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1.
Population structure, fruit production and dispersal, and recruitment of Rhus integrifolia, a gynodioecious sclerophy llous shrub living in coastal chaparral, were studied in two localities in southern California last burned 60 and 90 years ago. Though hermaphroditic plants produce some fruits, only the male-sterile plants bore significant numbers. Among the sample plants, one individual accounted for 50% of the crop measured. Terrestrial animals, through the loss of some seeds taken for consumption, play a decisive role in the seed dispersal, promoting the establishment of seedlings outside the parent's canopy. Birds have not been demonstrated to contribute to long distance dispersal, but they are responsible for dropping 25% of the fruits collected below the R. integrifolia canopies, 36%) of which were completely destroyed. Allelopathic effects were not observed in laboratory assays, and germination is probably not influenced by the species beneath which seeds have been deposited. This pattern can explain the non-aggregated distribution of individuals observed in the studied populations. We conclude that establishment of new individuals has been continuous at both localities and that the populations of R. integrifolia are increasing in these long unburned stands. This may be indicative of a successional trend in unburned chaparral and coastal scrub toward a sclerophy llous woodland.  相似文献   

2.
Wang G  Jiang G  Yu S  Li Y  Liu H 《植物学报(英文版)》2008,50(5):522-530
Rhus typhina, an alien species introduced from North America, was identified as a main afforestation species in Beijing municipality. However, its invasiveness is still at odds. To clariflj this problem, we applied the North American Screening System and the Australian Screening System to preliminarily predict its invasion possibility. Both screening systems gave the same recommendation to "reject". The geographical distribution was surveyed, with the population features of R.typhina against the native plant communities being assessed. With anthropogenic assistance, R. typhina has been scattered on almost all habitats from downtown to mountains, including roadsides, farmlands and protected areas. As a clonal shrub,R. typhina possessed a high spreading rate, varying from 6.3 m13 years at sterile habitats to 6.7m/3 years at fertile ones.Significantly lower species richness, individual density and diversity were observed in the R. typhina community than those of the native Vitex negundo Linn.var. heterophylla (Franch.) Rehd. community at both sterile and fertile habitats. Continual wide plantation of R. typhina may further foster its population expansion, which helps the species to overcome spatial isolation. The fact that each root fragment can develop into a new individual makes R. typhina very difficult to be eradicated once established. From a biological point of view, we believe that R. typhina is a plant invader in Beijing. We therefore suggest the government should remove the name of R. typhina from the main tree species list in afforesting Beijing.  相似文献   

3.
David A. Young 《Brittonia》1974,26(3):241-255
Five populations ofRhus integrifolia andR. ovata were studied and, based upon morphological characteristics and pollen viability, a number of putative hybrids were found in those areas where the two species are sympatric. Diagnostic characteristics most useful for distinguishing the species and their hybrids are leaf morphology, sepal pubescence, petiole length, and petal size. Introgression was evident in at least three populations, which suggested that hybridization between the two species is an ancient phenomenon. Evolutionarily, hybridization between the two taxa has probably been of little consequence.  相似文献   

4.
Rhus michauxii, a rare plant species endemic to the southeastern United States, was previously known only from central North Carolina and one site in Georgia. An additional site, which is now believed to represent the largest known concentration of R. michauxii, was recently discovered at Ft. Pickett near Blackstone, Virginia. Morphological characteristics in several of the Ft. Pickett Rhus populations appear to be intermediate between R. michauxii and the widespread R. glabra, a closely related congener that co-occurs at Ft. Pickett. Although morphological evidence of hybridization between R. michauxii and R. glabra in North Carolina has been provided previously, genetic marker data are lacking. In the present study we examined levels of allozyme variation at 11 polymorphic loci within and among seven populations of R. michauxii, one population of R. glabra, and four putative hybrid populations at Ft. Pickett. Overall, R. michauxii had typical levels of within-population genetic variation when compared to other species with similar life-history characteristics. In contrast, the proportion of genetic variation among populations (G(ST)) was considerably lower than expected. Finally, R. michauxii and R. glabra appear to have a fixed allelic difference at the Idh2 locus. This enabled us to confirm hybridization in all four of the putative hybrid populations and one of the R. michauxii populations.  相似文献   

