Endoplasmic reticulum and crystalline fibrils in the root protophloem of Nymphoides peltata

Endoplasmic reticulum in the root protophloem of Nymphoides peltata (S.G. Gmel.) O. Kuntze changes form as sieve elements differentiate. In immature sieve elements the individual endoplasmic reticulum (ER) cisternae form large irregular aggregates in the cytoplasm. In older immature sieve elements the ER aggregates are more ordered and membranes in them are convoluted. Although convoluted ER predominates in immature sieve elements the ER of the mature sieve elements consists mainly of flattened stacks of ER cisternae. Some of these stacks of ER may be derived from the existing convoluted ER. Crystalline fibrils first appear in the cytoplasm of the sieve element when the ER starts to aggregate. The crystalline fibrils move to the parietal layer of the sieve element along with the aggregates of ER. A possible ontogenetic relationship between ER and crystalline fibrils is discussed.Abbreviation ER endoplasmic reticulum     

Ethylene-induced growth and proton excretion in the aquatic plant Nymphoides peltata

In the presence of auxin, ethylene can promote growth in petioles of N. peltata (S.G. Gmel.) O. Kuntze. Acid buffer will also stimulate growth in the tissue and, in abraded petiole segments, ethylene-stimulated growth is accompanied by a marked acidification of the medium. Auxin stimulates growth in this tissue and, for various auxin and ethylene treatments, the amount of growth is closely correlated with the degree of medium acidification. The results are consistent with predictions of the ‘acid-growth’ theory, and provide the first evidence that ethylene acts by an ‘acid-growth’ mechanism.     

Reproduction strategies in introduced Nymphoides peltata populations revealed by genetic markers

To determine whether introduced Nymphoides peltata populations reproduced vegetatively or sexually, microsatellites were used to study the genetic structure of the species in Sweden. Leaves from 156 plants and seeds from 4 plants were sampled from 7 water-systems and analysed. A total of 10 genotypes were found among the 156 leaves. Seeds accounted for one additional genotype per seed. Lack of genetic variation and entirely vegetative reproduction dominated in the introduced N. peltata populations although sexual reproduction was found in one water-system. However, even where the species reproduced sexually, vegetative reproduction constituted an important part of the total reproduction.     

Interference between two floating-leaved aquatic plants: Nymphoides peltata and Trapa bispinosa

A 12-week microcosm experiment was conducted to identify the intraspecific and interspecific interference abilities of two floating-leaved aquatic plants Nymphoides peltata (Gmel.) O. Kuntze and Trapa bispinosa Roxburgh. N. peltata exerted a strong interspecific interferential effect on T. bispinosa, but the opposite was not apparent. There existed an intraspecific interferential effect of T. bispinosa on itself, although the interspecific interference of N. peltata was stronger. No apparent intraspecific interference was found among the individual plants of N. peltata. The removal of N. peltata had a positive impact on growth and performance of T. bispinosa, whereas no apparent impacts were found in the removal of T. bispinosa on growth and performance of N. peltata. Moreover, both the removal of N. peltata and T. bispinosa did not show apparent effects on growth of the remaining individuals of the species themselves. These results suggest that N. peltata has distinct interferential advantages over T. bispinosa and that this depends mainly upon the differences between the two species in morphology and life history.     

Zeta potential measurements of cell wall preparations from Regnellidium diphyllum and Nymphoides peltata

Abstract. Cell wall particles were prepared from the semi-aquatic plants Regnellidium diphyllum and Nymphoides peltata with minimum disruption to the integrity of the cell wall. The behaviour of freshly-prepared and frozen-thawed particles in a D.C. electric field was monitored with a microscope attached to video recording apparatus. From the respective particles mobility in a well-defined electric field. it was possible to determine their electrostatic potential and consequently estimate the corresponding surface charge density. Experiments were performed in media of different pH and cation concentration (ie, K⁺ Ca²⁺). A significant electronegative potential was found in cell wall preparations of both plants. Freezing and thawing further reduced the electrostatic potential for both plant species in all the media utilized for electrophoresis. A reduction of pH or an increase of the cation concentration was found to neutralize the electrostatic potential in a sigmoidal fashion. Ca²⁺ was more than 10 times more effective than K⁺ at neutralizing the apparent electrostatic potential of the cell wall preparations. Regnellidium was found to have a lower electrostatic potential than Nymphoides , although both responded in a similar manner to the various treatments. The possible relevance of the cell wall electrostatic potential, pH and [Ca²⁺] and particularly their inter-relationship is discussed for the two species of plants in terms of their differing growth responses to the ionic environment of the plant.     

