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Quantifying the relative contribution of multiple isolation barriers to gene flow between recently diverged species is essential for understanding speciation processes. In parapatric populations, local adaptation is thought to be a major contributor to the evolution of reproductive isolation. However, extrinsic postzygotic barriers assessed in reciprocal transplant experiments are often neglected in empirical assessments of multiple isolation barriers. We analyzed multiple isolation barriers between two closely related species of the plant genus Dianthus, a genus characterized by the most rapid species diversification in plants reported so far. Although D. carthusianorum L. and D. sylvestris Wulf. can easily be hybridized in crossing experiments, natural hybrids are rare. We found that in parapatry, pollinator‐mediated prezygotic reproductive isolation barriers are important for both D. carthusianorum (0.761) and D. sylvestris (0.468). In contrast to D. carthusianorum, high hybrid viability in D. sylvestris (–0.491) was counteracted by strong extrinsic postzygotic isolation (0.900). Our study highlights the importance of including reciprocal transplant experiments for documenting extrinsic postzygotic isolation and demonstrates clearly divergent strategies and hence asymmetric pre‐ and postzygotic reproductive isolation between closely related species. It also suggests that pollinator‐mediated and ecological isolation could have interacted in synergistic ways, further stimulating rapid speciation in Dianthus.  相似文献   

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The study was aimed to examine the effects of soil amendment with organic waste materials on the growth of red fescue and the uptake of Cu and Zn by this grass, in view of its potential usage for phytostabilization of Cu-polluted soils. Five soils, containing 301–5180 mg/kg Cu, were collected from the surroundings of copper smelter Legnica, and amended with lignite (LG) and limed sewage sludge (SS). Plant growth and the concentrations of Cu and Zn in the shoots and roots of grass were measured in a pot experiment and related to the results of Pytotoxkit and Microtox® tests performed on soil solution. The effects of soil amendment with LG and SS differed greatly, and depended on soil properties. In some cases, the application of alkaline SS resulted in dramatic increase of Cu phytotoxicity and its enhanced uptake by plants, while application of LG to slightly acidic soil caused increased accumulation of Zn in plants, particularly in their roots. The study confirmed good suitability of red fescue for phytostabilization of Cu-contaminated soils except for those extremely polluted. Organic amendments to be used for metal immobilization should be thoroughly examined prior to application.  相似文献   

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When landscapes are heavily impacted by biological invasion, local populations of native plant species may no longer be adapted to altered environmental conditions. In these cases, it is useful to investigate alternative sources of germplasm, such as cultivated varieties, for planting at restoration sites. This study compared cultivated and wild (local) varieties of the native perennial bunchgrass, Poa secunda J. Presl, grown with and without the exotic, invasive Bromus tectorum L. in a greenhouse setting. While P. secunda cultivars emerged and grew more rapidly than wild seed sources, this advantage declined in the presence of B. tectorum and cultivated germplasm did not outperform wild accessions in the presence of an invasive species. Given the novel genetic background of cultivars and their potential to alter patterns of dominance in native plant communities, we recommend the use of local or regional wild seed sources when possible to conserve regional patterns of genetic diversity and adaptation. Use of multiple seed sources may increase the potential for capturing vigorous genotypes in the restoration seed mix. In cases where sites are heavily impacted by exotic, invasive species, other control measures will be necessary to improve establishment of native species in grassland restoration programs.  相似文献   

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Knowledge of pollination services provided by flower visitors is a prerequisite for understanding (co)evolutionary processes between plants and their pollinators, for evaluating the degree of specialization in the pollination system, and for assessing threats from a potential pollination crisis. This study examined pollination efficiency and visitation frequency of pollinators--key traits of pollinator-mediated fecundity--in a natural population of the wild carnation Dianthus carthusianorum. The five lepidopteran pollinator species observed differed in pollination efficiency and visitation frequency. Pollinator importance, the product of pollination efficiency and visitation frequency, was determined by the pollinator's visitation frequency. Pollination of D. carthusianorum depended essentially on only two of the five recorded pollinator species. Seed set was pollen-limited and followed a saturating dose-response function with a threshold of c. 50 deposited pollen grains for fruit development. Our results confirm that D. carthusianorum is specialized to lepidopteran pollinators, but is not particularly adapted to the two main pollinator species identified. The local persistence of D. carthusianorum is likely to be at risk as its reproduction depends essentially on only two of the locally abundant, but generally vulnerable, butterfly species.  相似文献   

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用能值分析辅以生理指标测定研究狐毛草的耐盐性   总被引:4,自引:0,他引:4  
狐毛草(Festucarubra)系羊茅属,禾本科,广布于温带和寒带地区,我国以西南最盛,大部分供饲料用。有关植物对重金属毒害和抗性的研究[1]揭示,狐毛草能在很高浓度(500μg·g-1)的铬溶液和较高浓度(100μg·g-1)的铜溶液中存活,可见狐毛草在消除重金属毒害和有机废物的环境生态工程中有很好的应用前景。同时,根据南京大学生物技术研究所引种海滩耐盐经济植物的经验,狐毛草是继大米草和互花米草之后的又一优良的耐盐经济植物,因此,对其抗性生理的研究是十分必要的。本文运用能值分析方法对试验结果进行分析处理。能值分析理论和…  相似文献   

