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En México, la contaminación por elementos potencialmente tóxicos en el suelo y el agua representa importantes problemas ecológicos y de salud. Las plantas capaces de crecer en terrenos antropogénicamente modificados reflejan su capacidad de adaptación a diversas condiciones ambientales. La mayoría de los estudios de fitorremediación se lleva a cabo en condiciones de laboratorio, y sólo unos pocos estudios evalúan la capacidad de fitoextracción in situ. Esta revisión resume la información obtenida de fuentes científicas sobre los estudios de fitorremediación in situ realizados en México. El 85% de los estudios reportados corresponde a sitios contaminados con metales traza por actividades mineras. Se describen plantas con potencial para ser utilizadas como acumuladoras o hyperacumuladoras de elementos potencialmente tóxicos, como Hydrocotyle ranunculoides, Parietaria pensylvanica y Commelina diffusa para Zn; Rorippa nasturtium-aquaticum y Simsia amplexicaulis para Cu; Nicotina glauca, Flaveria angustifolia y Flaveria trinervia para As y Buddleja scordioides para la fitoremediación de suelos contaminados por Pb. Las especies de plantas nativas deben estudiarse para establecer mecanismos de fitoextracción de metales y la interacción agua-suelo-microorganismos para mejorar la eficiencia de la fitorremediación in situ. La información aquí descrita tiene utilidad para planificar la remediación de sitios contaminados por elementos potencialmente tóxicos en México y para diferentes sitios del mundo.

Hydrocotyle ranunculoides (Araliaceae) is an aquatic plant native to the Americas and invasive in Europe. This work reports laboratory and garden studies on the host range of its main natural enemy, the weevil Listronotus elongatus (Hustache) (Coleoptera: Curculionidae). The genus Hydrocotyle is in a disputed phylogenetic situation such that both Apiaceae and Araliaceae must be included in the test list, but lacking a clear criterion of phylogenetic proximity. For this reason three testing instances were applied: no-choice on excised leaves, no choice on functional plants, and a multiple choice garden experiment. A large initial test-plant list was reduced to a smaller list adjusted by a feeding intensity criterion, survival curves and oviposition levels. Feeding was observed on the excised leaves of 21 out of 36 test plants, but as tests progressed to whole plants L. elongatus showed it could only develop and thrive on its natural host, and possibly survive as adults on Hydrocotyle modesta. Results confirm that typical laboratory starvation tests can provide a dependable ranking of physiological acceptability of different plant species but severely overestimate the actual host range of a specialized herbivore. They also indicate that the phylogenetic criterion for test plant list construction must be approached cautiously if the phylogeny is uncertain or disputed.

Aquatic plants mostly disperse via vegetative means, and plant fragments are the most important vegetative dispersal units. Here we studied the fragment drift in the medium sized River Erft, in which the macrophyte community is dominated by alien aquatic plants. The plant fragments were sampled at six different sites in the drift of the river. We analyzed the drifting biomass, the number of fragments and the number of propagation units (based on the known minimum size of fragments needed for regeneration of each species) as potential propagation units. Overall, we sampled >13,000 drift units of various sizes, from short stem fragments 400 connected plants (Vallisneria spiralis), resulting in >500,000 propagation units. The total number of sampled drift units and propagation units were significantly higher for native than for alien plant species. The number of sampled drift units and biomass was correlated with the total plant mass (TPM, calculated from species abundances per river section and section lengths) of the species in the river. However, the highest numbers of drift and propagation units per unit TPM were found for the four natives Ceratophyllum demersum, Potamogeton pectinatus, Potamogeton crispus and Myriophyllum spicatum, contributing to more than 75 % of the total number of fragments sampled. Conversely, lowest numbers of drift units were found for alien plants Hygrophila polysperma and Hydrocotyle ranunculoides, and no drift units were collected for four aquatic plant species in the river (alien Myriophyllum aquaticum and natives Nuphar lutea, Potamogeton nodosus and Sparganium emersum).

Macrophyte mappings of a 37 km stretch of the thermally abnormal Erft River in 2003, 2005, 2007, 2011 and 2013 documented the presence of nine alien (Azolla filiculoides, Egeria densa, Eichhornia crassipes, Hydrocotyle ranunculoides, Hygrophila polysperma, Lemna minuta, Myriophyllum aquaticum, Pistia stratiotes and Vallisneria spiralis) in addition to 15 native species. During the study period, the number of native plant species decreased significantly in the river sections, while the number of alien species remained constant. The relative plant mass (RPM) of native species decreased from 67 to 33%, while that of the alien species increased. Only two of the nine reported alien species (V. spiralis and P. stratiotes) increased their abundances within the study period and became the most dominant species in the Erft River, while the other introduced species did not show mass development. The highest decline in RPM have been found for native Sparganium emersum and alien E. densa. Summarizing, the evergreen alien V. spiralis and recently P. stratiotes were the most successful invader within this thermally abnormal river since 2003, most likely profiting from the high winter temperatures >10 °C and displacing native vegetation, particularly formerly widespread native S. emersum.

