汕头3种人工红树林湿地大型底栖动物群落的比较

对广东省汕头市莲阳河口区恢复背景相同的拉关木(Laguncularia racemosa)、无瓣海桑(Sonneratia apetala)、海桑(Sonneratia caseolaris)3种人工林和光滩湿地中大型底栖动物群落进行比较研究。结果显示,4种生境中大型底栖动物优势种(Y>0.02)存在差异;相似性分析检验(One-Way ANOSIM)表明4种生境间大型底栖动物群落结构差异显著。等级聚类和非参数多变量标序也显示4种生境间的大型底栖动物群落结构差异显著。3种人工林中,无瓣海桑、海桑人工林中大型底栖动物群落结构较为相似;3种人工林中大型底栖动物物种多样性和生物量从大到小的排列次序为:拉关木>海桑>无瓣海桑。BIOENV分析表明大型底栖动物分布与林地土壤p H、有机质、砂粒和粉粒含量、红树植物平均株高、平均胸径、平均基径和冠幅(南北×东西)这些理化因子显著相关,这进一步证实了红树植物种类对林地大型底栖动物多样性和分布的影响。

外来红树植物拉关木入侵性研究

针对红树林湿地管理者和研究者中存在的对中国引入的外来红树植物拉关木(Laguncularia racemosa C.F.Gaertn.)是否具有入侵性的矛盾看法,对海南岛分布的拉关木进行了初步调查,并综述了已有的相关研究文献。拉关木在海南岛和华南地区的海岸湿地上生长良好,其植株生长旺盛,繁殖力强,并已自然扩散侵入海南乡土红树植物群落,具有潜在的生物入侵风险。提出对拉关木的潜在入侵性深入研究的几个重点问题,分别为拉关木与海南乡土红树植物的种间竞争机制,拉关木对乡土红树植物群落及其演替趋势的影响;拉关木繁殖体的自然扩散机制;拉关木种群遗传分化与环境适应机制,以期增进对拉关木潜在入侵性及其对海南乡土红树植物多样性潜在威胁的认识。

Hepatoprotective and antioxidant activity of a mangrove plant Lumnitzera racemosa

Objective:To identify the hepatoprotective and in vitro antioxidant activity of Lumnitzera racemosa(L.racemosa) leaf extract.Methods:Animals in Group 1 served as vehicle control. Group 2 served as hepatotoxin(CCL_4 treated) group.Group 3 served as positive control(Silyntarin) group,and Group 4.S and ft served as(73,150 and 300 nig/kg bw p.o.)L.racemosa leaf extract treated groups.Moreover,in vitro antioxidant DPPH,hydroxyl radical scavenging activity(HRSA),NO,ferric reducing antioxidant power(FRAP),lipid hydroperoxide(LPO) and super oxide dismutase(SOD) were also analyzed for the leaf extract.Results:The levels of the serum parameters such as serum glutamic oxaloacetic transaminase(SGOT).serum glutamic pyruvic transaminase(SGPT).alkaline phosphatase(ALP),bilirubin,cholesterol(CHL).sugar and lactate dehydrogenase(LDH) were significantly increased in COL_4 treated rats when compared with the control group(P<0.05).But the L.racemosa leaf extract treated rats showed maximum reduction of SGOT[(210.16±19.63)IU/L].SGPT[(82.37±13.87) IU/L].ALP[(197.63±23.4.3)IU/L],bilurubilt[(2.13 ±0.84) mg/dL].cholesterol[(163.83± 13.63) mg/dL].sugar[(93.00±7.63) mg/dL]and LDH[(1134.00) ±285.00)IU/L]were observed with the high dose(300 mg/kg bw) of leaf extract treated rats. Histopathological scores showed that,no visible changes were observed with high dose(300 mg/ kgbw) of leaf extract treated rats except few mild necrosis.The IC_(50) values were observed as(56.37 ±4.87)μg/mL,(57.68±1.98) μg/mL,(64.15±2.90)μg/mL,(61.94±3.98)μg/mL,(94.53± 1.68) μg/mL and(69.7±2.65)μg/mL for DPPH,HRSA,NO,FRAP,LPO and SOL) radical scavenging activities, respectively.Conclusions:In conclusion,the hepatoprotective effect of the L.racemosa leaf extract might be due to the presence of phenolic groups,terpenoids and alkaloids and in vitro antioxidant properties.

