ent-Labdane glycosides from the aquatic plant Potamogeton lucens and analytical evaluation of the lipophilic extract constituents of various Potamogeton species

Two new ent-labdane glycosides, one known furano-ent-labdane and a new hydroxylated fatty acid were isolated from the dichloromethane extract of the freshwater aquatic plant Potamogeton lucens. The new compounds were assigned the structures of beta-d-glucopyranosyl-8(17),13-ent-labdadien-16,15-olid-18-oate, 18-beta-d-glucopyranosyloxy-8(17),13-ent-labdadien-16,15-olide and 13(R)-hydroxy-octadeca-(9Z,11E,15Z)-trien-oic acid by spectroscopic means. The algicidal activity of these compounds was tested against Raphidocelis subcapitata. Based on our previous study of Potamogeton pectinatus, other constituents were identified in P. lucens by LC-UV-MS, LC-NMR and GC-MS. The lipophilic extract profiles of both species are presented. Two other species, Potamogeton perfoliatus and P. crispus, were also investigated by analytical comparison of their non-polar extracts. The distribution of ent-labdanes characterized in Potamogeton is summarized.     

Genetic structure and morphological variation of British populations of the hybrid Potamogeton x salicifolius

Potamogeton x salicifolius Wolfg. is one of the three most frequently recorded Potamogeton hybrids in the British Isles and Europe. It is thought to be the hybrid between P. lucens and P. perfoliatus. Its scattered distribution suggests that it has arisen several times in Britain. Most British populations of P. x salicifolius can be identified by their morphological characteristics, which are intermediate between those of the putative parents P. lucens and P. perfoliatus . However, the population at the Ouse Washes, Cambridgeshire, differs from other populations in its greater similarity to P . lucens . A genetic study of eight British populations, using six isozyme systems, revealed that most populations consist of a single multi-enzyme phenotype. This suggests that they were the result of a single hybridization event and are therefore maintained through vegetative reproduction. By contrast, the Ouse Washes population consists of three multi-enzyme phenotypes. This variation is likely to have resulted from multiple hybridization events, although we cannot exclude the possibility that the plants are partially fertile. The isozyme systems studied were unable to identify P. lucens and P. perfoliatus unambiguously, and consequently did not provide evidence for their putative parentage of P. x salicifolius. However, at a local level the banding patterns of the hybrids were generally consistent with the local multi-enzyme phenotypes of these putative parents.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 99–111.     

Genetic diversity and origin of Potamogeton anguillanus (Potamogetonaceae) in Lake Biwa,Japan

We analyzed the genetic variation in Potamogeton anguillanus Koidz. and its putative parents, P. malaianus Miq. and P. perfoliatus L., at five allozyme loci of four enzymes to test the hypothesis of a hybrid origin for P. anguillanus, collected in Lake Biwa, Japan. Alleles diagnostic for either P. malaianus or P. perfoliatus were present at four loci. Of 13 single locus phenotypes (SLPs) of P. anguillanus, eight were phenotypes that were expected in F(1) hybrids between P. malaianus and P. perfoliatus. Two SLPs were different from those expected in F(1) hybrids but could have resulted from segregation of parental alleles in later generation hybrids. Each of the remaining three SLPs possessed one allele unique to P. anguillanus. Allozyme analyses thus supported the view that P. anguillanus was derived from hybridization between P. malaianus and P. perfoliatus. It seems likely that the genetic diversity of P. anguillanus found previously originated through multiple hybridizations and sexual processes in P. anguillanus. Other processes such as intragenic recombination, mutation, or hybridization with another lineage are also discussed with reference to the origin of unique alleles.     

