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1.
We examined germination and seedling survival of Petrocoptis grandiflora and Petrocoptis viscosa (Caryophyllaceae), two narrow endemic species from the northwest Iberian Peninsula. The experiments were carried out with seeds of three of eight populations of P. grandiflora and one of the three sole populations of P. viscosa. Under natural conditions, both P. grandiflora and P. viscosa produce very large numbers of seeds. However, the specific microhabitat of these species (cracks and crevices of limestone rockfaces) has very marked effects on seed germination, and subsequent seedling survival. In the present study, we examined the effects of light, cold treatment and seed weight on germination capacity. In the case of P. grandiflora, we also compared the germination of seeds of the different populations. In addition, we assessed seedling survival over a 1-year period. Seeds maintained in darkness showed higher germination percentages than seeds maintained with a 12:12 h photoperiod. The application of a short period of cold prior to germination had no significant effect in either species. In the case of P. grandiflora, population of origin had a significant effect on germination percentage. Of all the factors considered, seed weight was the most important source of variability, both in seed germination and subsequent seedling survival. In both species in the natural habitat, less than 10% of germinated seeds survived by the end of the year. Seedling survival was affected by microhabitat. Seedlings in non-rockface soil microhabitats were more likely to suffer herbivory or interspecific competition than seedlings in crevices in the rockface.  相似文献   

2.
The influence of soil pH, moisture, nutrient availability and indigenous microorganisms on the survival and growth of Bacillus thuringiensis and B. cereus spore inocula in soil was investigated. The factor of greatest importance was nutrient availability. B. thuringiensis could not grow under most natural soil conditions, whilst B. cereus grew only slowly. Supplementing soil with additional nutrients, or autoclaving, stimulated growth of the Bacillus populations. Growth was reduced by a low soil pH (5.2 compared to 7.3), whilst both Bacillus species grew faster and survived better in wetter (at 0, ?0.01 MPa) than drier (at ?0.10, ?1.00 MPa) soils.The death of B. thuringiensis in natural soil probably accounts for its rarity in the outdoor environment. It is suggested that this demise is attributable to a failure of B. thuringiensis to germinate in soil.  相似文献   

3.
Saponins occur in numerous plants, including agaves, determining benefic and harmful properties to humans; their presence may favor using plants as soap and other products, but also they may cause caustic effects producing contact dermatitis. In domestication, favorable and unfavorable properties of saponins may cause an increase or decrease of their content, respectively. This study quantified and identified saponins among wild and managed populations of three agave species: A. cupreata Trel. et Berger, A. inaequidens Koch with wild and cultivated populations used for mescal production, and A. hookeri Jacobi, existing exclusively cultivated, used for production of the fermented beverage pulque. We studied 272 plants from 19 populations, quantifying contents of crude saponins through spectrometry. In 12 populations, the saponins types were identified by High Performance Liquid Chromatography–Mass-Spectrography-Time-of-Flight HPLC-MS-TOF. The highest crude saponins content was recorded in A. hookeri (26.09 mg/g), followed by A. cupreata (19.85 and 15.17 mg/g in wild and cultivated populations, respectively). For A. inaequidens, we recorded 14.21, 12.95, and 10.48 mg/g in wild, silvicultural managed and cultivated populations, respectively. We identified 18 saponins types, A. inaequidens showing all of them. A hecogenin glycoside (HG1) is found in high amounts in A. hookeri but in low quantities in A. inaequidens and A. cupreata. A. inaequidens had the greatest diversity of saponins. The contents of crude saponins in A. inaequidens and A. cupreata decrease with management intensity, but contrarily to what we expected, it was the highest in A. hookeri. We hypothesize that such high amount could be due to some saponins, probably HG1, may be precursors of sugars.  相似文献   

