlings were more vigorous than selfed seedlings as a result of inbreeding depression. It is likely that autogamy provides reproductive assurance for P. dunniana under conditions of pollinator scarcity. 相似文献
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Christian Parisod Samuel Neuenschwander Jerome Goudet Nadir Alvarez Roberto Guadagnuolo François Felber Nils Arrigo 《Molecular ecology》2014,23(20):5089-5101
Extensive gene flow between wheat (Triticum sp.) and several wild relatives of the genus Aegilops has recently been detected despite notoriously high levels of selfing in these species. Here, we assess and model the spread of wheat alleles into natural populations of the barbed goatgrass (Aegilops triuncialis), a wild wheat relative prevailing in the Mediterranean flora. Our sampling, based on an extensive survey of 31 Ae. triuncialis populations collected along a 60 km × 20 km area in southern Spain (Grazalema Mountain chain, Andalousia, totalling 458 specimens), is completed with 33 wheat cultivars representative of the European domesticated pool. All specimens were genotyped with amplified fragment length polymorphism with the aim of estimating wheat admixture levels in Ae. triuncialis populations. This survey first confirmed extensive hybridization and backcrossing of wheat into the wild species. We then used explicit modelling of populations and approximate Bayesian computation to estimate the selfing rate of Ae. triuncialis along with the magnitude, the tempo and the geographical distance over which wheat alleles introgress into Ae. triuncialis populations. These simulations confirmed that extensive introgression of wheat alleles (2.7 × 10?4 wheat immigrants for each Ae. triuncialis resident, at each generation) into Ae. triuncialis occurs despite a high selfing rate (Fis ≈ 1 and selfing rate = 97%). These results are discussed in the light of risks associated with the release of genetically modified wheat cultivars in Mediterranean agrosystems. 相似文献
5.
Qiuxia Wang Shicheng Shao Yuan Su Xueli Hu Yong Shen Dake Zhao 《Ecology and evolution》2019,9(22):12906-12914
Dendrobium wangliangii is an epiphytic orchid distributed in the Jinshajiang dry‐hot valley in Luquan County, Yunnan Province, China. Most Dendrobium spp. typically have a low fruit set, but this orchid shows a higher fruit set under natural conditions despite the lack of effective pollinators. The pollination biology of the critically endangered D. wangliangii was investigated in this study. A fruit set rate of 33.33 ± 4.71% was observed after bagging treatment in 2017 and a high fruit set rate (65.72 ± 4.44% in 2011; 50.79 ± 5.44% in 2017) was observed under natural conditions, indicating that D. wangliangii is characterized by spontaneous self‐pollination. The anther cap blocked the growing pollinium; thus, the pollinium slid down and reached the stigmatic cavity, leading to autogamous self‐pollination. Specifically, 51.50% of 162 unopened flowers (total 257 flowers) of this Dendrobium species under extreme water‐deficit conditions developed into fruits, suggesting the presence of cleistogamy in D. wangliangii. Here, cleistogamy may represent the primary mode of pollination for this orchid. Spontaneous self‐pollination and specific cleistogamous autogamy could represent major adaptions to the drought and pollinator‐scarce habitat in the Jinshajiang dry‐hot valley. 相似文献
6.
The mating system of flowering plant populations evolves through selection on genetically based phenotypic variation in floral traits. The physical separation of anthers and stigmas within flowers (herkogamy) is expected to be an important target of selection to limit self-fertilization. We investigated the pattern of phenotypic and genetic variation in herkogamy and its effect of self-fertilization in a broad sample of natural populations of Aquilegia canadensis, a species that is highly selfing despite strong inbreeding depression. Within natural populations, plants exhibit substantial phenotypic variation in herkogamy caused primarily by variation in pistil length rather than stamen length. Compared to other floral traits, herkogamy is much more variable and a greater proportion of variation is distributed among rather than within individuals. We tested for a genetic component of this marked phenotypic variation by growing naturally pollinated seed families from five populations in a common greenhouse environment. For three populations, we detected a significant variation in herkogamy among families, and a positive regression between parental herkogamy measured in the field and progeny herkogamy in the greenhouse, suggesting that there is often genetic variation in herkogamy within natural populations. We estimated levels of self-fertilization for groups of flowers that differed in herkogamy and show that, as expected, herkogamy was associated with reduced selfing in 13 of 19 populations. In six of these populations, we performed floral emasculations to show that this decrease in selfing is due to decreased autogamy (within-flower selfing), the mode of selfing that herkogamy should most directly influence. Taken together, these results suggest that increased herkogamy should be selected to reduce the production of low-quality selfed seed. The combination of high selfing and substantial genetic variation for herkogamy in A. canadensis is enigmatic, and reconciling this observation will require a more integrated analysis of how herkogamy influences not only self-fertilization, but also patterns of outcross pollen import and export. 相似文献
7.