The study was carried out to evaluate six different hydrophytes which were tested associated by twos: 1) Lemna gibba and Ceratophyllum demersum, 2) Berula erecta and Lemna gibba, 3) Polygonum punctatum and Hydrocotyle ranunculoides, and 4) Polygonum punctatum and Azolla filiculoides, for the purpose of removing nitrate from the water of Reyes Aztecas Lake, which is located southeast of Mexico City in Tlahuac District, Mexico D.F. The average of removal efficiency was obtained in relation to the different hydrophytes associations based on five sampling stations. The statistical analysis revealed that there were no significant differences among hydrophytes, all show remarkable ability to remove nitrate in water.

Crassula helmsii, Hydrocotyle ranunculoides, Ludwigia grandiflora and Myriophyllum aquaticum are four well known invasive aquatic plants in European waters. In this study, plant growth at different nutrient availabilities, regeneration capacity and photosynthesis were investigated. Results show high relative growth rates (RGR) of the species of up to 0.132 ± 0.008 g g -1 dry weight (dw) day -1 (H. ranunculoides) and a significant increase in RGR with increasing nutrient availability. All species show a high regeneration capacity and the ability to form new shoots from single nodes, even though it differs between the species. Ludwigia grandiflora and M. aquaticum also show regeneration from single leaves. Species differed in maximal amounts, and in temperature and light optima of net assimilation rates: H. ranunculoides leaves reach maximum photosynthetic rates of up to 3500 μmol CO 2 x h -1 g -1 dw, L. grandiflora (leaves) up to 2200 μmol CO 2 x h -1 g -1 dw, M. aquaticum (shoots) 400 μmol CO 2 × h -1 g -1 dw and C. helmsii (shoots) up to 200 μmol CO 2 x h -1 g -1 dw. Hydrocotyle ranunculoides, L. grandiflora and M. aquaticum preferred high light intensity and high temperatures, whilst C. helmsii was negatively affected by intense sunlight. Summarising, it can be assumed that at least H. ranunculoides, L. grandflora and M. aquaticum can grow well under current and likely future central European climate conditions.

Floating pennywort (Hydrocotyle ranunculoides L.f.), a member of the plant family Araliaceae originating from North America, is an example of an invasive aquatic species posing serious problems to the management of waterways outside of its original distribution area in Australia and Western Europe. As a consequence, its import was banned in the Netherlands. It can be difficult to distinguish H. ranunculoides from other species of the genus on a morphological basis. In this regard, DNA barcoding may become a good alternative once this could be performed on a routine basis. In this study, we show that it is possible to distinguish H. ranunculoides from a series of closely related congeners by using a single plastid DNA sequence, trnH-psbA.

Floating Pennywort (Hydrocotyle ranunculoides L. fil.) is a worldwide distributed aquatic plant. The species is native to North America and quite common also in Central and South America. In Europe, Japan and Australia it is known as an alien plant, sometimes causing serious problems for affected ecosystems and human use of water bodies. Starting from Western Europe with an eastwards directed spread, Floating Pennywort was recorded in Germany in 2004 for the first time. Since then, the species spread out and got established in western parts of Central Europe. For a definite prediction of the potential of a further spread, data about biology, in particular growth and photosynthesis are needed. Here, regeneration capacity, growth at different nutrient availabilities and photosynthesis of H. ranunculoides were investigated. In addition biomass samples were taken in the field. Results show an enormous regeneration capacity (e.g., by forming new shoots from small shoot fragments), increasing growth rates under increasing nutrient availability and a maximum increase of biomass reaching 0.132±0.008 g g−1 dw d−1. Dense populations of H. ranunculoides growing in ponds and oxbows were found at high nutrient content of the substrate, the biomass reaching there up to 532.4±14.2 g dw m−2. Gas exchange analysis showed a physiological optimum of H. ranunculoides CO2 uptake at temperatures between 25 and 35 °C and high photon flux densities (PPFD) above ∼800 μmol photons m−2 s−1. In comparison, native Hydrocotyle vulgaris showed an optimum of net photosynthesis at 20–30 °C and a light saturation of CO2 gas exchange at ∼350 μmol photons m−2 s−1.