Larvicidal activity of green synthesized silver nanoparticles using bark aqueous extract of Ficus racemosa against Culex quinquefasciatus and Culex gelidus

Objective:To investigate the larvicidal activity of synthesized silver nanoparticles（Ag NPs） utilizing aqueous bark extract of Ficus racemosa（F.racemosa） was tested against fourth instar larvae of filariasis vector,Culex quinquefasciatus（Cx.quinquefasciatus） and japanese encephalitis vectors,Culex gelidus（Cx.gelidus）.Methods:The synthesized Ag NPs was characterized by UV-vis spectrum,X-ray diffraction（XRD）,Scanning electron microscopy（SEM） and Fourier transform infrared（FTIR）.The larvicidal activities were assessed for 24 h against the larvae of Cx.quinquefasciatus and Cx.gelidus with varying concentrations of aqueous bark extract off.racemosa and synthesized Ag NPs.LC50 and r2 values were calculated.Results:The maximum efficacy was observed in crude aqueous extract of F.racemosa against the larvae of Cx.quinquefasciatus and Cx.gelidus(LC50=67.72 and 63.70 mg/L;r2=0.995 and 0.985) and the synthesized Ag NPs(LC50=12.00 and 11.21 mg/L;r2=0.997 and 0.990).respectively.Synthesized Ag NPs showed the XRD peaks at 2θvalues of 27.61,29.60,35.48,43.48 and 79.68 were identified as （210）,（121）,（220）,（200） and（311） reflections,respectively.The FTIR spectra of Ag NPs exhibited prominent peaks at 3 425,2 878,1 627 and 1 382 in the region 500-3 000 cm-1.The peaks correspond to the presence of a stretching vibration of（NH） C=O group.SEM analysis showed shape in cylindrical,uniform and rod with the average size of 250.60 nm.Conclusions:The biosynthesis of silver nanoparticles using bark aqueous extract of F.racemosa and its larvicidal activity against the larvae of disease spreading vectors.The maximum larvicidal efficacy was observed in the synthesized Ag NPs.

Effects of variations in culture media and hormonal treatments upon callus induction potential in endosperm explant of Barringtonia racemosa L.

Objective: To induce callus from the medicinally valuable species, Barringtonia racemosa L.(B. racemosa) whereby the formation of callus is essential for micropropagation studies and in vitro plant secondary metabolites production.Methods: The callus induction potential in B. racemosa was assessed from endosperm explant cultured on different culture media and plant hormonal treatments. Lloyd and Mc Cown's woody plant medium and Murashige and Skoog's medium were used in the study as culture media. On the other hand, various concentrations and combinations of2,4-dichlorophenoxyacetic acid(1.0–2.0 mg/L) and kinetin(0.5–2.5 mg/L) had been incorporated in the culture media to exert the effects of auxin and cytokinin on callus induction.Results: From the present study, it was found that the profuse [(1.681 ± 0.770) g fresh weight,(0.239 ± 0.239) g dry weight] and friable callus formation was optimally produced with desirable morphology and considerable percentage of callus induction(56.70%) in endosperm explants cultured on 1.0 mg/L 2,4-dichlorophenoxyacetic acid and 1.5 mg/L kinetin in Murashige and Skoog's medium.Conclusions: A reliable protocol for inducing callus formation of profuse and friable morphology in endosperm explant of B. racemosa had therefore been successfully established.

Estimation of the carbon pool in soil and above-ground biomass within mangrove forests in Southeast Mexico using allometric equations

We report the results of carbon stored in soil and aboveground biomass from the most important area of mangroves in Mexico, with dominant vegetation of Red mangrove （Rhizophora mangle L.）, Black mangrove （Avicennia germinans L.）, white mangrove （Laguncularia racemosa Gaertn.） and button mangrove （Conocarpus erectus L.）. We sampled soils with high fertility during the dry season in 2009 and 2010 at three sites on Atasta Peninsula, Campeche. We used allometric equations to estimate above ground biomass （AGB） of trees. AGB was higher in C. erectus （253.18±32.17 t？ha-1）, lower in A. germinans （161.93±12.63 t？ha-1）, and intermediate in R. mangle （181.70±16.58 t？ha-1） and L. racemosa （206.07±19.12 t？ha-1）. Of the three studied sites, the highest absolute value for AGB was 279.72 t？ha-1 in button mangrove forest at any single site. Carbon stored in soil at the three sites ranged from 36.80±10.27 to 235.77±66.11 t？ha-1. The Tukey test （p 〈0.05） made for AGB was higher for black mangrove showed significant differences in soil carbon content between black mangrove and button mangrove. C. erectus had higher AGB compared with the other species. A. germinans trees had lower AGB because they grew in hypersaline environments, which reduced their development. C. erectus grew on higher ground where soils were richer in nutrients. AGB tended to be low in areas near the sea and increased with distance from the coast. A. germinans usually grew on recently deposited sediments. We assumed that all sites have the same potential to store carbon in soil, and then we found that there were no significant differences in carbon content between the three samples sites： all sites had potential to store carbon for long periods. Carbon storage at the three sampling sites in the state of Campeche, Mexico, was higher than that reported for other locations.