Cytochemistry and Ultrastructure of the Mucilage Secreting Trichomes of Nymphoides peltata (Menyanthaceae)

The young developing leaves in the buds of Nymphoides peltataare covered by a hyaline mucilage. The mucilage contains freesugars, polysaccharides and proteins. The most abundant monosaccharidesof the polysaccharide fraction are arabinose and galactose.Therefore, the major component of the mucilage is probably anarabinogalactan or arabinogalactan protein. The mucilage issecreted by glandular trichomes. It is suggested that both thepolysaccharide and the protein fraction of the mucilage aretransported to the plasmamembrane by vesicles of the Golgi apparatus(granulocrine secretion). Secretory proteins are probably synthesizedin the rough endoplasmic reticulum and transported to the Golgiapparatus via transition vesicles. Polysaccharides were localizedin Golgi vesicles by ultracytochemistry. After exocytosis thesecretion is accumulated between the cell wall and the cuticle;this leads to the formation of protrusions on the outer wallsof the glandular cells. Finally, the cuticle is ruptured andthe secretion is released. The biological function of the mucilageis not known. Possibly the mucilage is a lubricant or a protectionfrom desiccation. Nymphoides peltata (S.G. Gmel.) O. Ktz., trichomes, mucilage secretion, cytochemistry, ultrastructure     

Ecology of ligninolytic fungi associated with leaf litter decomposition

Advances in our understanding of the decomposition processes in forest ecosystems over the past three decades have demonstrated the importance of lignin as a regulating factor in the decomposition of leaf litter. Consequently, increasingly more attention is being focused on the ecology of fungi associated with lignin decomposition. The aim of this review is to provide a critical summary of the ecology of ligninolytic fungi inhabiting leaf litter and forest floor materials. The review focuses on the following aspects of ligninolytic fungi: the taxonomic and functional diversity of ligninolytic fungi, the outcomes of interactions between ligninolytic fungi and other organisms, the activity and abundance of ligninolytic fungi measured by the production of bleached leaves and humus, the activity of ligninolytic enzymes in soil environments, the substratum and seral succession, spatial and temporal patterns in both mycelial abundance and species distribution, and the effect of environmental factors such as nitrogen deposition and global environmental changes on ligninolytic fungi. This review integrates the ecology, diversity, and activity of ligninolytic fungi into the context of an ecosystem in order to provide an understanding of the roles of ligninolytic fungi in decomposition processes. Takashi Osono is the recipient of the 11th Denzaburo Miyadi Award.     

The Effect of Petiolar Temperature upon the Translocation Rate of 137Cs in the Phloem of Nymphoides peltata

A fixed length of the petiole of Nymphoides peltata was subjectedto a variety of temperature treatments. A Q₁₀ is calculatedfor the velocity of flow, from the mass transport rate of ¹³⁷Csin the phloem at temperatures between 0 and 50?C. Associatedwith lowered temperatures there was a temporary interruptionof transport overriding the longer term temperature dependence.The characteristics of the interruption were dependent uponthe size of the temperature drop and the magnitude of the ‘new’temperature.     

Safe sites for establishment of Nymphoides peltata seedlings for recovering the population from the soil seed bank

The population of the endangered plant species Nymphoides peltata in Lake Kasumigaura, Japan, has been declining drastically recently, and seedlings that emerge from the remaining soil seed bank have entirely failed to establish. The decline has followed artificial control of the water level in the lake. To examine the environmental requirements at the seedling establishment stage, we investigated the survival and growth of emerged seedlings at various microsites on the lakeshore by manipulating environmental conditions such as exposure to waves, inundation, and light availability so as to include the conditions of the presumed safe sites. Seedling survival at the early stage was affected most by environmental variables relating to the susceptibility to inundation. Survival until seedling establishment was profoundly affected by light availability as well as by susceptibility to inundation. In all, 136 genets were established in quadrats less prone to inundation and with sufficient light availability, which is consistent with the presumed safe-site characteristics of the original water regime: bare ground exposed during the spring water-level drawdown. Recovering the original water regime with seasonal drawdown will be indispensable for recovering a self-sustainable population. However, as first-aid measures, active restoration efforts through adaptive management using the remnant soil seed bank are urgently needed before the soil seed bank becomes exhausted.     

Isolation and characterization of highly polymorphic microsatellites in the aquatic plant,Nymphoides peltata (Menyanthaceae)

Ten microsatellite loci were described for conservation design of a threatened clonal aquatic plant, Nymphoides peltata. The microsatellite loci obtained through the construction of an enriched library were polymorphic (2–6 alleles per locus) and exhibited high levels of observed (0.333–0.889) and expected (0.284–0.765) heterozygosities. All microsatellite loci were expected to be useful for identification of genets and evaluation of genetic diversity of this species.     