Molecular evidence for a natural primary triple hybrid in plants revealed from direct sequencing

BACKGROUND AND AIMS: Molecular evidence for natural primary hybrids composed of three different plant species is very rarely reported. An investigation was therefore carried out into the origin and a possible scenario for the rise of a sterile plant clone showing a combination of diagnostic morphological features of three separate, well-defined Potamogeton species. METHODS: The combination of sequences from maternally inherited cytoplasmic (rpl20-rps12) and biparentally inherited nuclear ribosomal DNA (ITS) was used to identify the exact identity of the putative triple hybrid. KEY RESULTS: Direct sequencing showed ITS variants of three parental taxa, P. gramineus, P. lucens and P. perfoliatus, whereas chloroplast DNA identified P. perfoliatus as the female parent. A scenario for the rise of the triple hybrid through a fertile binary hybrid P. gramineus x P. lucens crossed with P. perfoliatus is described. CONCLUSIONS: Even though the triple hybrid is sterile, it possesses an efficient strategy for its existence and became locally successful even in the parental environment, perhaps as a result of heterosis. The population investigated is the only one known of this hybrid, P. x torssanderi, worldwide. Isozyme analysis indicated the colony to be genetically uniform. The plants studied represented a single clone that seems to have persisted at this site for a long time.     

洱海底泥特性对七种沉水植物生长的影响

为研究洱海底泥特性对沉水植物生长的影响,采用不同比例洱海底泥与湖岸土壤掺混形成五种基质,并分别移栽苦草、黑藻、微齿眼子菜、马来眼子菜、光叶眼子菜、穿叶眼子菜和狐尾藻,进行为期70d的室外生长实验,结果表明不同基质对几种植物的影响具种间差异。（1）在基质为50%深层底泥+50%湖岸土壤（碳、氮、磷含量分别为31.59、0.334和0.095 mg/g）时,苦草、马来眼子菜和光叶眼子菜的株高最大;基质为100%深层底泥（碳、氮、磷含量分别为37.88、0.803和0.149 mg/g）时,黑藻、微齿眼子菜、穿叶眼子菜和狐尾藻的株高最大;（2）基质为100%深层底泥时,苦草、黑藻、微齿眼子菜、马来眼子菜和光叶眼子菜生物量增加最多且相对生长速率最大;基质为100%浅层底泥（碳、氮、磷含量分别为77.37、5.691和0.136 mg/g）时,穿叶眼子菜生物量增加最多,相对生长速率最大;狐尾藻在基质为50%浅层底泥+50%深层底泥（碳、氮、磷含量分别为49.27、2.005和0.131 mg/g）时生物量增加最多,相对生长速率最大;（3）基质为100%湖岸土壤（碳、氮、磷含量分别为22.06、0.327和0.231 mg/g）时,7种沉水植物均生长缓慢,生物量增加较少。综上所述,中营养底泥（碳、氮、磷含量分别为31.59-49.27、0.334-2.005和0.095-0.131 mg/g）更适合沉水植物生长,底泥中过高或过低营养都不利于沉水植物生长。     

Effects of ROS and caspase-3-like protein on the growth and aerenchyma formation of Potamogeton perfoliatus stem

Protoplasma - Aerenchyma formation plays an important role in the survival of Potamogeton perfoliatus in submerged environment. To understand the regulatory role of reactive oxygen species (ROS)...     