Two New Acetyl Cimicifugosides from the Rhizomes of Cimicifuga Racemosa

Two new acetyl cimicifugosides were isolated from the rhizomes of Cimicifuga racemosa. Their structures were elucidated as 2＇-O-acetyl cimicifugoside H-1 1 and 3＇-O-acetyl cimicifugoside H-1 2 by the spectroscopic evidence and chemical methods.

Corrosion Inhibition of Mild Steel in Hydrochloric Acid by Tannins Rom Rhizophora Racemosa

Studies on the corrosion behaviour of mild steel electrodes in inhibited hydrochloric acid are described. Conventional weight loss measurements show that a maximum concentration of 140 ppm of tannin from Rhizophora racemosa is required to achieve 72% corrosion inhibition. Similar concentration of tannin: H3PO4 in ratio 1:1 gave 61% inhibition efficiency, whereas efficiency obtained for phosphoric acid as inhibitor in the same environment was 55%. Corrosion rates obtained over six hours of exposure in 1M HCl solution at inhibitor concentrations of 140 ppm are 2 mA/cm2, 2.4 mA/cm2, 2.6 mA/cm2 and 6 mA/cm2 for tannin, tannin/H3PO4 and H3PO4-inhibited and uninhibited specimens respectively. Natural atmospheric exposure studies revealed that specimens treated in H3PO4 resisted corrosion for three weeks, while tannin treated specimens suffered corrosion attack after one week of exposure tests.

Enhancement of wound healing with roots of Ficus racemosa L.in albino rats

Objective:To establish the wound healing activity of aqueous and ethanolic extract of roots of Ficus racemosa(F.racemosa).Methods:Two models were performed to evaluate the wound healing activity Le.incision and excision models.In incision model the purameler which was carried out was breaking strength of wounded skin.In excision model percentage wound contraction and period of epithelialization were established for both the extracts.Reference standard drug was povidone iodine ointment for comparison with other groups.Results:From the observation in both two models,aqueous extract of F.racemosa was found to have greater wound healing activity in terms of breaking strength in incision model and percentage wound contraction,period of epithelialization in excision model than that of other groups.Conclusions: In conclusion,our findings suggest that aqueous extract of F.racemosa possesses better wound healing ability than the ethanolic extract.

Antioxidant and antibacterial activities and identification of bioactive compounds of various extracts of Caulerpa racemosa from Algerian coast

Objective:To evaluate the antibacterial and antioxidant activities and to identify the volatile bioactive compounds present in different crude extracts of the seaweed Caulerpa racemosa var.cylindracea.Methods:Caulerpa racemosa harvested from the intertidal zone of Mostaganem coast(N 35?54’37.94",E 0?3’17.37")was subjected to Soxhlet extraction using methanol,chloroform,and hexane solvents.Antioxidant properties were assessed by using 2,2’-diphenyl-1-picrylhydrazyl(DPPH),2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS)andβ-carotene bleaching assays.The antibacterial activity was evaluated on six standard bacterial strains using the agar disc diffusion method.The GC-MS analysis was performed using non-polar and polar capillary columns.Results:The chloroform extract of Caulerpa racemosa exhibited higher contents of polyphenols[(123.91±1.46)mg gallic acid equivalent/g dry extract]and tannins[(59.28±5.43)mg catechin equivalent/g dry extract](P<0.001)and was the most effective in scavenging DPPH[(1.98±0.08)mg/m L]and ABTS[(1.66±0.05)mg/m L]radicals.The hexane extract displayed the best antibacterial activity against Staphylococcus aureus,Bacillus cereus,and Pseudomonas aeruginosa,producing inhibition zones of(11.16±0.76),(9.00±0.00)and(9.33±1.15)mm,respectively.The l-(+)-ascorbic acid 2,6-dihexadecanoate and 4-hydroxy-2 methylproline were among the most abundant volatile compounds.Besides conventional fatty acids,cis-10-heptadecenoic acid,nonahexacontanoic acid,and dodecanoic acid,3-hydroxy-were identified.Two phytosterols were identified:stigmast-5-en-3-ol-(12.9%)and stigmast-5-en-3.beta.-ol,(24 S)-(4.57%).Conclusions:The preliminary identification of the volatile compounds reveals the presence of some new bioactive components not reported previously in Caulerpa racemosa from other geographical areas.Some of these compounds possess an interesting potential for pharmaceutical/nutraceutical applications.