4.
干旱胁迫对窄叶鲜卑花种子萌发及幼苗生长的影响   总被引：1，自引：1，他引：0  
[目的]研究干旱胁迫对窄叶鲜卑花种子萌发及幼苗生长的影响,为野生种驯化和种群恢复提供参考。[方法]以窄叶鲜卑花种子为实验材料,采用不同浓度聚乙二醇(PEG-6000)模拟干旱胁迫环境,研究干旱协迫强度对窄叶鲜卑花种子的吸胀速率、发芽率、发芽势、发芽指数、活力指数和种子抗旱萌发指数及幼苗生长情况的影响。[结果]随着干旱胁迫程度的加剧,窄叶鲜卑花种子的吸水过程表现出急速吸水期、缓慢上升期和吸水平稳期3个阶段;其发芽率、发芽势、发芽指数、活力指数和种子抗旱萌发指数及苗高、根长,苗重与胁迫强度均呈负相关;当PEG浓度达30%时,种子萌发完全被抑制。另一方面,种子群体萌动、萌发和出苗达50%所需时间随胁迫强度的增加而越发延迟,且各阶段对环境临界水势要求不同,出苗阶段最为严格,表明种子出苗过程对环境水分胁迫较为敏感,耐旱能力较弱。[结论]干旱胁迫显著抑制了窄叶鲜卑花种子的萌发和幼苗生长,也说明水分是窄叶鲜卑花种子萌发和幼苗形成的主导因素之一,在较干旱地区种植需要考虑水分的供给。  相似文献   

5.
People of the Tehuacán Valley, Central Mexico utilise the columnar cactus Escontria chiotilla for their edible fruits, gathering them in the wild and in silviculturally managed populations. Silvicultural management consists in sparing and enhancing selectively, in disturbed areas, individual trees producing fruits of the better quality for consumption and commercialisation. Fruits of trees in silviculturally managed populations are generally larger (27.23 ± 0.39 cm) and heavier (11.10 ± 0.44 g), with a higher amount of pulp (4.84 ± 0.27 g), and more (532.72 ± 15.60) and heavier (0.78 ± 0.013 mg) seeds than in wild non-manipulated populations (22.62 ± 0.31 cm, 6.44 ± 0.22 g, 2.33 ± 0.11 g, 407.63 ± 20.67, and 0.62 ± 0.015 mg, respectively). Phenotypes of trees producing better fruits were significantly more abundant in manipulated populations than in the non-manipulated ones. Artificial selection appears to be the cause of such differences among populations and, therefore, domestication process of this plant species is seemingly occurring under silvicultural management.  相似文献   

6.
For taxonomic purposes and because many wild relatives of Allium crops are endangered in their native habitat (Sancir et al., 1989), a collection of Allium species was built up in the IPK at Gatersleben. At present it consists of more than 3000 accessions representing about 330 species. In this context it was necessary to study the seed germination behaviour and dormancy of certain wild Allium species. Therefore, seeds of 91 wild and three cultivated Allium species were tested at germination temperatures of 5°, 11°, 16° and 26°C. The purpose of this study was to develop routine germination tests for the genebank work with wild alliums.  相似文献   

7.
Flowering phenology, soil seedbank and the impact of fire, weeds and grazing were investigated in two rare Acacia taxa restricted to the agricultural district north of Perth Western Australia. Acacia aprica is known from six extant populations and one extinct population. Five of the extant populations are restricted to linear road reserves with the sixth population located in a small native vegetation remnant. Acacia cochlocarpa ssp. cochlocarpa is known from a single population also situated on a road verge. Size class structure, levels of canopy death and an absence of juveniles indicated that all populations are in decline. Flowering intensity and success varied between populations and years in A. aprica and between years in A. cochlocarpa ssp. cochlocarpa. Seed bank analysis indicated that seeds were patchily distributed while experimental fires demonstrated that such events could break seed dormancy and promote germination. Both taxa have similar germination physiologies and showed increased germination after seeds were exposed to heat. Following emergence, however, competition with annual weeds had a negative impact on seedling growth and survival in both taxa. While vertebrate grazing had some influence, weeds were the major inhibitory influence on recruitment. Reduced fire frequencies since fragmentation may be responsible for population decline in both taxa but other site specific factors such as weeds and grazing may affect the establishment of seedlings following fire.  相似文献   

