可溶性无机氮在川蔓藻组织中的累积规律

近20年来,由于稳定性同位素无放射性、无污染、不受环境条件限制、无衰变且实验时间不受限制等优点,使稳定性同位素示踪方法作为一种了解复杂生态过程的工具,得到了广泛的应用[1-7].     

Structural characteristics of a diatom community epiphytic on Ruppia maritima

Epiphytic diatoms were collected from both the leaves and internodes of Ruppia maritima in a New Jersey salt marsh during the growing season of the host plant. Community diversity (H and the number of diatom taxa) values were initially high as Ruppia began its growth, but quickly dropped to sustained low levels as vegetative growth of the host ceased and new attachment sites were no longer available. A critical examination of all structural characteristics indicated that the leaves and internodes of Ruppia support a single, nearly homogeneous epiphytic diatom community. An analysis of variance indicated that differences between leaves and internodes were minimal, as did a comparison of the assemblages present on these two sites by a selected similarity index. A total of 57 taxa were encountered and the single dominant taxon was Navicula pavillardi, which accounted for one out of every three individuals counted. A comparison of the epiphytic diatom community with those inhabiting the sediments on the marsh proper revealed that the marsh sediments were the major source of individuals for Ruppia colonization.     

Comprehensive phylogenetic analyses of the Ruppia maritima complex focusing on taxa from the Mediterranean

Recent molecular phylogenetic studies reported high diversity of Ruppia species in the Mediterranean. Multiple taxa, including apparent endemics, are known from that region, however, they have thus far not been exposed to phylogenetic analyses aimed at studying their relationships to taxa from other parts of the world. Here we present a comprehensive phylogenetic analyses of the R. maritima complex using data sets composed of DNA sequences of the plastid genome, the multi-copy nuclear ITS region, and the low-copy nuclear phyB gene with a primary focus on the Mediterranean representatives of the complex. As a result, a new lineage, “Drepanensis”, was identified as the seventh entity of the complex. This lineage is endemic to the Mediterranean. The accessions included in the former “Tetraploid” entity were reclassified into two entities: an Asia–Australia–Europe disjunct “Tetraploid_α” with a paternal “Diploid” origin, and a European “Tetraploid_γ” originating from a maternal “Drepanensis” lineage. Another entity, “Tetraploid_β”, is likely to have been originated as a result of chloroplast capture through backcrossing hybridization between paternal “Tetraploid_α” and maternal “Tetraploid_γ”. Additional discovery of multiple tetraploidizations as well as hybridization and chloroplast capture at the tetraploid level indicated that hybridization has been a significant factor in the diversification of Ruppia.     

Shoot demography and morphology of Zostera japonica and Ruppia maritima from British Columbia,Canada

Shoot dynamics and morphology were studied in co-occuring intertidal populations of Zostera japonica Aschers. and Graebn. and Ruppia maritima L. s.l. in southwestern British Columbia. Repeated mapping and examination of cohorts of shoots (ramets) in permanent plots on a gradient in elevation showed that the appearance and loss of shoots, age structure, survivorship and leaf and rhizome dimensions were all affected by position on the gradient. For both species, the area having the greatest exposure t o air had fewer shoots and a greater percentage of shoots flowering early in the season. The duration of vegetative growth in R. maritima was the same regardless of elevation, while plants of Z. japonica at high elevation initiated and ended flowering and entered a quiescent overwintering state earlier than plants at lower elevation.     

沉水植物川蔓藻的生态学特征及其对环境变化的响应

川蔓藻是近海生态系统中重要的初级生产者, 了解它的生态学特征对于河口海岸带的生态修复具有重要意义。本文结合我们在天津滨海湿地生态修复工程中对于川蔓藻的研究成果, 从以下几个方面探讨了川蔓藻的生态学特征及其与环境的关系: 川蔓藻对极端环境因子的适应; 川蔓藻在资源分配上的繁殖策略; 川蔓藻的矿质营养代谢以及对栖息地生物地球化学循环的影响; 川蔓藻种群衰退的原因; 川蔓藻在环境修复中的应用。其中着重讨论了川蔓藻对环境变化的响应, 并结合我们的研究工作展望了它在环境工程与近岸水体修复中的应用潜力。     