Floral specialization for different pollinators and divergent use of the same pollinator among co‐occurring Impatiens species (Balsaminaceae) from Southeast Asia 下载免费PDF全文
Saroj Ruchisansakun Pornpimon Tangtorwongsakul Ruth J. Cozien Erik F. Smets FMLS Timotheüs van der Niet 《Botanical journal of the Linnean Society. Linnean Society of London》2016,181(4):651-666
Floral variation among closely related species is thought to often reflect differences in pollination systems. Flowers of the large genus Impatiens are characterized by extensive variation in colour, shape and size and in anther and stigma positioning, but studies of their pollination ecology are scarce and most lack a comparative context. Consequently, the function of floral diversity in Impatiens remains enigmatic. This study documents floral variation and pollination of seven co‐occurring Impatiens spp. in the Southeast Asian diversity hotspot. To assess whether floral trait variation reflects specialization for different pollination systems, we tested whether species depend on pollinators for reproduction, identified animals that visit flowers, determined whether these visitors play a role in pollination and quantified and compared key floral traits, including floral dimensions and nectar characteristics. Experimental exclusion of insects decreased fruit and seed set significantly for all species except I. muscicola, which also received almost no visits from animals. Most species received visits from several animals, including bees, birds, butterflies and hawkmoths, only a subset of which were effective pollinators. Impatiens psittacina, I. kerriae, I. racemosa and I. daraneenae were pollinated by bees, primarily Bombus haemorrhoidalis. Impatiens chiangdaoensis and I. santisukii had bimodal pollination systems which combined bee and lepidopteran pollination. Floral traits differed significantly among species with different pollination systems. Autogamous flowers were small and spurless, and did not produce nectar; bee‐pollinated flowers had short spurs and large floral chambers with a wide entrance; and bimodally bee‐ and lepidopteran‐pollinated species had long spurs and a small floral chamber with a narrow entrance. Nectar‐producing species with different pollination systems did not differ in nectar volume and sugar concentration. Despite the high frequency of bee pollination in co‐occurring species, individuals with a morphology suggestive of hybrid origin were rare. Variation in floral architecture, including various forms of corolla asymmetry, facilitates distinct, species‐specific pollen‐placement on visiting bees. Our results show that floral morphological diversity among Impatiens spp. is associated with both differences in functional pollinator groups and divergent use of the same pollinator. Non‐homologous mechanisms of floral asymmetry are consistent with repeated independent evolution, suggesting that competitive interactions among species with the same pollination system have been an important driver of floral variation among Impatiens spp. 相似文献
8.
JOÃO M.R.B.V. AGUIAR LUDMILA M. PANSARIN JAMES D. ACKERMAN EMERSON R. PANSARIN 《Plant Species Biology》2012,27(1):86-95
Geographical variation in the reproductive biology of widespread species often occurs at their distributional boundaries. We sought to determine whether such variation has occurred in an invasive orchid, Oeceoclades maculata, across its naturalized range. We compared its reproductive biology in a Brazilian population with that published for a population on the Caribbean island of Puerto Rico. In the state of São Paulo, O. maculata flowers between December and February, at the height of the rainy season. Similar fruit sets were observed in manual self (76%) and cross (70.4%) pollination treatments. The fruit set of plants protected from both pollinators and rainfall was 6.1%, whereas plants exposed only to rainfall had a fruit set of 41.4%, slightly less than the controls (48.3%). Like the Puerto Rico population, reproduction is primarily through rain‐assisted autogamy, but unlike observations made on the island, outcrossing can eventually occur. We observed two butterfly species (Heliconius ethilla narcaea and Heliconius erato phyllis) pollinating O. maculata. Secretory epidermal cells and trichomes of the spur lumen produced 0.7 µL of 25% (sucrose equivalents) nectar per flower each morning, which was stored in a dilated basal portion of the spur and reabsorbed by the afternoon. Thus, geographical variation in reproductive biology exists across the broad invasive range of O. maculata. 相似文献
9.
Pollen discounting and the evolution of selfing in Arenaria uniflora (caryophyllaceae) 总被引:1,自引:0,他引:1
Fishman L 《Evolution; international journal of organic evolution》2000,54(5):1558-1565
Although most models of mating system evolution assign a central role to the male transmission advantage of selfing genotypes, empirical data on the male fitness consequences of increased self-pollination are still uncommon. Here, I use measures of pollen import and export by focal plants in genotyped arrays to investigate the effects of floral morphology and pollination environment on self and outcross male function. Plants from an autogamous population of Arenaria uniflora (Caryophyllaceae) exhibit complete pollen discounting relative to closely related outcrossers, as do morphologically intermediate F1 hybrids between the two populations. However, the low cumulative male fitness of hybrids probably results from reduced pollen number or competitive ability, rather than a nonlinear relationship with floral morphology. When surrounded by selfers, plants from the outcrosser population self-fertilize at nearly the same rate as selfers (>80%), but have much lower self male fitness due to reduced fruit set. Because outcross siring success is also extremely low (<8%) in this treatment, these mate-limited outcrossers are at male fitness disadvantage to both pseudocleistogamous selfers and nonlimited outcrossers. The relative male fitness of plants with different mating systems appears dependent on the ecological context, as well as on morphological trade-offs. 相似文献
10.