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麻密  曾永强 《Acta Botanica Sinica》1997,39(11):1078-1081
重金属对生命机体的作用具有双重性。一方面,作为多数辅酶的辅助因子对细胞的正常代谢必不可少;另一方面,当重金属超过一定的浓度时对细胞有较大的毒性。在长期的进化过程中,生物可能形成一种调节细胞内重金属浓度的机制。这种机制在动物和真菌中被认为同金属硫蛋白(metallothionein,MT)的作用密切相关。植物中也存在类似的与重金属结合的低分子量蛋白(heavy metal binding pep-tide)。最近对拟南芥菜和水稻中类金属硫蛋白(MT-like)基因的研究证实其作用与动物MT相似。紫羊茅品种“Merlin”是一种从锌铅矿区的重金属污染地采集的单子叶草种,对镉和铜的抗性都较高,分别达到50mg/L和30mg/L,而5mg/L Cd~(2 )或2mg/L Cu~(2 )便可抑制敏感品种“S59”的正常生长。目前  相似文献   

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高羊茅和其他羊茅植株再生与遗传转化研究进展   总被引:10,自引:0,他引:10  
高羊茅、紫羊茅和草地羊茅均为很重要的多年生冷季型牧草与草坪草,生物技术在其品种改良中具有很大的应用潜力.30年来,三种羊茅的组织培养、胚性培养物的长期保存以及遗传转化等研究取得了较大进展,已建立起多种植株再生体系和遗传转化技术,但作为单子叶植物,这些草种的组织培养和转基因遗传改良也还存在一些问题.本文就以上几方面的内容进行了综述.  相似文献   

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 Highly regenerative tissues of tall fescue and red fescue produced from mature seed-derived embryogenic callus were induced and proliferated on medium containing 2,4-dichlorophenoxyacetic acid (4.5 or 9.0 μM), 6-benzylaminopurine (0, 0.044, 0.44 or 2.2 μM) and cupric sulfate (0.1 or 5.0 μM) under dim-light conditions (10 to 30 μE m–2 s–1, 16 h light). Tall fescue tissues were transformed with three plasmids containing the genes for hygromycin phosphotransferase (hpt), phosphinothricin acetyltransferase (bar) and β-glucuronidase (uidA;gus), and red fescue with three plasmids containing hpt, uidA and a synthetic green fluorescent protein gene [sgfp(S65T)]. DNA from T0 plants of eight independently transformed lines from tall fescue and 11 from red fescue were analyzed by PCR and DNA blot hybridization. The co-expression frequency of all three transgenes [hpt/bar/uidA or hpt/uidA/sgfp(S65T)] in transgenic tall fescue and red fescue plants was 25–27%; for two transgenes [hpt/bar or hpt/uidA for tall fescue and hpt/uidA or hpt/sgfp(S65T) for red fescue], the co-expression frequency was 50–75%. Received: 28 September 1999 / Revision received: 13 March 2000 / Accepted: 16 March 2000  相似文献   

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Zinc-induced vacuolation in root meristematic cells of Festuca rubra L.   总被引:3,自引:1,他引:3  
Abstract. The effect of Zn on vacuole development in root meristematic cells was examined in three cultivars of Festuca rubra: a Zn-tolerant cultivar (Merlin), a salt-tolerant cultivar (Hawk) and a non-tolerant cultivar (S.59) in order to determine whether or not vacuole development was related to Zn tolerance. Treatment with Zn greatly increased the percentage of cells in the apical meristem which were vacuolated in all three cultivars (7.01-fold increase in Merlin, 3.61-fold increase in Hawk and 5.39-fold increase in S.59 over the range 0–0.5 μg Zn cm?3). Morphometric analyses on electromicrographs indicated that the percentage total vacuolar volume fraction of meristematic tissue was also increased by Zn treatment. Most of this increase was due to an increase in a particular component of the vacuole which was 0.2–0.5 μm in diameter, spherical or ovoid in outline and possessed a distinct amorphous electron dense matrix (Type A intravacuolar body). X-ray microanalysis revealed that this matrix was rich in calcium and phosphorus in control plants. In Zn-treated roots, elevated levels of Zn were found in the matrix in Merlin and Hawk, but not in S.59. In addition, intravacuolar membranous whorls or myelin bodies were more highly organized in Zn-treated Merlin and Hawk but not S.59. Elevated Zn levels were not found in any other vacuolar component nor in nuclei, nucleoli, cell walls or ground cytoplasm. Control roots of Merlin possessed a greater type A vacuolar volume fraction than either Hawk or S.59 which may confer a greater capacity to compartmentalize Zn at the onset of exposure to toxic metals than the other cultivars. Predictably, the EM procedures resulted in loss of Zn from the roots to the fixative and dehydrating solutions. However, the rate of loss was the same (approximately 75–80%) regardless of cultivar. These findings are discussed in relation to their possible role in the mechanisms of Zn tolerance in these cultivars.  相似文献   