沉水植物川蔓藻的生态学特征及其对环境变化的响应

川蔓藻是近海生态系统中重要的初级生产者,了解它的生态学特征对于河口海岸带的生态修复具有重要意义。本文结合我们在天津滨海湿地生态修复工程中对于川蔓藻的研究成果,从以下几个方面探讨了川蔓藻的生态学特征及其与环境的关系：川蔓藻对极端环境因子的适应;川蔓藻在资源分配上的繁殖策略;川蔓藻的矿质营养代谢以及对栖息地生物地球化学循环的影响;川蔓藻种群衰退的原因;川蔓藻在环境修复中的应用。其中着重讨论了川蔓藻对环境变化的响应,并结合我们的研究工作展望了它在环境工程与近岸水体修复中的应用潜力。     

Isolation of three new ent-labdane diterpenes from Dodonaea viscosa Jacquin (Sapindaceae): Preliminary evaluation of antiherpes activity

Investigation of the crude ethanolic extract obtained from the aerial parts of Dodonaea viscosa led to the isolation of three new ent-labdane diterpenes (1–3). The structures were established on the basis of their ESI–MS, UV, IR and NMR spectral data. The crude extract, fractions and compounds were evaluated for in vitro antiviral activity against Herpes Simplex Virus type 1 (HSV-1). The crude extract showed promising antiherpes activity expressed by a selectivity index of 6.2.     

ent-labdane glycosides from Baccharis pingraea.

The aerial parts of Baccharis pingraea, collected in Chile, afforded, in addition to two diterpene glycosides isolated previously, 14 new ones and two of the corresponding desacyl aglycones. The structures were elucidated by high field 1H NMR spectroscopy. The differences between the collections from Argentina and Chile are discussed.     

Antialgal furano-diterpenes from Potamogeton natans L

Six furano-ent-labdanes, 19-acetoxy-15,16-epoxy-8(17),13(16),14-ent-labdatrien-20-al, 15,16-epoxy-12-oxo-8(17),13(16),14-ent-labdatrien-20,19-olide, 12(S)-hydroxy-15,16-epoxy-8(17),13(16),14-ent-labdatrien-20,19-olide, 10alpha,19-dihydroxy-15,16-epoxy-8(17),13(16),14-nor-ent-labdatriene, 19,20-dihydroxy-15,16-epoxy-8(17),13(16),14-ent-labdatriene, 15,16-epoxy-12-oxo-8(17),13(16),14-ent-labdatrien-19,20-olide, were isolated, together with the known potamogetonin, from the aquatic plant Potamogeton natans. Their structures were determined on the basis of their chemical and spectral data. The compounds showed in vitro phytotoxicity against Raphidocelis subcapitata, a microalga used in aquatic tests.     

Protocols for Use of Potamogeton perfoliatus and Ruppia maritima Seeds in Large‐Scale Restoration

Restoration of submerged aquatic vegetation from seed has been hampered by a lack of information on the appropriate conditions for collecting, processing, and storing seeds prior to dispersal. Seeds must be processed and stored under conditions that maintain seed viability, meet dormancy requirements, and prevent premature germination. This study examined the effects of collection date, processing technique, aeration, storage and induction temperature and salinity, and storage period on seed germination of two mesohaline aquatic species, Potamogeton perfoliatus and Ruppia maritima. Collection date and processing technique were significant factors affecting seed yield from donor populations. Seeds of both species remained viable and germinated best when stored at 4°C, and then exposed to freshwater induction conditions. However, their responses to other factors differed. Aeration during storage was necessary in order to maintain viability of P. perfoliatus seeds, whereas it was unnecessary for R. maritima seeds. Storage in freshwater at 4°C prevented germination of P. perfoliatus seeds, while high salinity during cold storage was necessary to minimize premature germination of R. maritima. Mean germination time of P. perfoliatus was dependent on storage salinity; in contrast, mean germination time of R. maritima seeds was dependent on induction salinity. These differences indicate that the methods required to produce large quantities of underwater plant seed amenable to large‐scale restoration efforts must be tailored to the specific requirements of individual species and must consider the range of processes from initial harvest through seed testing prior to field establishment.     