8.
《Biological conservation》2002,108(2):213-219
Management of dehesas (i.e. oak woodland pastures) creates a patchwork of sectors that differ in their structure and composition of understorey vegetation. We analysed whether different management techniques affect the populations of several species of lizards (Podarcis hispanica, Psammodromus algirus, Psammodromus hispanicus, Acanthodactylus erythrurus, and Lacerta lepida). Multivariate analyses showed that lizards preferentially used forested areas with scrub while they avoided open herbaceous areas. The abundance of lizards increased when the understorey bushy vegetation increased. In contrast, grasslands or cereal fields were scarcely occupied even if holm oak trees (Quercus ilex) were present, apparently because low shrubs were scarce here. Therefore, some of the traditional management practices of dehesas may negatively affect lizard populations. These conclusions could have wider implications for the design of wildlife reserves within dehesas, which has been previously based on the umbrella species concept (e.g. some dehesas are managed for imperial eagle Aquila adalberti conservation), without considering habitat requirements of other representative animal groups.  相似文献   

9.
Escontria chiotilla is a columnar cactus that grows in the arid and semiarid lands of Central Mexico and produces edible fruit with economic. In the wild, this plant species is distributed as part of thorn-scrub and tropical deciduous forests, but in the Tehuacán Valley also occurs in silvicultural managed in situ populations, in which people practise artificial selection enhancing phenotypes with larger fruits. The population genetics of wild and managed populations was studied to analyse the effects of management on genetic structure of E. chiotilla. A total of 150 individuals from six populations were studied, analysing 13 loci for eight enzymes by starch gel electrophoresis. The genetic variation in wild populations was significantly higher than in managed populations (Ho = 0.079, He = 0.134, HT = 0.370, and Ho = 0.052, He = 0.110, HT = 0.298, respectively), indicating that silvicultural management has caused a reduction of the genetic variation in populations. Most of the genetic variation in both wild and managed populations occurs within populations (DST = 0.027 in the wild and 0.018 in managed populations). The genetic distance coefficients were slightly different for silvicultural managed populations than in wild ones, illustrating an incipient effect of management on the genetic structure of populations. However, values of NmGST = 3.845 and NmFST = 3.848 indicate that a high gene flow counteracts the effects of human selection on the differentiation of populations.  相似文献   

10.
As a part of a wide project to determine the conservation status and collecting expeditions of wild plant genetic resources of genus Brassica (species n = 9) of the Iberian Peninsula, twenty-nine wild populations of Brassica oleracea L. were characterised using the isoenzymatic profiles of seeds collected from their natural habitats. The zymograms, obtained using bulking seeds, identified samples faster than other methodologies, which could be useful in seed bank management as well as the regular monitoring of the status of in situ conservation. Five isoenzymatic systems were analysed considering the electrophoretic phenotype of the whole population (not individuals). Using enzymatic bands as qualitative characters, data were evaluated using phenetic clustering methods unweighted pair group method using arithmetic averages. The enzyme systems showed high polymorphism levels, and each studied population of B. oleracea showed a characteristic zymogram in each of the assayed enzyme systems. The clustering analysis using the Dice coefficient showed that most of the studied populations can be considered significantly different from each other. This study proposes a rapid screening strategy for obtaining the electrophoretic profiles of samples and comparing population patterns. Two main of conclusions can be drawn from the results of this work: (1) compared to other molecular techniques and the efficiency and reliability of isoenzyme analyses, this method appears to be a useful tool for a rapid characterisation of samples; (2) in situ observations of populations suggest that conservation status of wild B. oleracea in their natural habitat in Spain can be considered satisfactory.  相似文献   

11.
为探究2-(3,4-二氯苯氧基)乙基二乙胺(2-(3,4-dichlorophenoxy) ethyl triethylamine,DCPTA)在干旱胁迫下对玉米种子萌发的影响,使用聚乙二醇(polyethylene glycol-6 000,PEG-6 000)和浓度为0.5、1.0、1.5 mg/L的DCPTA混合溶液对玉米种子进行浸泡处理,采用种子标准发芽试验总结得出不同浓度的DCPTA对玉米种子发芽情况影响的规律,再结合低场核磁共振(low field nuclear magnetic resonance,LF-NMR)及核磁共振成像(magnetic resonance imaging,MRI)技术,通过研究其内部水分变化情况、水分迁移规律及水分分布特征解释造成该结果的原因。试验结果表明:一定浓度的DCPTA可以提高玉米种子萌发过程中的耐旱性能,加快种子内部水分的存储速率,提供种子萌发所需的水分条件,减轻干旱胁迫对玉米种子造成的损害。DCPTA对玉米种子干旱胁迫的缓解效果随着其浓度的升高呈现先上升后下降的趋势,以1.0 mg/L的DCPTA处理效果最显著(P<0.05)...  相似文献   