六种沉水植物的克隆生长特征

为构建种群动态模型以指导沉水植被修复工程实践, 研究采用同质园实验方法对6种常见沉水植物(竹叶眼子菜(Potamogeton wrightii)、眼子菜(P. distinctus)、光叶眼子菜(P. lucens)、穿叶眼子菜(P. perfoliatus)、扭叶眼子菜(P. intortifolius)和苦草(Vallisneria natans)的克隆生长模式进行了连续观测研究, 获取了分株形成速率、空间扩张速率、株高增加速率等种群扩张动态参数,及分株数、间隔子长度、分株高度等克隆构件特征参数。结果表明, 6种沉水植物的分株数从28d开始增长, 其中苦草的分株形成速率最高, 平均为1.09株/d, 分株形成最大速率出现在55d之后; 穿叶眼子菜和扭叶眼子菜的分株形成速率低于苦草, 但是高于竹叶眼子菜、眼子菜和光叶眼子菜, 最大速率出现在41d之后。虽然苦草的分株最多, 但是分株的株高最低, 其株高增长速率均值为0.2 cm/d。眼子菜属物种中竹叶眼子菜和眼子菜株高增长速率最高, 光叶眼子菜的株高增长速率和分株形成速率都最低。克隆系占据面积随时间的扩张速率为穿叶眼子菜(113.22 cm2/d)>扭叶眼子菜(71.70 cm2/d)>苦草(35.48 cm2/d)>竹叶眼子菜(12.09 cm2/d)>眼子菜(3.07 cm2/d)>光叶眼子菜(0.53 cm2/d)。此外, 研究还发现眼子菜属植物普遍表现出匍匐茎上“节”的形成, 而苦草则不具备这种特性, 匍匐茎“节”的形成及随之形成的不定根在眼子菜属植物空间扩张过程中具有重要的生态功能, 并在种群构建方面与苦草等其他物种发生分异。基于眼子菜属植物匍匐茎上的“节”可以形成跳跃性的分株, 在种群面积扩张方面更具优势; 而苦草形成分株的数量更多、速度更快, 在提高种群密度保障种群稳定方面更有优势。     

Identification of the polar constituents of Potamogeton species by HPLC-UV with post-column derivatization, HPLC-MSn and HPLC-NMR, and isolation of a new ent-labdane diglycoside

The polar extracts of Potamogeton pectinatus, P. lucens, P. perfoliatus and P. crispus (Potamogetonaceae) were analyzed by HPLC-UV-MS and their chromatographic profiles were very similar. The polar constituents of P. pectinatus were more exhaustively investigated by HPLC-UV with post-column derivatization, HPLC-MS(n) and HPLC-NMR, which allowed the on-line identification of various known flavones (dereplication). One of these compounds, luteolin 3'-O-glucoside, has never been characterized in the Potamogeton genus. The HPLC-UV-MS and HPLC-NMR analyses revealed also the presence of ent-labdane diterpene glycosides in the polar extracts of P. pectinatus and P. lucens and led to the isolation of a new ent-labdane diglycoside from P. pectinatus, beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-15,16-epoxy-12-oxo-8(17),13(16),14-ent-labdatrien-19-oate.     

几种水生植物种子萌发的聚集效应研究

以10种常见水生植物的种子为材料,研究了种子聚集对其萌发的影响。结果表明,水鳖科植物种子萌发对聚集的响应多为正效应：海菜花（Ottelia acuminata）、出水水菜花（O.emersa）、密刺苦草（Vallisneria denseser-rulata）、水鳖（Hydrocharis dubia）和无尾水筛（Blyxa aubertii）种子聚集后其最终萌发率显著提高;苦草（V.na-tans）和刺苦草（V.spinulosa）种子聚集后最终萌发率虽然没有显著提高,但是其萌发速率得到显著提高。种子聚集对穗花狐尾藻（Myriophyllum spicatum）的种子萌发有显著的抑制作用,而对穿叶眼子菜（Potamogeton perfo-liatus）和水麦冬（Triglochin palustre）的种子萌发无显著作用。水生植物的种子聚集萌发特性可能与其繁殖策略有关。水鳖科植物多进行有性繁殖或者有性繁殖比例较大,其种子也由于粘性物质的包裹为聚集分布,在野外聚集萌发的大量植株形成一个单一物种的斑块,这有利于迅速占领新生境。而穗花狐尾藻、穿叶眼子菜和水麦冬种群维持和扩张基本依靠克隆繁殖。     

Potamogeton praelongus in West Greenland

An extant population of the long-stalked pondweed Potamogeton praelongus is reported from West Greenland for the first time. However, endocarps of the species have been recovered from up to 3500 years old lake sediments, so the species has a long history in this region. The species must have arrived in West Greenland by long distance dispersal, probably by geese migrating from NW Europe.     