Morphogenetic lability of reproductive structures in Ruppia maritima (Ruppiaceae, Alismatales): from two lateral flowers to a terminal flower

Flowers of Ruppia are normally arranged into an open two-flowered spike, but sometimes the two lateral flowers are congenitally united with each other and form a terminal flower-like structure. This developmental abnormality resembles those described in well-investigated mutants of model organisms of developmental genetics such as Arabidopsis Antirrhinum. A study of Ruppia allows investigating morphogenetic lability of this feature in natural populations. These data will be important for understanding evolutionary transitions between open and closed inflorescences. This paper presents first data on frequencies ofterminal flower-like structures in natural populations of Ruppia maritima and first observations of their development. Vascular supply of inflorescences with free and united flowers is compared for the first time. Strong differences in frequencies of occurrence of terminal flower-like structures among examined natural populations are revealed. Data on variation of organ numbers in flowers of plants from different populations allow hypothesizing that increased size of floral primordia is a factor that plays a role in their amalgamation into ajoint primordium of a terminal structure. Vascular system of inflorescences of R. maritima with united flowers is quite similar to the vascular system of a flower and nothing contradicts a hypothesis on terminal position ofthis structure. Transversally inserted stamens in inflorescences with united flowers are usually of inverted polarity. This appears to be the first documented example of an inversion of relative polarity of stamens and carpels in angiosperms.     

Waterbird impacts on widgeongrass Ruppia maritima in a Mediterranean wetland: comparing bird groups and seasonal effects

We studied the effect of waterbirds on the submerged macrophyte Ruppia maritima in eleven fish ponds within Doñana Natural Park (SW Spain). Separate exclosure designs allowed us to exclude flamingos or all waterbirds from 3×3 m plots within the ponds and compare them with control plots. Four experiments were conducted for three month periods at different points of the annual cycle with varying bird densities. Flamingos and wildfowl (ducks and coot) had significant negative additive effects on the presence of aboveground (leafs and shoots) or belowground (roots) parts of Ruppia at all times of the year. For plots where Ruppia was present, aboveground biomass was significantly higher in all-bird exclosures than in controls or flamingo exclosures. Presence and biomass of this annual plant varied significantly between seasons as did the density of seeds in sediments. Seasonal changes in seedbank densities were consistent with consumption by birds. There were no significant treatment×season interactions for Ruppia presence, aboveground biomass or seeds. This is the first exclosure study to compare the effects of waterbirds on submerged macrophytes at different times throughout the annual cycle, and the first to compare simultaneously the effects of different bird groups. Our findings refute previous suggestions that major effects of waterbirds are limited to temperate regions and to periods of early growth or when major concentrations of migratory wildfowl are formed in autumn. Flamingos are important in structuring shallow wetlands in the Mediterranean, and possibly many other regions.     

Photosynthetic temperature acclimation in two coexisting seagrasses,Zostera marina L. and Ruppia maritima L.

The physiological responses to temperature were investigated in two coexisting seagrasses, Zostera marina L. and Ruppia maritima L. sensu lato from the lower Chesapeake Bay, Virginia. Seven plant collections were made from March to July, 1983 at ambient temperatures of 8–30°C. Both species maintained relatively constant fresh: dry weight ratios and chlorophyll a:b ratios over the five-month period. Total chlorophyll content remained constant in Z. marina while that of R. maritima doubled from March to July. P_max values for both species increased with increasing temperature and declined at temperatures above 19 and 23°C (Z. marina and R. maritima, respectively). P_max values were significantly higher for R. maritima compared to Z. marina at temperatures above 19°C. Both short-term (laboratory) and long-term (in situ) responses to temperature regimes affected estimates of the photosynthetic capacity of both species. Thus, temperature histories of experimental material should be carefully considered when interpreting temperature effects on photosynthesis. This study provides support of the hypothesis that seasonal community dynamics of Z. marina and R. maritima in Chesapeake Bay are regulated in part by different responses to light and temperature.     

Bioconversion of Stemodia maritima diterpenes and derivatives by Cunninghamella echinulata var. elegans and Phanerochaete chrysosporium