12.
Calcareous grasslands are among the most diverse habitats, supporting species-rich vegetation. Propagule limitation and availability of microsites for germination represent major constraints to the successful restoration of these grasslands. To date, little information is available on the effectiveness of seed addition and soil disturbance on the restoration success of encroached semi-natural calcareous grasslands. Here, we conducted a 1 year before – 9 year after control-impact (BACI) study aimed at testing the effect of the addition of seeds of native species and livestock grazing on calcareous grasslands. Each restoration measure and their combination differed in their impact on these communities and varied over time. Grazing had a significant, beneficial, impact on these communities, although the impact was species-specific. On average, grazed plots were characterized by a higher number of species and a lower vegetation cover. Nine years after treatment application, grazed site were dominated by Trifolium incarnatum subsp. molinerii, Xeranthemum cylindraceum, Orlaya grandiflora, Teucrium chamaedrys and Bromus erectus while ungrazed sites were dominated by B. erectus, X. cylindraceum, O. grandiflora and Prunus spinosa. Only 8 out of 34 species responded significantly to disturbance or/and disturbance and seed addition while 22 species were significantly affected by the sampling year and 18 by a blocking factor. The low recruitment from added seeds and the fact that seed addition is a time-and labor-consuming activity suggests that an adequate level of disturbance and natural regeneration represent the most cost-effective approach to the restoration of these calcareous grasslands.  相似文献   

13.
Glycyrrhiza uralensis Fisch. ex DC. (Chinese licorice) is an important medicinal plant in Mongolia. Despite its traditional role in local healing systems, little is known about the existing intra-specific diversity of this species. The aim of the present study therefore was to analyze morphological and genetic diversities of G. uralensis in the Bulgan River Basin in Western Mongolia and to test different treatments aimed at breaking seed dormancy in order to facilitate effective cultivation of this species. Morphological measurements were taken and leaf and seed samples were collected in eight populations of the Bulgan River Basin. Subsequently, DNA was extracted from leaves and analyzed employing amplified fragment length polymorphisms. A total of 11 treatments were used to test and enhance seed germination. Morphological characteristics differed among populations. Treatments used in the study affected total emergence and mean days to germination of the seeds differently, but populations did not differ in their response whereas differentiation within populations was high. Mechanical and acid scarifications were more effective compared to other treatments. The level of genetic diversity in the studied populations was lower than the average value of the short-lived perennial herbs, but close to that of the self-breeding species. Most of the genetic variation was within populations. Chinese licorice is suitable for cultivation in the Bulgan River Basin and effective scarification can increase germination of seeds across the populations collected in our study area.  相似文献   

14.
Brachycome muelleri Sonder (Corunna daisy) is an endangered annual herb, endemic to the upper Eyre Peninsula of South Australia. It is restricted to a single population occupying an area of approximately 3 ha on steep, south-facing cliff-foot slopes of the Baxter Hills. Its unique habitat, within an otherwise generally arid region, optimises soil moisture retention through the provision of concentrated water catchment, shade, and low evaporation rates during the growing season. Weeds had the potential to significantly disrupt recruitment, growth and reproductive output, but grazing did not constitute a direct threat to the population. Fresh seeds were innately dormant, requiring a period of after-ripening before they would germinate. Dormancy was artificially broken by gibberellic acid (GA3) treatment. Germination was optimal at 20 °C, and it was proposed that temperature plays an important role in regulating germination in situ. B. muelleri seeds did not respond to smoked water treatment, and GA3 (1000 mg l−1) was recommended as a routine seed treatment to stimulate germination. Trial translocations using seed as founder propagules resulted in low establishment, growth and flowering rates. Established seedlings provided several advantages over seed as founder propagules, including higher success rates, more vigorous growth, and improved seed yields in the first season. Successful regeneration, proliferation and expansion of a new translocated population was observed and recorded over four consecutive years. We suggest that conservation management of this species should include the establishment of several new populations by translocation to suitable, isolated, weed-free sites.  相似文献   