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  总被引:2,自引:0,他引:2  
The deposition of organic compounds from plant roots is a key determinant of rhizosphere microbial activity and community structure. Consequently, C-flow from roots to soil is an important process in coupling plant and microbial productivity, via impacts on microbial nutrient cycling in soil. Experimentally, isotopic tracers (13C or 14C) are used to track C inputs to soil and microbial communities. However, in many such studies the relationship between labelled C-flows and total C-flows are not established, limiting the interpretative value of the results. In this study, we applied steady-state near natural abundance 13CO2 labelling to determine the impact of partial defoliation of Festuca rubra on root exudation. This approach in axenic culture facilitated determination of the contribution of pre- and post-defoliation assimilates both to root C-flow and plant tissues. The results demonstrated that total root exudation was increased in the two days following defoliation. This was concurrent with reduced net CO2 assimilation and reduced allocation of post-defoliation assimilates below-ground and to active root meristems. Through determination of the δ13C of root exudates, it was established that the source of the increased root exudation was pre-defoliation assimilate. However, this response was transient, with reduced deposition of pre- and post-defoliation assimilates from roots during the period 2–4 d following defoliation. The results highlight the limitations of pulse-labelling approaches as a means of quantifying impacts of treatments on root exudation, particularly where the treatment is likely to affect plant C-partitioning or the balance between deposition to, and re-mobilization from, C-storage pools.  相似文献   

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A critical concern in the debate over the importance of sexual selection in plants is whether the nonrandom mating demonstrable in greenhouse crosses can occur in the field. Field populations likely experience smaller and more variable pollen load sizes than those that have been used in many greenhouse experiments. Therefore, we performed a greenhouse experiment in which we varied both pollen load size and composition in wild radish, Raphanus sativus, and examined the paternity of seeds. We used five maternal plants and four pairs of pollen donors. We were able to produce pollen loads of 40, 118, and 258 grains per stigma. The smallest of the pollen loads was scant enough to result in a slight, but significant reduction in seed number per fruit. While variation in pollen load composition significantly affected the proportions of seeds fathered by different donors, variation in pollen load size did not. The relative performance of different donors was constant across pollen load sizes, suggesting that, for this species, differential performance of pollen donors can occur at pollen load sizes that are likely to occur in field populations.  相似文献   

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Plants of red fescue (Festuca rubra), a commercially important turf grass, are infected by the fungal endophyte Epichloë festucae in semiarid natural grasslands, known as dehesas, in western Spain. We used amplified fragment length polymorphism (AFLP) markers to analyse the genetic polymorphism existing in two natural populations of Epichloë festucae. Linkage disequilibrium and the presence of clonal lineages indicated that nonrecombinant asexual reproduction predominates in both populations. However, most genetic variation detected was found to occur within populations, with only a moderate amount of genetic differentiation between populations (FST: 0.197). Overall, the study suggests that dehesa grasslands are useful reservoirs of Epichloë festucae endophytes, and provides information on population structure which is relevant to design sampling strategies.  相似文献   

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Olsson  P.A.  Francis  R.  Read  D.J.  Söderström  B. 《Plant and Soil》1998,201(1):9-16
Fatty acid analysis was used for determining the extent of the development of the external mycelium of AM fungi (mixed inoculum from a sand dune) growing from roots of Festuca rubra and Plantago lanceolata in calcareous dune sand. The plants were raised in chambers specially designed to permit the growth of AM mycelium in root-free compartments. In two separate experiments, growth of external mycelium in the root-free compartments was detected and the amount of mycelium was estimated using the indicator of AM fungal biomass, phospholipid fatty acid (PLFA) 16:15. The results showed that the PLFA 16:15 was suitable for estimating the mycelium emerging from the mixed inoculum obtained from the field roots of F. rubra and P. lanceolata.The PLFA 16:15 showed external mycelium to become established in the root-free compartments within a period of 3 weeks and the amount of mycelium to continue to increase at 6 and 9 weeks. Increases in neutral lipid fatty acid (NLFA) 16:15 (indicator of storage lipids) over time were inconsistent between the two experiments, but appeared to follow patterns of sporulation in each experiment.In both experiments, the root-free compartment was colonised by saprophytic fungi to a greater extent in the case of non-mycorrhizal than of AM treatment, as indicated by an increase in PLFA 18:26,9 (indicator of saprophytic fungi). The absence of an increase in the case of AM treatment indicates that AM fungal mycelium can negatively affect the growth of saprophytic fungi in this soil type. This result was, however, only weakly supported by measurements of ergosterol content. The analysis of bacteria specific PLFAs showed that bacterial biomass was not affected by the AM mycelium.  相似文献   

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