5.
The interaction between frugivorous birds and trees producing bird-dispersed seeds in devastated areas has been considered to be weak, owing to the paucity of avifauna and/or food resources for birds. Here, we present evidence that strong interactions between birds and plants may promote the enlargement of tree distribution on harsh environments. The summit of Mount Koma, northern Japan, was denuded by the 1929 volcanic eruption. Vegetation cover gradually decreases from the bottom (secondary forest) to the top (bareground) of the mountain. We recorded 48 bird species in the four seasons of 2001, along a 5-km line transect on the southwestern slope of the mountain. Birds faeces collected along the transect contained seeds of more than 14 plant taxa. Five of the 14 taxa were bird-dispersal tree species ( Rhus trichocarpa , Sorbus commixta , Prunus ssiori , Prunus maximowiczii and Prunus sargentii ) and were established in the summit area. Most faeces were derived from Corvus spp. (mostly C . macrorhynchos ) and Turdus naumanni . In particular, the seeds of R . trichocarpa were found mostly from the faeces of Corvus spp. and the seeds of Gaultheria miqueriana , a shrub species, were only from T . naumanni . Rhus trichocarpa retained fruits on the canopy at all times of the year, and crows could feed on them even when food resources were poor in winter. Rhus trichocarpa seedlings established well near rock at higher elevation, while they occurred mostly under the larch canopy of larches at lower elevation. Crows mostly utilized tree canopies and rocks as perches in respective habitats. Therefore, seedlings should be abundant in specific habitats at different elevations. Size-class distribution of seedlings suggested that seedling mortality was lower at higher elevation where open sites were more abundant. These findings indicate that strong mutual advantages for C . macrorhynchos and R . trichocarpa on denuded areas play an important role on revegetation.  相似文献   

6.
Morphology and physiology of fruit and seed development were compared in Rhus aromatica and R. glabra (Anacardiaceae), both of which produce drupes with water-impermeable endocarps. Phenology of flowering/fruiting of the two species at the study site was separated by ∼2 mo. However, they were similar in the timetable and pattern of fruit and seed development; it took ∼2 mo and ∼1.5 mo for flowers of Rhus aromatica and R. glabra, respectively, to develop into mature drupes. The single sigmoidal growth curve for increase in fruit size and in dry mass of these two species differs from the double-sigmoidal one described for typical commercial drupes such as peach and plum. Order of attainment of maximum size was fruit and endocarp (same time), seed coat, and embryo. By the time fruits turned red, the embryo had reached full size and become germinable; moisture content of seed plus endocarp had decreased to ∼40%. The endocarp was the last fruit component to reach physiological maturity, which coincided with development of its impermeability and a seed plus endocarp moisture content of <10%. At this time, ∼50, 37, and 13% of the dry mass of the drupe was allocated to the exocarp plus mesocarp unit, endocarp, and seed, respectively. The time course of fruit and seed development in these two species is much faster than that reported for other Anacardiaceae, including Rhus lancea, Protorhus, and Pistacia.  相似文献   