15.
The maintenance of wild populations of Greater Rhea (Rhea americana) through effective management requires an understanding of their habitat requirements in terms of vegetation composition and field configuration. We studied the relative influence of some anthropogenic variables (presence of route, house and fences) and resource variables (presence of water source, composition and coverage of plant species, vegetation height and bare soil), on the habitat use by a population of rheas in a cattle ranch of Buenos Aires Province, Argentina. Habitat use was determined indirectly by documenting the number of faeces in summer, autumn-winter and spring 1999. The presence or absence of faeces was related to the measured variables through discriminant analysis that allowed the elaboration of predictive models of habitat use by this species. Contrary to what was expected, those variables related to human activity showed a low predictive value on the habitat use by rheas when compared with resource variables. Rheas preferentially selected the stream area in all seasons and sites with great percent cover of Bupleurum sp., Phyla canescens, Sida leprosa, Plantago lanceolata, Trifolium repens, Lolium multiflorum, Stipa spp., and Stenotaphrum secundatum. Low vegetation height was another important component of rhea's habitat in summer and autumn-winter. The high accuracy level obtained by validation tests of this model supports its utility for the management of rhea populations in other cattle ranches of the region, and to analyze the suitability of other ranches for reintroduction programs.  相似文献   

16.
盐碱复合胁迫对水稻种子发芽的影响   总被引：1，自引：0，他引：1  
为研究盐胁迫与碱胁迫复合对水稻种子发芽的影响,采用模拟试验方法,将两种中性盐(NaCl、Na_2SO_4)和两种碱性盐(NaHCO_3、Na_2CO_3)按照不同比例[NaCl︰Na_2SO_4︰NaH∶CO_3︰Na_2CO_3分别为1︰1︰0︰0(A), 1︰2︰1︰0(B), 1︰9︰1︰0(C), 1︰1︰1︰1(D),9︰1︰1︰9(E)]混合,每个混合比例设不同总盐浓度(50 mmol·L~(-1)、100 mmol·L~(-1)、150 mmol·L~(-1)、200 mmol·L~(-1)),模拟20种盐碱胁迫环境,以去离子水作为对照(CK),研究不同盐碱混合胁迫对水稻种子发芽的影响。结果表明,水稻种子经两种中性盐混合胁迫溶液培养后,与CK相比,发芽率、发芽势、发芽指数的降幅分别为9.2%～74.4%、10.0%～48.9%、5.6%～55.6%,平均发芽时间延长3.2%～96.4%;随胁迫溶液中碱性盐比例的增加,与CK相比, B-E组发芽率分别降低8.9%～96.5%、15.0%～98.0%、7.5%～98.7%、18.9%～95.7%,发芽势分别降低20.0%～94.4%、13.2%～97.8%、3.3%～100%、36.7%～94.4%,发芽指数分别降低16.7%～94.4%、22.2%～100%、16.7%～100%、27.8%～94.4%,平均发芽时间较CK延长0.8～4.5倍,说明中性盐和碱性盐的混合胁迫溶液对水稻种子发芽的抑制作用更强。将在盐碱胁迫溶液中未萌发的水稻种子转移至蒸馏水中培养7d后,水稻种子的最终萌发率均达73.33%以上,表明胁迫溶液没有破坏水稻种子的活性,只是暂时性抑制了种子的萌发。试验结果表明:与单施中性盐比较,中性盐与碱性盐混合胁迫作用对水稻种子萌发的抑制作用更明显,且在中性盐与碱性盐混合溶液浓度达200mmol×L~(-1)时,种子发芽率接近0。  相似文献   

17.
Use and management of wild and weedy species may involve artificial selection, which can determine morphological, physiological, reproductive, and genetic divergences between wild and managed populations, resulting in the initial or incipient phases of plant domestication. In this study we combined ethnobotanical, morphological, phytochemical and genetic information for analyzing differences between managed and unmanaged populations of the Mexican edible weed, Epazote (Chenopodium ambrosioides L.), in Santa María Tecomavaca, Oaxaca, a rural community within the Tehuacán-Cuicatlán Biosphere Reserve, Mexico. Our hypothesis was that differences in morphology (e.g. leave dimensions and density of pubescence), phytochemistry (e.g. flavor, odor, and amount of strong scented and toxic compounds) and/or molecular genetic markers, between managed and wild populations of Epazote in Santa María Tecomavaca, would indicate that managed populations have been and/or are under a process of incipient domestication. Our results revealed the existence in the study area of morphological variants associated with a gradient of management intensity, which involved apparent improved palatability correlated with a lowering of chemical defense. Most remarkably, we found agreement in the groupings defined by the cluster analyses of morphological and genetic data. Although Epazote is considered a weed or, at best, a minor crop, the results from four lines of evidence (cultural differentiation patterns, gigantism, reduction in chemical defenses, toxic compounds and inheritance of adaptive traits) suggest the existence of an incipient domestication process in the study zone.  相似文献   