A Study on Pollen Morphology of Potamogeton,Zannichellia and Triglochin from China

The pollen morphology of 19 species in the genera Potamogeton, Zannichellia and Triglochin from China was examined under light and scanning electron microscopes. 1. Pollen characteristics (1) Potamogeton L. (Plate 1, 2:1-8) Pollen grains spheroidal, subspheroidal, rarely oblate or ovoid, (17-35)24.41×27.76(18-45)μm in size; anaperturate; exine 1-2μm thick, 2layered or obscure; crass-reticulate, reticulate or finely-reticulate under LM, distinctly reticulate under SEM; muri uniform or not uniform, smooth or granular, rarely with processes; bacula thicker or thinner at the intersection of muri. (2) Zannichellia L. (Plate 2:9) Pollen grains spheroidal, ,(20-26)23.1×24.15(21-27) μm in size; anaperturate; exine 1 μm thick, stratification obscure; nearly reticulate under LM, shallowly reticulate under SEM; luminae shallow, large and irregular, muri very thin and not uniform; bacula absent. (3) Triglochin L. (Plate 2:10-11) Pollen grains spheroidal or subspheroidal; (20-30)23.65×23.7(20-30) μm in size; anaperturate; exine about 1μm thick, stratification obscure, finely reticulate under LM, distinctly reticulate under SEM; luminae rather large or minute; muri uniform, with 1-2 lines of granules, bacula present or absent. 2. Pollen types of Potamogeton L. (1) Thin muri--thick bacula: Potamogeton pectinatus, P. intramongolicus, P. filiformis, P. pamiricus; (2) Uniform muri and bacula: 1) Large pollen subtype: Potamogeton crespus; 2) Medium-sized pollen subtype: Potamogeton heterophyllus, P. perfoliatus, P. distinctus, P. malaianus; 3) Minute pollen subtype: Potamogeton oxyphyllus, P. obtusifolius, P. lucens, P. cristatus, P. gramineus, P. octandrus, P. pusillus     

Seed and tuber banks of aquatic macrophytes in the Askö area, northern Baltic proper

Sediment samples from 5 stations in the northern Baltic proper, 6.5 o/oo S, were collected in April 1987 and the emergence of seedlings was recorded over 120 days in a greenhouse at 20°C. Total seedling densities varied from 0 to 3328 m^-2: and of seven species, Zannichellia palustris and Chara spp. were the most abundant among seedlings and sporelings, respectively. Several common macrophytes in the area were rare as seedlings and no seedlings were recorded for the most abundant angiosperms, Potamogeton pectinatus, Potamogeton perfoliatus and Ranunculus baudotii. Except for the few annual species, reproduction by seeds contributed little to the dynamics of the vegetation in the area and no correlation was found between vegetation composition and the seed bank. For perennial species the winter survival of vegetative propagules is the most important factor for vegetation dynamics.     

Photosynthetic carbon sources in somepotamogeton species

The ability of somePotamogeton species to use bicarbonate for photosynthesis was assayed by means of relative net photosynthetic rates in alkaline (bicarbonate) and acid (free CO₂) solutions with an equivalent amount of inorganic carbon. The results showedPotamogeton crispus, P. oxyphyllus, P. maackianus, P. perfoliatus, P. malaianus and the submerged leaves ofP. distinctus to be able to use bicarbonate ions for photosynthesis. To the contrary, the submerged leaves ofP. fryeri, which is an inhabitant of soft and acid waters, and the floating leaves ofP. distinctus were proven to be ‘non-users’ of bicarbonate ions. Furthermore, the relative photosynthetic rates were determined using natural waters with various carbon conditions. The dependence of photosynthetic performance on the free CO₂, pH and alkalinity of the waters is discussed in relation to carbon metabolism. Further it is suggested that the carbon conditions are ecologically significant in relation to the productivity and success of macrophyte species in natural habitats.     