7.
Sequences of internal transcribed spacers (ITS) of nuclear ribosomal DNA, the chloroplast ndhF gene, and chloroplast trnL-F regions (trnL intron, and trnL [UAA] 3' exon-trnF [GAA] intergenic spacer) were used for phylogenetic analyses of Rhus, a genus disjunctly distributed in Asia, Europe, Hawaii, North America, and Northern Central America. Both ITS and cpDNA data sets support the monophyly of Rhus. The monophyly of subgenus Rhus was suggested by the combined cpDNA and ITS data, and largely supported in the cpDNA data except that Rhus microphylla of subgenus Lobadium was nested within it. The monophyly of subgenus Lobadium was strongly supported in the ITS data, whereas the cpDNA data revealed two main clades within the subgenus, which formed a trichotomy with the clade of subgenus Rhus plus R. microphylla. The ITS and cpDNA trees differ in the positions of Rhus michauxii, R. microphylla, and Rhus rubifolia, and hybridization may have caused this discordance. Fossil evidence indicates that Rhus dates back to the early Eocene. The penalized likelihood method was used to estimate divergence times, with fossils of Rhus subgenus Lobadium, Pistacia and Toxicodendron used for age constraints. Rhus diverged from its closest relative at 49.1+/-2.1 million years ago (Ma), the split of subgenus Lobadium and subgenus Rhus was at 38.1+/-3.0 Ma. Rhus most likely migrated from North America into Asia via the Bering Land Bridge during the Late Eocene (33.8+/-3.1 Ma). Rhus coriaria from southern Europe and western Asia diverged from its relatives in eastern Asia at 24.4+/-3.2 Ma. The Hawaiian Rhus sandwicensis diverged from the Asian Rhus chinensis at 13.5+/-3.0 Ma. Subgenus Lobadium was inferred to be of North American origin. Taxa of subgenus Lobadium then migrated southward to Central America. Furthermore, we herein make the following three nomenclatural combinations: (1) Searsia leptodictya (Diels) T. S. Yi, A. J. Miller and J. Wen, comb. nov., (2) Searsia pyroides (A. Rich.) T. S. Yi, A. J. Miller and J. Wen, comb. nov., and (3) Searsia undulata (Jacq.) T. S. Yi, A. J. Miller and J. Wen, because our analyses support the segregation of Searsia from Rhus.  相似文献   

8.
The reactions of Rhus vernicifera (monophenol,dihydroxyphenylalanine: oxygen oxidoreductase, EC 1.14.18.1) with the reducing substrates hydroquinone and ascorbic acid have been investigated with the stopped-flow technique. Rhus laccase appears to be present in two molecular forms with a pH-sensitive equilibrium constant regulating the relative concentrations of each species. A model for the reaction of Rhus laccase with reducing substrates has been formulated. The model is similar to one formulated earlier for the anaerobic reduction of laccase from Polyporus versicolor (Andréasson, L.-E., Malstr?m, B.G., Str?mberg, C. and V?nng?rd, T. (1973) Eur. J. Biochem. 34, 434-439) and accounts for the reduction also of this enzyme. The essentials of the model are as follows: Electrons are taken up from reductants one at a time. The type 1 Cu2+ has a central role in mediating the transfer of at least one of the electrons needed for the reduction of the co-operative two-electron acceptor. Intramolecular reactions determine the concentrations of two molecular forms of the enzyme and influence the rate of reduction of the two-electron acceptor. The model, which has been used for successful simulations of the anaerobic reduction of Rhus laccase, is capable of explaining the reduction of laccases also in the presence of the inhibitor F-. In addition, the model gives an explanation of the behaviour of the laccases when reducing substrates and O2 are simultaneously present and is consistent with earlier observations of the post-steady-state reduction of the type 1 Cu2+ and the two-electron accetor (Holwerda, R.A. and Gray, H.B. (1974) J. Am. Chem. Soc. 96, 6008-6022).  相似文献   

9.
Hybridization and introgression are common processes among numerous plant species that present both challenges and opportunities for studies of species delimitation, phylogenetics, taxonomy and adaptation. Rhus integrifolia and R. ovata are two ecologically important shrubs native to the southwestern USA and Mexico, and are known to hybridize frequently, but the morphological, genetic and ecological implications of hybridization in these species are poorly studied on a broad geographic scale. Analyses were conducted using leaf morphology, genetic variation of plastid and nuclear loci, and species distribution models for both species and their putative hybrid introgressants across 19 localities in California and Arizona, USA. These analyses revealed evidence for morphological and genetic distinction among localities comprising putative parental species, but a high degree of morpho-genetic intermediacy among localities with putative hybrids. Comparison of morphological and genetic population structure among localities revealed evidence for putative local adaptation or widespread phenotypic plasticity. Multiple regression models identified a weak but statistically significant negative association between leaf area and precipitation. Finally, species distribution modeling inferred northward range shifts over time, with both species predicted to occupy more coastal regions in the future, possibly increasing the frequency of hybridization among them. These findings underscore the importance of integrative assessment of multiple data sources in the study of hybridizing species and highlight the R. integrifolia-ovata complex as a powerful model for investigating the adaptive implications of hybridization.  相似文献   