18.
Collection of plants and seeds from wild populations threatens a large number of cycad species. We investigated to what extent individual life history stages contribute to population growth (λ) and compared two species with major differences in life histories in the African genus Encephalartos: Encephalartos cycadifolius, a highly persistent grassland species that resprouts after fire, and Encephalartos villosus, a relatively fast growing, non-sprouting forest species. Several harvesting scenarios impacting different sized individuals were simulated to determine the sensitivity of the two functional types to harvesting. In both species λ was most sensitive to changes in abundance of adult plants. The harvesting of seeds had minimal impact on population growth rates, whereas harvesting of adult plants led to rapid population decline. This response from two very different functional types suggests that the conservation of adult plants is critical for all cycad species. Despite similar responses to adult mortality, the two species had substantially different population growth rates. This determined recovery time after harvesting of adult individuals. Encephalartos cycadifolius is typical of highly persistent plant species associated with low levels of recruitment and unable to recover from even small losses of adults within a reasonable conservation time frame (<100 years). Our results suggest that the ability to recover from loss of individuals is an important factor that should be considered when assessing the vulnerability of wild populations to threats.  相似文献   

19.
Plantago cordata, the heart-leaved plantain, is a species of woodland streams that was formerly widespread in the eastern United States, but is now restricted to a few widely scattered localities. Visits to previously sampled sites confirmed that the species is on the decline. Detailed studies were made of populations on one stream system in North Carolina. Demographic studies of an originally vigorous population on a gravel bar showed that the population declined in numbers, average plant size, and reproductive output. The overall population along the whole stream system showed much less change, suggesting frequent localised shifts in population number. Morphological measurements on plants grown from seed under standard conditions showed genetic differentiation between populations within the stream system, as well as extensive genetic variation within populations. Measurements of reproductive effort on field-collected and herbarium specimens showed that P. cordata had the fewest seeds per unit leaf area of any Plantago species studied. A high rate of habitat destruction, subsequent high adult mortality but low reproductive output, low dormancy and low dispersal capacity between stream systems appeared to be the major reasons for the decline of the species. The requirement of the species for large leaves to intercept light, and extensive roots for anchorage, places limits on evolutionary shifts towards greater reproductive effort. Changes in the dispersal mechanism would entail a major evolutionary reorganisation of the present specialised water dispersal mechanism based on two seeds joined by a spongy placenta. It is emphasised that there is no a priori reason why evolutionary shifts should be more rapid in declining than in stable or increasing populations. Unlike the many weedy species in the genus, P. cordata appears to have been adapted to long-standing, stable stream environments of climax hardwood forests, and in spite of considerable physiological flexibility, has a life cycle that is not preadapted to shifting, highly unstable, man-made environments.  相似文献   

20.
The efficient storage and germination of seeds underpin the effective use of plants for livelihoods and sustainable development. A total of 204 wild species useful for local communities of the Tehuacán–Cuicatlán Valley were collected and stored in seed banks in country for long term conservation, and 66 % (i.e., 134) duplicated in the U.K., as an effective means of ex situ conservation. Of the 204 species, 147 (122 of which also duplicated in the U.K.) were previously listed as useful plants in the ethnofloristic inventory of the Valley. Based on literature surveys, we found that one of the major impediments to the use of stored seeds of wild species is the lack of knowledge of how to germinate the seed. In detailed studies, we found that seeds of 18 useful plant species from 10 different families germinated readily and could be propagated. In contrast, four species (Actinocheita filicina, Bursera submoniliformis, Karwinskia mollis and Lippia graveolens) produced dormant seeds and therefore further studies are needed before their use can be maximised in large scale propagation programmes in support of conservation and livelihoods. Overall, this large-scale study on useful wild plant species in Mexico confirms that conventional seed banking can effectively support sustainable development and livelihood programmes.  相似文献   

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