Using DNA-based techniques to identify hybrids among linear-leaved Potamogeton plants collected in China

Itis well known that interspecific hybrids occur in the genus Potamogeton. The linear-leaved Potamogeton species commonly have highly variable morphological characteristics. Their hybrids often show similar vegetative characters to their parental species and their identification based solely on morphology is not always conclusive. In order to clarify whether there are any hybrids from the linear-leaved Potamogeton plants collected in China, we used internal transcribed spacers (ITS) of nuclear ribosomal DNA and chloroplast rbcL gene sequences to identify the hybrids. Using ITS sequence additivity, we identified four hybrids, namely R orientalis (Rpusillus × P.oxyphyllus),P.pusillus × P. berchtoldii, P. foliosus × P. octandrus, and P. cristatus × P. octandrus. The latter three hybrids should be considered as new hybrids in Potamogeton. The maternal parents of the four hybrids were confirmed using chloroplast rbcL gene sequences.     

The responses of littoral invertebrates to eutrophication-linked changes in plant communities

The decay of submerged macrophytes in lakes of high trophic level drastically limits the extent of habitat available to littoral invertebrates. The loss can be partially compensated by growth of filamentous algae. Our results show that macroinvertebrates typically associated with submerged macrophytes as well as planktonic crustaceans and rotifers occurred within algal mats at high densities.Aggregations of filamentous algae are usually short-term, with frequent appearances and disappearances. The rate of colonization of algal mats by invertebrates is rapid. In locations with a high degree of water exchange, animals colonize both living and decomposing algal mats at a similar rate, but in sheltered habitats, decomposing filamentous algae are colonized by a smaller number of animals.Comparison was made between the occurrence of invertebrate macrofauna on Chara spp., Potamogeton perfoliatus, P. lucens and Myriophyllum spicatum in several lakes. Although these macrophytes differ visibly in morphology and phenology, the number and composition of macroinvertebrates during summer was associated more closely with trophic state of a lake than with plant species.     

The impact of the crayfish Orconectes virilis on aquatic macrophytes

SUMMARY. 1. The impact of crayfish on the biomass, density and shoot morphology of four submersed plant species was examined under semi-natural conditions. Male or female crayfish ( Orconectes virilis ) were held for 5 weeks at biomasses of 0, 5, 10 or 18 g m⁻² (live weight) in twelve plastic pools (4.67 m², surface area) containing Potamogeton richardsonii, Myriophyllum exalbescens, Nuphar variegatum and Sparganium eurycarpum .
2. Crayfish significantly affected biomass, density and/or shoot morphology of all four macrophyte species. Differences in the effect of crayfish on macrophyte growth were related to plant species, crayfish sex and activity, and the abundance of alternative foods.
3. The effect of female crayfish on macrophyte growth was generally stimulatory. Myriophyllum and Potamogeton biomass, Potamogeton density and Myriophyllum length increased in the presence of female crayfish, possibly due to the reduction in herbivorous snails as a result of crayfish predation. In contrast, plant growth decreased in the presence of male crayfish: Myriophyllum, Nuphar and Potamogeton biomass, Myriophyllum and Sparganium density, and Sparganium and Poiamogeton length were reduced at male crayfish biomasses between 5 and 18 g m⁻².
4. These results indicate that even relatively low densities of crayfish can greatly affect the growth of submersed aquatic plants. Because of their ability to modify aquatic macrophyte, macroinvertebrate and, ultimately, fish communities, the introduction of crayfish into lakes where they do not occur could have a major effect on the structure and composition of the littoral zone.     

Accumulation of heavy metals in leaves of submerged hydrophytes (<Emphasis Type="Italic">Elodea canadensis</Emphasis> Michx. and <Emphasis Type="Italic">Potamogeton perfoliatus</Emphasis> L.) and their responses to the effect of the wastewater of a metallurgical plant

The accumulation of heavy metals (Cu, Ni, Zn, Mn, and Fe), parameters of the photosynthetic apparatus, and flavonoid content in leaves of two widespread species of submerged hydrophytes (Elodea canadensis Michx. and Potamogeton perfoliatus L.) from habitats with different levels of pollutions have been studied. The investigations are carried out in the surroundings of the metallurgical plant in the town of Revda, Sverdlovsk oblast, Russia (Revda River, upstream and downstream the confluence of the sewage). It is shown that hydrophytes from polluted habitats (impact site) differ from the plants of a less polluted zone (background site) by a higher accumulation of heavy metals (HMs), greater leaf thickness, and larger cells and chloroplasts. Plants from the polluted site are characterized by a high content of photosynthetic pigments, while flavonoid content in the leaves is lower. The identified trends indicate a high adaptive potential of these species of plants and their ability to inhabit in an aquatic environment polluted with metals and other pollutants.     