10.
The response to freeze-thaw stress was examined for two co-occurring evergreen species, Malosma laurina and Rhus ovata. Laboratory and field experiments on adults and seedlings were made in the spring and winter in 1996 and again on adults in 2003 and 2004. Laboratory and field results indicated that the stem xylem for adults of M. laurina and R. ovata were similarly susceptible to freezing-induced cavitation (percentage loss of conductivity = 92 ± 2.6% for R. ovata and 90 ± 4.2% for M. laurina at ≤ -6°C). In contrast, leaves of M. laurina were more susceptible to freezing injury than leaves of R. ovata. Among seedlings in the field, leaves of M. laurina exhibited freezing injury at -4°C and total shoot mortality at -7.2°C, whereas co-occurring seedlings of R. ovata were uninjured. Surprisingly, R. ovata tolerates high levels of freezing-induced xylem embolism in the field, an apparently rare condition among evergreen plants. Rhus ovata avoids desiccation when xylem embolism is high by exhibiting low minimum leaf conductance compared to M. laurina. These results suggest a link between minimum leaf conductance and stem hydraulics as a mechanism permitting the persistence of an evergreen leaf habit in freezing environments.  相似文献   

11.
盐肤木是一种重要的经济树种,可为医药和工业染料提供原料。盐肤木具有较强的抗旱、耐寒、耐盐,可在温带、暖温带和亚热带地区生长。本研究首次对盐肤木叶绿体基因组进行从头测序(de novo sequencing)组装研究。结果表明,盐肤木叶绿体基因组长度为159082 bp,具有典型的四部分结构,两个单拷贝区被一对反向重复区分隔。LSC和SSC的长度分别为85394 bp和18663 bp。叶绿体基因组总共编码126个基因,其中包括88个蛋白编码基因,8个rRNA基因,30个tRNA基因。在叶绿体基因组中,61.97%的序列为基因编码区。在盐肤木叶绿体基因组中,只有8个基因含有内含子,除ycf3基因(2个内含子)外,其余均含有1个内含子。盐肤木叶绿体基因组总共存在755个SSR位点。SSR主要由二核苷酸和单核苷酸组成,分别占60%(453)和28.74%(217)。聚类分析结果表明,漆树科与盐肤木最为接近,其次为槭树科和无患子科。本研究为盐肤木的分类提供了分子基础。本研究是关于盐肤木叶绿体基因组的首次报道,对了解其光合作用、进化和叶绿体转基因工程具有重要意义。  相似文献   

12.
Rhus pygmaea , a new species endemic to amphibolitic serpentine soils near Barberton, Mpumalanga (Eastern Transvaal) is described and illustrated. It has affinities with R. pondoensis Schonl., but differs primarily in its dwarf habit, narrower leaflets, reduced inflorescence and male flowers having a conical pistillode.  相似文献   

13.
Leaf death due to freezing was examined for four, co-occurring species of chaparral shrubs from the Santa Monica Mountains of southern California, Rhus laurina (= Malosma laurina), R. ovata, Ceanothus megacarpus, and C. spinosus. Measurements were made on seedlings vs. adults for all species, and for Rhus spp. in winter vs. summer, and at a warm vs. a cold site. We used four methods to determine the temperature for 50% change in activity or cell death (LT(50)) of leaves: (1) electrical conductivity (electrolyte leakage into a bathing solution), (2) photosynthetic fluorescent capacity (Fv/Fm), (3) percentage of palisade mesophyll cells stained by fluorescein diacetate vital stain, and (4) visual score of leaf color (Munsell color chart). In all four species seedlings were found to be more sensitive to freezing temperatures than were adults by 1°-3°C. For adults the LT(50) ranged from -5°C for Rhus laurina in the summer to -16°C for Rhus ovata in the winter. The LT(50) of R. ovata located at a colder inland site was 4C lower than R. ovata at the warmer coastal site just 4 km apart, suggesting ecotypic differences between R. ovata at the two sites. Both R. laurina and R. ovata underwent significant winter hardening. At the cold site, R. ovata acclimated by 6°C on average, while R. laurina acclimated by only 3°C. These results were consistent with species distributions and with field observations of differential shoot dieback between these two congeneric species after a natural freeze-thaw event in the Santa Monica Mountains.  相似文献   