Influence of inbreeding depression on a lake population of Nymphoides peltata after restoration from the soil seed bank

The negative effects of inbreeding depression on fragmented small populations are likely to be expressed more strongly after restoration efforts if regeneration processes have been highly restricted in degraded habitats. We examined the potential influences of inbreeding depression on a population of Nymphoides peltata (Menyanthaceae) restored from the remnant soil seed bank. A hand-pollination experiment demonstrated self-compatibility of a single remaining homostyle genet and significant inbreeding depression in selfed progeny, especially in parameters related to seedling growth (–0.6 for biomass, and –0.4 for relative growth rate). Our genetic analysis indicated that the presumed number of parents contributing to the current soil seed bank was only 2–8 genets and that a single sib-family dominated at each of three sampling sites. The results also showed that the selfed progeny of the homostyle genet were overwhelmingly dominant at two sites (86.8 and 94.7%). As a result, the growth performance of the seed bank seedlings was significantly reduced, to a level as low as that of the selfed progeny. Active restoration efforts to minimize the negative effects of the genetic bottleneck and continuous monitoring based on genetic and demographic study are recommended.     

基于转录组测序信息的水生植物莕菜SSR标记开发

利用软件MISA对水生植物莕菜转录组测序所获得的79536条EST序列进行分析,共检测出12319个EST-SSR位点。在莕菜的EST-SSR中,二核苷酸和三核苷酸重复单元是主导类型,分别占总SSR的57.31%和30.87%,其中AG/CT、AAG/CTT分别是二、三重复单元类型的优势重复基元,分别占总SSR的29.76%和8.66%。随机挑选了130对EST-SSR引物对莕菜两个居群进行遗传多样性检测,结果发现：78对引物能扩增出清晰可分辨的条带,其中37对能成功检测出多态性,引物多态率为 47.44%。这些多态性引物共检测出114个等位基因,每个位点2~6个,平均3.08个。观测杂合度（H_o）及预期杂合度（H_e）分别在0.229~1.000和0.351~0.756之间,多态信息含量PIC值在0.286~0.698之间,平均达0.495。以上研究结果表明,通过莕菜转录组测序产生的EST数据来开发SSR标记是一种简单而高效的途径,这些新的SSR分子标记为研究莕菜的居群遗传多样性及其遗传结构提供了工具。     

Reproductive consequences of interactions between clonal growth and sexual reproduction in Nymphoides peltata: a distylous aquatic plant

Distyly is a sexual polymorphism in which plant populations contain two floral morphs differing in morphology and physiology. The dimorphism serves to promote animal-mediated cross-pollination between the floral morphs. Clonal propagation can interfere with the functioning of distyly by compromising intermorph pollinations, resulting in reduced fertility. Here, we investigate the relations between clonal growth and sexual reproduction in the aquatic macrophyte Nymphoides peltata (Menyanthaceae). Surveys of morph representation in 30 populations from five regions of China revealed that most populations exhibited strongly biased morph ratios and 30% contained a single floral morph. Experimental pollinations indicate that N. peltata possesses a strong dimorphic incompatibility system preventing self and intramorph fertilizations. An experiment involving the manipulation of morph ratios in an experimental population and an investigation in a natural population with strong morph substructure both provided evidence that compatible pollen dilution limits fertility. Despite constraints on the functioning of distyly in N. peltata we found no evidence for evolutionary changes to the heterostylous syndrome, as reported in Nymphoides, including populations of N. peltata in other parts of its geographical range.     

Calcium-Dependent Lamina Production of Nymphoides peltata (Gmel.) O. Kuntze (Menyanthaceae): Implications for Distribution

Nymphoides peltata (Gmel.) O. Kuntze, a nymphaeid macrophyte,occurs commonly in polder and fluviatile areas in large partsof Europe and Asia. In contrast to the nymphaeid macrophytesNymphaea alba L. and Nuphar lutea (L.) Sm., Nymphoides peltatais almost completely absent from poorly-buffered waters andis never found in acid water bodies. Transplantation experimentsin water bodies of varying alkalinity demonstrated that, irrespectiveof the sediment type, leaf production of Nymphoides did occurin poorly-buffered waters, but not in acid waters. Cultivation experiments showed that floating leaf developmentof Nymphoides peltata could only take place if sufficient calciumwas available in the water layer or in twice-demineralized water.Addition of calcium to an acid cultivation medium or to watercollected from an acid moorland pool resulted in leaf production.Growth of Nymphoides in acid waters is impossible due to insufficientcalcium concentrations in the water layer of such waters. Itis suggested that the absence of Nymphoides peltata in somepoorly-buffered water bodies is partly due to the spatial isolationfrom rivers and canals and the high frequence of desiccation.The restricted occurrence of Nymphoides peltata to well-bufferedalkaline waters is functionally more related to the calciumavailability than to the bicarbonate content. Key words: Aquatic macrophytes, distribution, Nymphoides peltata, leaf production, calcium, acid, poorly-buffered and alkaline water     