Stemodane and stemarane diterpenes isolated from the plant Stemodia maritima and their dimethylcarbamate derivatives were fed to growing cultures of the fungi Cunninghamella echinulata var. elegans ATCC 8688a and Phanerochaete chrysosporium ATCC 24725. C. echinulata transformed stemodin (1) to its 7alpha-hydroxy- (2), 7beta-hydroxy- (3) and 3beta-hydroxy- (4) analogues. 2alpha-(N,N-Dimethylcarbamoxy)-13-hydroxystemodane (6) gave 2alpha-(N,N-dimethylcarbamoxy)-6alpha,13-dihydroxystemodane (7) and 2alpha-(N,N-dimethylcarbamoxy)-7alpha,13-dihydroxystemodane (8). Stemodinone (9) yielded 14-hydroxy-(10) and 7beta-hydroxy- (11) congeners along with 1, 2 and 3. Stemarin (13) was converted to the hitherto unreported 6alpha,13-dihydroxystemaran-19-oic acid (18). 19-(N,N-Dimethylcarbamoxy)-13-hydroxystemarane (14) yielded 13-hydroxystemaran-19-oic acid (17) along with the two metabolites: 19-(N,N-dimethylcarbamoxy)-2beta,13-dihydroxystemarane (15) and 19-(N,N-dimethylcarbamoxy)-2beta,8,13-trihydroxystemarane (16). P. chrysosporium converted 1 into 3, 4 and 2alpha,11beta,13-trihydroxystemodane (5). The dimethylcarbamate (6) was not transformed by this microorganism. Stemodinone (9) was hydroxylated at C-19 to give 12. Both stemarin (13) and its dimethylcarbamate (14) were recovered unchanged after incubation with Phanerochaete.     

Seasonal growth and reproduction of Ruppia maritima L. s.l. in Lake Pontchartrain,Louisiana, USA

Ruppia maritima L. s.l. is an important submerged aquatic plant in Lake Pontchartrain, a water quality impaired oligohaline estuary located north of New Orleans, Louisiana, USA. Efforts to restore Lake Pontchartrain are in progress, and a major restoration goal is the re-establishment of historic submerged macrophyte beds that have declined since first studied in 1953. This study was part of a long-term monitoring program to distinguish natural from anthropogenic causes of macrophyte population changes. Ruppia populations were monitored monthly for a 2-year period to obtain information on seasonal growth, peak biomass periods, flowering, seed production, and germination. We found that Lake Pontchartrain R. maritima had relatively high peak biomass and two seasonal peaks of biomass and flowering due to high water temperature and absence of competition from other macrophytes. However, biomass peaks were often disrupted by storms. Shoot biomass was high from May through November, and low from December through April. Spring shoot growth from seeds, roots, and rhizomes was rapid. Plants matured and produced abundant inflorescences and seeds between May and October. Reproductive shoots bearing seeds were detached in May and June. Remaining shoots formed dense beds through vegetative propagation during the summer. Turion production occurred during the winter.     

Effects of Planting Depth,Sediment Grain Size,and Nutrients on Ruppia maritima and Potamogeton perfoliatus Seedling Emergence and Growth

Protocols are now available for seed harvest, storage and germination of several mesohaline and polyhaline species; however, low seedling survival rates point to the need for an increased understanding of factors affecting seedling establishment. Depth of seed burial in sediments and initial seedling growth rates are shown to be limiting factors for photosynthetic competency of Ruppia maritima and Potamogeton perfoliatus. Seedling emergence is inversely proportional to planting depth on sediments ranging in grain size from coarse sands (850 μm) to silt (63 μm). Less than 6% of the seeds of either species emerged when buried to a depth of 3 cm in test sediments. Germination was greatest for seeds placed on the surface of sediments; however, these seedlings were subject to displacement because of the weak and fragile roots produced during early growth. Fine sediments may be more favorable for R. maritima seedling establishment, because seedling emergence and height decreased with increasing sediment grain size. Potamogeton perfoliatus seedlings seem to be more tolerant of a wider range of sediment grain sizes than R. maritima as indicated by the lack of an effect of sediment grain size on P. perfoliatus seed emergence, seedling height, and biomass. Increasing nutrients stimulated seedlings of both species; however, even at the highest concentrations tested, growth, as determined by shoot elongation and leaf and root formation, slowed within 7–10 days. This suggests factors other than mineral nutrients and light limit growth or that growth shifts from aboveground biomass production to belowground vegetative spread.     

Sesquiterpene lactones from Artemisia maritima

Two new sesquiterpene lactones have been isolated from Artemisia maritima and the structures have been assigned on the basis of their spectral properties as 1-oxo-6β,7α,11βH,14β-methylgermacra-4(5)-ene-12,6-olide and 1-oxo-6β,7α,11βH-germacra-4(5),10(14)-dien-12,6-olide.     

Oxepane diterpenes from montanoa tomentosa

The leaves of Montanoa tomentosa afforded a new oxepane diterpene, tomentanol, and its previously known relatives zoapatanol, montanol, tomexanthin and tomentol. The structure of tomentanol was determined through examination of its spectroscopic properties.