14.
火炬树抗螨性生物测定   总被引:1,自引:0,他引:1  
李中新  孙绪艮  李庆和  郭慧玲 《昆虫学报》2007,50(12):1309-1314
本文分别测定了二斑叶螨Tetranychus urticae Koch和山楂叶螨Tetranychus viennensis Zacher对火炬树的选择性,以及限制性条件下火炬树对叶螨的生存及产卵的影响。结果表明:在火炬树叶和苹果叶之间,二斑叶螨和山楂叶螨在2 h, 6 h, 10 h, 12 h对火炬树的选择率分别为9.5%, 6.5%,5%,5%和2%,5%,1%和0,显著低于对苹果的选择率。被限制于火炬树叶上生存的山楂叶螨144 h后死亡率100%,产卵力随生存时间增加而下降,至96 h后产卵终止; 被限制于火炬树叶上生存的二斑叶螨240 h后全部死亡,整个观察期内(24~216 h)始终没有产卵。据此认为: 叶螨强烈拒食火炬树,火炬树对叶螨具有生存、产卵抑制作用,但这种抑制作用呈现种间差异。  相似文献   

15.
The expansion of C(3) shrubs into C(4)-dominated tallgrass prairies represents a fundamental shift in growth-form dominance accompanied by changes in resource acquisition and use. We assessed these changes by comparing the ecophysiological traits of the dominant C(4) grass Andropogon gerardii, with traits of three C(3) invasive shrub species, Cornus drummondii, Prunus americana, and Rhus glabra. We tested the hypothesis that ecophysiological traits of the shrubs would be similar within this growth form but distinct from grasses and that these species would conform to the two-layer soil water model. Photosynthetic rates in R. glabra were similar to A. gerardii and higher than in the other two shrubs, while water use efficiency was markedly greater in A. gerardii. Among all species, midday xylem pressure potentials (XPP) were distinctly lower (70%) for P. americana, but were similar among the other species. Predawn XPP was related to soil water at shallow depths for A. gerardii (r(2) = 0.59) and P. americana (r(2) = 0.62), and to deeper soil moisture for R. glabra (r(2) = 0.63); there was no relationship for C. drummondii at any soil depth. Thus, a simple two-layer soil water model for partitioning shrub/grass resource acquisition was not appropriate for this grassland. We conclude that these shrubs could not be considered functional equivalents from an ecophysiological perspective, nor were they, as a group, distinct from A. gerardii in resource acquisition and use.  相似文献   

16.
侯玉平  柳林  初航  马淑杰  赵丹  梁荣荣 《生态学报》2015,35(16):5324-5330
生物入侵在世界范围内广泛发生,严重威胁当地生物多样性和生态系统稳定性。植物与土壤之间的相互作用在决定植物的竞争力以及分布格局中起着重要作用,是影响外来植物入侵力和生态系统可入侵性的一个重要方面。目前,有关研究已成为植被生态学与入侵生态学的研究热点。引自北美的外来植物火炬树(Rhus typhina L.)已成为我国北方主要的入侵木本植物之一。比较了火炬树单优林型、火炬树+刺槐(Robinia pseudoacacia L.)混交林、火炬树+麻栎(Quercus acutissima Carruth.)混交林、火炬树+银白杨(Populus alba L.)混交林4种不同林型的土壤微生物群落结构、土壤酶活性和土壤养分含量特征。结果表明:火炬树单优林土壤细菌、放线菌数量明显高于各混交林型,而真菌数量无显著差异;土壤酶活性方面,火炬树单优林脲酶、过氧化氢酶活性高,土壤磷酸酶活性低;火炬树的入侵显著提高了土壤全碳、全氮、全磷和硝态氮含量,同时明显降低了土壤铵态氮含量。硝态氮含量的增高可能与火炬树入侵造成土壤微生物群落组成变化、土壤硝化速率高有关;而火炬树入侵降低了土壤铵态氮含量,说明该物种可能更易于吸收利用铵态氮。以上研究结果表明,火炬树可以改变土壤生态系统的微生物群落组成和土壤酶活性并影响土壤相关营养元素循环,从而可能使其在与当地植物的竞争中获得优势,为自身的入侵创造有利条件。  相似文献   