Ethylene and growth control in the fringed waterlily (Nymphoides peltata): Stimulation of cell division and interaction with buoyant tension in petioles

The effect of ethylene on petiole growth of the Fringed Waterlily (Nymphoides peltata (S.G. Gmelin) O. Kuntze) changes during leaf ontogeny. During early development (before expansion of laminae), ethylene causes an increase in both cell number and cell size; later in development, promotion of rapid cell expansion is the dominant effect. The early effects may contribute to the accommodation of new leaves to water columns of different depth. The later effects on cell expansion only are shown to contribute to the rapid accommodation of floating leaves when changes in water level submerge the laminae. This kind of accommodation results from an interaction between accumulated ethylene, which increases wall extensibility, and the tension in petioles due to natural buoyancy which, it is suggested, supplements the driving force for cell expansion. Cell age (position) within a petiole and age of the whole petiole influence the growth response to ethylene alone and the amount of extra growth produced by applying tension when ethylene is present. In young petioles, apical cells are highly sensitive to ethylene and tension causes little further growth; older cells in both immature and mature petioles show little response to ethylene unless the petiole is under tension. Young (but not mature) petioles respond slowly to applied tension even in the absence of ethylene. It is concluded that as cells age the driving force for expansion limits increasingly their capacity to respond to the wall-loosening effects of ethylene. Dual sensitivity to ethylene and buoyant tension facilitates rapid accommodation responses but sensitivity of young petioles to tension alone may exclude Nymphoides from habitats where current velocity is appreciable.     

Growth of three submerged plants below different densities of Nymphoides peltata (S. G. Gmel.) Kuntze

We evaluated one-sided competition from the floating-leaved plant Nymphoides peltata (non-indigenous in Sweden) on three submerged plant species, Ceratophyllum demersum, Elodea canadensis and Ranunculus circinatus, in a controlled experiment. The three submerged species were allowed to grow for 21 days in the absence of N. peltata and with the species present at densities of approximately 33, 66 and 100% cover. All species retained a positive relative growth rate (RGR) based on length at all N. peltata densities, but responded with negative growth based on weight for several treatments. C. demersum achieved RGR of 0.03 day⁻¹ in the absence of N. peltata, RGR of 0.02 day⁻¹ in the lowest N. peltata density but negative RGR in the two denser treatments. E. canadensis responded similarly with RGR of 0.04 day⁻¹ in the absence of N. peltata, RGR of 0.01 day⁻¹ in the lowest N. peltata density and negative RGR in the two denser treatments. R. circinatus, on the other hand, never achieved positive RGR based on weight. These results suggest that one-sided competition from floating-leaved plants has a profound effect on the submerged plant community.     

Acid phosphatase activity in intercellular spaces in roots of Nymphoides peltata (S. G. Gmel.) O. Kuntze

Abstract. Acid phosphatase was found cytochemically in intercellular spaces in the root of Nymphoides peltata. Different methods, using lead salts and azo-dyes, gave similar results. Reaction product appeared on material, possibly cytoplasmic, within the intercellular spaces and also against the outer walls of cells which formed the intercellular spaces. Possible functions of acid phosphatase in intercellular spaces are discussed.     

Sites of acid phosphatase in the differentiating root protophloem of Nymphoides peltata (S.G. Gmel.) O. Kuntze.

Abstract Sites of acid-phosphatase activity were found in the differentiating root protophloem of Nymphoides peltata by lead-salt and by azo-dye methods. Different substrates revealed different subcellular locations of the enzyme. The substrates β-glycerophosphate (β-GP) and naphthol ASBI phosphate revealed enzyme activity at similar sites within the sieve element. These sites included plasmodesmata, dictyosomes and small vacuoles in the cytoplasm. The substrate p-nitrophenylphosphate (p-NPP), however, revealed additional sites of acid-phosphatase activity which were not detectable by either naphthol ASBI phosphate or β-GP. For example, the inner region of the wall in mature sieve elements showed conspicuous acid-phosphatase activity only when p-NPP was used as substrate. The significance of the different locations of acid phosphatase within the sieve element is discussed. The convoluted ER, characteristic of immature sieve elements of N. peltata, failed to show acid-phosphatase activity whichever substate was used. By contrast, the stacked ER found in the parietal layer of mature sieve elements showed prominent acid-phosphatase activity regardless of the substrate used. The demonstration of acid-phosphatase activity in the stacked ER, and by both lead-salt and azo-dye methods, suggests that this organelle is a true site of acid-phosphatase activity. The onset of acid-phosphatase activity in the ER in later stages of sieve-element differentiation is compatible with the view that stacked ER plays a role in the final autolysis of the sieve-element protoplast.