Plant extracts as natural photosensitizers in photodynamic therapy:in vitro activity against human mammary adenocarcinoma MCF-7 cells

Objective: To examine three plant extracts [Lumnitzera racemosa(Combretaceae)(L.racemosa), Albizia procera(Fabaceae)(A.procera) and Cananga odorata(Annonaceae)] for their potential as source of photosensitizers in photodynamic therapy.Methods: Human mammary adenocarcinoma(MCF-7) cells were treated with the plant extracts, which were irradiated with 5.53 m W and 0.553 mW broadband light.Cell viability was assessed using MTT assay and induction of apoptosis was determined using terminal deoxynucleotidyl transferase-dUTP nick end labeling assay.Results: The crude ethanolic extracts, independently, were nontoxic against cancer and non-cancer cells but when irradiated with 5.53 mW broadband light, L.racemosa and A.procera extracts were cytotoxic against MCF-7 with IC_(50) of 11.63 mg/mL and10.73 mg/mL, respectively.With 0.553 mW broadband light, the IC_(50) values were higher at 17.14 mg/mL and 19.59 mg/mL, respectively.Photoactivated L.racemosa and A.procera extracts were found to be more cytotoxic against MCF-7 than the non-cancer cell line, human dermal fibroblast-neonatal.Moreover, the cytotoxicity of the extracts was mediated by apoptosis.Conclusions: Two of the plant extracts used, L.racemosa and A.procera were toxic and induced apoptosis to mammary cell adenocarcinoma, MCF-7 when photoactivated.These extracts were also more toxic to human cancer than non-cancer cell lines.

Ethnobotanical review and pharmacological properties of selected medicinal plants in Brunei Darussalam:Litsea elliptica,Dillenia suffruticosa,Dillenia excelsa,Aidia racemosa,Vitex pinnata and Senna alata

The aim of the current study is to review the medicinal properties of the plants found in Brunei Darussalam namely Litsea elliptica, Dillenia suffruticosa, Dillenia excelsa, Aidia racemosa, Vitex pinnata and Senna alata. The known phytochemical constituents of these plants and their ability to bring about a range of biological activities are included in this review. These plants have been used traditionally for a multitude of diseases and illnesses. There is a lot of untapped potential in these medicinal plants which could cure multiple diseases.

Improvement of Fermented Fish Flour Quality Using Essential Oil Extracted From Fresh Leaves of Pimenta racemosa(Mill.)J.W.Moore

The aim of this study was to evaluate the efficacy of the essential oil extracted from fresh leaves of Pimenta racemosa in the improvement of fermented fish flour producing technology.Essential oil of Pimenta racemosa was extracted by hydrodistillation and its chemical composition was determined by GC and GC/MS.Different types of fermented fish flours from Lesser African Threadfin(Galeoides decadactylus)were produced by the modification of the traditional processing technology and the introduction of a step of essential oil adjunction during the process.Three different essential oil concentrations(0.5,1.0 and 2.0 lL g^(-1))were investigated.Physicochemical,microbiological and nutritional analyzes were performed in order to evaluate the quality of the fermented fish flour produced.Results obtained revealed that the essential oil of Pimenta racemosa investigated has a chemical composition characterized by the presence of myrcene(25.1%),chavicol(7.5%)and eugenol(51.1%).Fermented fish flour produced have a good nutritional potential.However,on the microbiological level,only samples produced by adjunction of essential oil have a low level of microbial contamination,with an absence of pathogenic microorganisms.

Efficient, Season-Independent Seed Germination in Black Cohosh (<i>Actaea racemosa</i>L.)