17.
Journal of Plant Biochemistry and Biotechnology - The sumac species Rhus chinensis is widely used in traditional Chinese medicine. APX is the key enzyme in hydrogen peroxide degradation, and may...  相似文献   

18.
Summary Laurel Sumac (Rhus laurina) is a dominant member of the coastal chaparral community of southern California that survives periodic burning by wildfires by resprouting from a lignotuber (root crown). We investigated the physiological basis for resprouting by comparing shoot elongation, leaf nitrogen content, tissue water status, leaf conductance to water vapor diffusion, and photosynthetic rates of post-fire R. laurina to those of adjacent unburned shrubs. Resprouts had higher rates of shoot elongation, leaf conductance, and photosynthesis than mature, unburned shrubs. Leaf nitrogen contents were elevated in burned shrubs even though their leaves developed interveinal chlorosis. A comparison of soil water potential to predawn water potential indicated that roots of R. laurina remain active below 2 m during the first summer drought after wildfire. Our results support the hypothesis that lignotubers not only contain dormant buds that develop into aerial shoots after wildfire but they also supply nutrient resources that enhance shoot elongation. Because R. laurina is relatively sensitive to drought, yet very successful in its rapid recovery after fire, maintaining an active root system after shoot removal may be the primary function of the massive lignotuber formed by this species.  相似文献   

19.
Rhus coriaria L. (Anacardiaceae), sumac, is a common condiment, appetizer and souring agent in the Mediterranean region that has a long history in traditional medicine. R. coriaria has been prescribed for the treatment of many ailments including diarrhea, ulcer, hemorrhoids, hemorrhage, wound healing, hematemesis, and eye ailments like ophthalmia and conjunctivitis. The plant is also used as diuresis, antimicrobial, abortifacient and as a stomach tonic. Sumac is known to be rich in different classes of phytochemicals including tannins, polyphenols, flavonoids, organic acids and essential oils and continues to be a hot topic for extensive research work designed for revealing its phytochemical constituents and evaluating its bioactive properties. This review summarizes the recent phytochemical and diverse bioactivity studies on R. coriaria, especially those concerned with antitumor, antioxidant, hypoglycemic, antimicrobial, and anti‐inflammatory studies.  相似文献   

20.
五倍子蚜共6属12种, 除北美分布1属1种外, 其余分布东亚。本研究采用数值分类和分子系统发育分析方法对北美五倍子蚜Melaphis rhois的形态特点和分类地位进行研究, 以倍蚜6属8种179个有翅孤雌蚜为研究对象, 对其头部、胸部、腹部的直接测量特征48个、量度间比例特征31个及转化为数值的描述特征29个共108个特征进行分析。基于欧氏距离的聚类结果显示, 北美倍蚜M. rhois与倍蚜属关系较近, 五倍子蚜8个种共形成3个大的聚类簇, 北美倍蚜M. rhois与倍蚜属的倍蛋蚜Schlechtendalia peitan和角倍蚜S. chinensis聚为一支; 铁倍蚜属的肚倍蚜蛋铁亚种Kaburagia rhusicola ovogallis和肚倍蚜枣铁亚种K. rhusicola ensigallis与小铁枣蚜属的红小铁枣蚜Meitanaphis elongallis、圆角倍蚜属的倍花蚜Nurudea shiraii和红倍花蚜N. yanoiella与铁倍花蚜属的铁倍花蚜Floraphis meitanensis分别聚为一支。另外, 测定五倍子蚜8个种共16个样本的mtDNA COI基因序列(约1.2 kb), 最大简约法(maximum parsimony, MP)和最大似然法(maximum likelihood, ML)分子系统发育分析结果均显示北美倍蚜M. rhois与倍蚜属的关系密切, 和形态数据得到的结果一致; 但倍蚜8个种之间的聚类总体上与形态学研究结果不太一致, 铁倍花蚜属的铁倍花蚜和小铁枣蚜属的红小铁枣蚜、铁倍蚜属的肚倍蚜枣铁亚种和肚倍蚜蛋铁亚种与圆角倍蚜属的倍花蚜和红倍花蚜分别聚为一支, 彼此之间的关系尚需深入研究。  相似文献   

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