Evolution of pollination system and characters of stigmas in Najadales

Diverse ways of pollination, including aerial, epihydrophilous and hypohydrophilous ones occur in the Najadales. Although the knowledge of pollination biology in this order has been largely accumulated in recent years, most researchers ignored the role of stigmas in the pollination process. Based on the previous works, we supplemented observations on stigmatic characters and pollination mechanism in nine species from four families. The flowers of Aponogeton lakhonensis ( Aponogetonaceae ), Triglochin palustre ( Juncaginaceae), Potamogeton crispus, P. distinctus, P. gramineus, P. pectinatus, P. perfoliatus, P. pusillus (Potamogetonaceae), are all found to open above or on water surface. Stigmas in these species have a large surface area. Correspondingly, the pollen grains are all found to be globular. Of the eight species, except for P. pectinatus and P. pusillus, the remaining six obviously expose their stigmas out of the perianth. Another species , Najas marina (Najadaceae), has filiform stigmas and ellipsoidal pollen grains which can germinate in water before being transferred onto stigmas in natural conditions. Pollination takes place in this species strictly under water. The characters of pollen and stigmas could be divided into two types, and the pollination system is of two kinds of mechanisms of stigmas capturing pollen in the Najadales. The species with globular pollen grains have wide, large stigmas while those producing filiform or precocious pollen grains, which are likely to be captured by stigmas during the pollen dispersal by water currents, normally have filiform stigmas. It is inferred that various water stresses might have resulted in the diversification of pollinationsystem in the Najadales.     

Functional differences in epiphytic microbial communities in nutrient-rich freshwater ecosystems: an assay of denitrifying capacity

1. The denitrifying capacity of epiphyton was used to evaluate differences in the function of epiphytic microbial communities on submersed macrophytes in nutrient-rich freshwater ecosystems. The denitrifying capacity of epiphyton on Potamogeton perfoliatus shoots of different age and with different epiphytic abundances from a eutrophic lake was investigated in laboratory microcosms in the light and dark. Additionally, differences between epiphyton on shoots of Potamogeton pectinatus grown under different in situ nutrient and hydraulic conditions were investigated by examining their denitrifying capacity.
2. Denitrification was registered in well-developed epiphytic layers on both mature and senescent shoots in the dark, with activities 3- to 10-fold higher in the epiphytic communities of senescent shoots. No activity was detected on young shoots with sparse epiphyton or on shoots from which loosely attached epiphyton had been removed. Denitrification never occurred during illumination.
3. Even though the epiphytic abundance was similar in magnitude, the denitrifying capacity of epiphyton adapted to high nutrient loadings was about a hundred times higher than that of epiphyton adapted to lower nutrient levels. Additionally, epiphytic abundance and denitrifying capacity were higher at sites less exposed to wave turbulence or water currents, than at sites with more water turbulence.
4. The results illustrate how the hydraulic and nutrient conditions of the surrounding water affect both the quantity and function of epiphytic microbial communities in nutrient-rich freshwater ecosystems.     

茨藻目植物柱头特征与传粉系统的演化

茨藻目包含有风媒、水表水媒和水下传粉的多种传粉方式。在前人工作的基础上,补充了4科9 种植物的柱头特征和传粉机制的观察。该目花粉和柱头特征可分为两类,传粉系统表现出两种不同的柱头捕获花粉的机制。花粉为球形的种与其宽大的柱头相配;而那些花粉演化为丝状或花粉在水中具先期萌发能力的种,其花粉易被其丝状的柱头所捕获。此外,还推测了导致这个类群传粉系统分化的可能原因。