Seed germination in black cohosh was systematically examined in eighteen populations including 15 USDA accessions with an effective protocol for the consistent, season independent germination of this valuable alternative specialty crop. Two in vitro approaches were investigated for breaking the complex double dormancy of black cohosh seeds for yearround germination of plants for increased cultivation and laboratory studies. The first approach was a two-step alternating temperature stratification in which surface sterilized seeds were incubated in darkness at 25?C for two weeks followed by incubation at alternating temperatures of 20?C and 8?C for 12-hour periods with a 16-hour photoperiod for 12 months. The second was a three-step-approach that involved initial stratification of seeds in darkness at 25?C for two weeks, followed by incubation at 4?C in darkness for 3 -4 months and then cultivation at 25?C with a 16-hour photoperiod to generate seedlings. Although both approaches broke double dormancy for black cohosh seed germination, the three-step-stratification technique yielded higher percentage seed germination in less time when compared to the two-step scheme, including for seeds stored over two years. Additional factors of critical importance for efficient germination included the selection of healthy and viable seeds, as well as thorough but non-excessive surface sterilization to control bacterial and fungal contamination. The in vitro approach for black cohosh germination allowed year-round cultivation and culture of a number of different genotypic accessions to enable laboratory based studies on cell culture and transformation approaches to aid in deciphering gene-metabolite relationships in this important medicinal plant.

Ecological and Chemotypic Analysis for Improved Growth and Management of Naturally Occurring Black Cohosh (<i>Actaea racemosa</i>L.) Populations in Western Maryland

Black cohosh (Actaea racemosa L.) is a perennial herb native to deciduous woodlands in eastern North America with an extensive history of traditional use, most commonly for rheumatoid arthritis and female reproductive issues. Modern clinical research has maintained this herb’s relevance into the 21st century with a majority of authentic black cohosh raw material still harvested from naturally occurring populations in Appalachian woodlands for use in botanical supplements. Increased use and interest in black cohosh have led to increased wild harvesting, reports of adulteration, and stress on this important natural resource. In an effort to study this significant medicinal plant as part of an ecosystem, and to understand factors that would contribute to the more effective growth and maintenance of black cohosh, key chemical, physiological, and ecological aspects of two occurring populations in western Maryland were surveyed. Rhizomes were harvested from six populations of naturally occurring black cohosh in two state forests located in the Allegheny Plateau and Ridge and Valley physiogeographic provinces of Maryland. The concentrations of five medicinal compounds found in black cohosh extracts, actein, 23-epi-26-deoxyactein, cafeic acid, ferulicacid, and N-methylserotonin, were compared with plant reproductive status as well as accompanying overstory and under story species, soil moisture, and soil pH at each site. Compound levels showed a complex dependence on physiography but were independent of reproductive state. The findings provide clues to guide efforts at effective growth and management of wild populations of black cohosh and other threatened medicinal plants.

聚果榕小蜂种内竞争的化学信息调节机制初探

昆虫种内普遍存在着对于交配机会、产卵场所以及食物资源的竞争,而具信息交流作用的化学物质在调节种内竞争中起着重要的作用。聚果榕(Ficus racemosa)的传粉榕小蜂Ceratosolen fusciceps存在着种内竞争,我们通过控制榕小蜂在果内能否互相接触(同时、间隔放蜂)的方法进行放蜂实验,同时用瘿花比例、种子比例、败育花数量和榕小蜂子代数量作为榕小蜂种内竞争的指标,并用顶空固相微萃取装置和气相色谱–质谱联用仪鉴定分析榕小蜂在雌花期进果前后,榕果和榕小蜂中的差异性挥发性成分,重点探讨这些物质在调节榕小蜂种内竞争中的作用。研究结果表明,同时放蜂所产生的瘿花比例、种子比例和榕小蜂子代数量相较于间隔放蜂显著偏低,而败育花数量则显著偏多;化学鉴定结果表明榕小蜂进果前后榕树的挥发性物质的种类存在差异,在鉴定出来的22种差异物质中,部分物质对其他种昆虫有抑制产卵的作用。因此,信息化学物质对榕小蜂的行为可能起着重要的调节作用,这种作用对于榕小蜂子代和寄主榕树适合度可能都具有重要影响。

Seasonal Changes in the Trade-off Among Fig-supported Wasps and Viable Seeds in Figs and Their Evolutionary Implications

Abstract: What the real trade-off is among fig-supported wasps and the viable seeds of figs is heatedly debated in the studies of fig/fig wasp mutualism. In the present study, we collected wasp offspring (galls) and the viable seeds of premature fruits, and determined the foundress number in receptive fruits and all the types of wasps supported by Ficus racemosa L. during both the rainy and dry seasons in Xishuangbanna, China. The data show that the galls were positively correlated with viable seeds (n= 32; r= 0.74; P < 0.001) when the proportion of vacant female flowers (PVFF) was high, in April (68.0%), and were negatively correlated with viable seeds (n= 48; r=?0.59; P < 0.05) when PVFF were limited (PVFF = 42.6%) during a colder month (January). The mean foundress number per fruit during the colder months is significantly lower than during the warmer months (F5, 603= 27.9; P < 0.001) and pollinator wasps can live longer during the colder months. During the colder months, the proportions of non-pollinators and wasp offspring are higher than those found during other months, whereas the proportion of viable seeds is not different compared with that of other months. Non-pollinator wasps tend to oviposit the female flowers that have been oviposited by pollinator wasps. The non-pollinators only negatively affect pollinator wasps and there is no obvious negative effect of non-pollinator wasps on viable seeds, so ovipositing by non-pollinator wasps will not result in the extinction of the figs during the process of evolution. The results of the present study indicate that figs can allow less foundresses to be in fruit cavities when PVFF are limited, which provides supporting evidence for the previous assumption that the plants have developed a mechanism to maintain a stable system because of the conflicts between the parties involved.

Fragmentation Effects on Diversity of Wasp Community and Its Impact on Fig／Fig Wasp Interaction in Ficus racemosa L.

Abstract: Habitat fragmentation usually results in alteration of species composition or biological communities. However, little is known about the effect of habitat fragmentation on the fig/fig wasp system. In this study, we compared the structure of a fig wasp community and the interaction between figs and fig wasps of Ficus racemosa L. in a primary forest, a locally fragmented forest and a highly fragmented forest. Our results show that, in the highly fragmented forest, the proportion of pollinator wasps is lower and the proportion of non-pollinator wasps is higher compared with the primary forest and locally fragmented forest. The proportion of fruits without pollinator wasps in mature fruits is also greatly increased in the highly fragmented forest. The proportion of galls in all female flowers increases in the highly fragmented forest, whereas the proportion of viable seeds does not change considerably. The disruption of groups of fig trees results in a decrease in pollinator wasps and even might result in the extinction of pollinator wasps in some extreme cases, which may transform the reciprocal interaction between figs and fig wasps into a parasite/host system. Such an effect may lead to the local extinction of this keystone plant resource of rain forests in the process of evolution, and thereby, may change the structure and function of the tropical rain forest.

Immunomodulatory effects of Caulerpa racemosa var peltata polysaccharide and its selenizing product on T lymphocytes and NK cells in mice

A polysaccharide, CrvpPS, was isolated from Caulerpa racemosa var peltata. It was reacted with nano-selenium in distilled water containing ascorbic acid (Vit C) to form a stable CrvpPS-nano-Se complex. The immunomodulatory effects of CrvpPS and CrvpPS-nano-Se on T lymphocytes subgroups and NK cells in mice were investigated. After intragastric administration for 10 days separately, both CrvpPS and CrvpPS-nano-Se showed significant stimulatory functions to thymus gland of mice. Moreover, the CrvpPS-nano-Se induced the percentage of CD3+, CD3+CD4+, NK cells and the CD4+/CD8+ value to increase significantly (P<0.05) when analyzed by flow cytometry, which is better than the CrvpPS, sucrose-nano-Se, and even the positive drug levamisole.

Ecological role of physical dormancy in seeds of Oxytropis racemosa in a semiarid sandland with unpredictable rainfall

Aims Seed dormancy and the soil seed bank are crucial to plant regeneration strategy,especially in semiarid ecosystems with unpredictable precipi-tation.the aim of this study was to investigate how seed dormancy is controlled by environmental factors and how it is correlated with the soil seed bank and regeneration of the perennial legume Oxytropis race-mosa,a dominant perennial herb in Mu Us Sandland of semiarid China.Methods Germination and imbibition experiments on fresh intact and scarified seeds of O.racemosa were used to identify physical dormancy(PY)in seeds of this species.Soil seed bank dynamics,timing of seedling emer-gence and the fate of buried seeds in the natural habitat were investigated.Important Findings PY was broken by mechanical scarification or wet heat/ice water cycles but not solely by dry heat or wet heat treatment.the soil seed bank exhibited seasonal changes in the number of seeds,which was highest in September and lowest in July.Seeds buried at different sand depths gradually lost dormancy;20-42%of the seeds remained dormant after 20 months of burial.Dormancy break occurs grad-ually throughout the year.Our results indicate that O.racemosa exhibits hardcoatedness heterogeneity that spreads germination of a seed cohort between seasons and years in the semiarid environ-ment,where the amount of precipitation during the growing season is highly variable.