WOS: 000263068700012, PubMed ID: 30764299, The discovery of exotic Ralstonia solanacearum biovar 1 strains on geranium in north Florida led to a concern that this strain may have become established. Therefore. we monitored irrigation ponds and potential alternative aquatic weeds from 2002 to 2005 for the presence of this strain. We report that this strain, possibly originating from the Caribbean, has become established in several ponds in Gadsden County, FL. Cladistic taxonomy was used to subclassify the bacterium at the species level into four groups or phylotypes based on multiplex polymerase chain reaction of the internal transcribed spacer (ITS) region. The bacterium was further divided into sequevars by sequencing the endoglucanase gene (egl). The strains were determined to belong to phylotype II/sequevar 4 NPB (nonpathogenic on banana) that was recently reported in Martinique. Partial sequencing of the egl followed by phylogenetic analysis placed the new Caribbean strains in a different clade than the typical Florida endemic strains. Pulsed-field gel electrophoresis (PFGE) revealed different haplotypes upon comparison of the collected pond strains and the Floridian strains. Based on PFGE polymorphism, egl sequencing, and phylogenetic analysis, the Caribbean strains were shown to be identical to the strain isolated from infected geranium plants. Experiments were undertaken to monitor R. solanacearum in irrigation ponds and associated weeds. R. solanacearum was detected in surface-disinfested common aquatic weeds growing in the irrigation ponds, including Hydrocotyle ranunculoides (dollar weed) and Polygonum pennsylvanicum (Pennsylvania smart weed). Both weeds were latently infected and showed no signs of wilt when collected. Two different Hydrocotyle spp. were artificially inoculated with R. solanacearum under greenhouse conditions and both developed symptoms 14 days post inoculation (dpi) and the bacterium was recovered from the tissues 42 dpi. There was a positive correlation between ambient temperature and R. solanacearum populations in irrigation water. as previously shown by other researchers.

Hydrocotyle ranunculoides L.f. is reported in this paper to be present at only 29 sites in the south east of England and in South Wales, in a wide range of water body types, which are typically slow-flowing and eutrophic. The current infestation is likely to have originated from various introductions from a single clone available at aquatic garden centres and nurseries in the U.K. Experiments on the optimum chemical control method have shown that the plant is most susceptible to the herbicide 2,4-D amine applied at 4.23 kg ha-1 active ingredient (a.i.). Initial observations suggest that the species is resistant to the herbicide glyphosate applied at 2.16 kg a.i. ha-1. This resistance is postulated to be due to insufficient uptake of the herbicide through the leaf cuticle.

Six new oleanane glycosides, ranuncosides I–VI, have been isolated from Hydrocotyle ranunculoides. Their structures have been determined on the basis of chemical and spectroscopic studies.

A further study of Physoderma hydrocotylidis from California on its host Hydrocotyle ranunculoides gives further details on its structure and development. EM micrographs reveal that the notably thin wall of the resting spore consists of an outer, an intermediate, and an inner layer. The complete wall thickness from measurements of these EM preparations is only 0.5 um, the thinnest of any known Physoderma resting spore. Such resting spores germinate readily in 2-5 h by the dehiscence of a broad cap and formation of a protruding endosporganium. Zoospores from the latter infect epidermal host cells and produce either the endobiotic, polycentric rhizoidal system with tenuous filaments, turbinate cells and eventually resting spores, or a hitherto unknown epibiotic, monocentric, rhizidiaceous sporangial stage. Zoospores from the latter may all bear colorless lipid globules or all faintly orange-colored ones. IN an earlier publication (Sparrow, 1968) a brief account was given of the obligate parasitic fungus Physoderma hydrocotylidis, first described from Brazil by Viegas and Teixeira (1943). Notes on its distribution in the Eastern United States and California, its appearance on the host leaves and germination of its resting spores were included in this account. No clear picture of its method of infection, polycentric endobiotic system on which the resting spores were formed, and no information on the monocentric epibiotic stage were given. Primarily, these considerable gaps in information were the result of the failure to obtain seedlings of the host which could be used to follow the development of the fungus from zoospore to zoospore in both stages; mature host tissue was too opaque to be of value in this respect. Recent studies, however, on the nearly transparent underwater bud scales of the Hydrocotyle, have obviated these difficulties and these essential features of the parasite were followed with great clarity. MATERIALS AND METHODS-Infected host material collected in California in 1967 and maintained in tanks at the University of Michigan Matthei Botanical Gardens was used in this study. Unopened leaf and floral buds together with a portion of the shoot just below the node bearing them were excised and placed in shallow dishes of charcoal water containing swimming R.S. (resting spore) zoospores of the fungus and left in daylight in damp chambers (petri dishes) at 22-26 C. These R.S. zoospores had been ob:'Received for publication 14 December 1976; revision accepted 15 May 1977. tained from resting spores of Physoderma teased out from infected, rotted blades and petioles of the host which had been lying in water. Such spores germinated readily in the dishes of charcoal water and provided an abundance of the zoospores aforementioned. At intervals, starting with 12 h of exposure tc R S. zoospores, bud scales were excised and ex amined for stages of the fungus, particularly for the epibiotic stage earlier suspected of being absent. This species of Physoderma is unique in my experience in the ease and speed with which its resting spores germinate. It will be recalled that it is the aggregation of these bodies, formed endophytically in the unhypertrophied but eventually killed local areas of host parenchyma, that produces the cinnamon brown to black pustules on petioles and leaves and occasionally on rhizomes of the host (Sparrow, 1968). These somewhat ellipsoidal to irregularly shaped resting spores, 15-25 /m x 12-16 /m, slightly flattened on one face, have two remarkable features. The first of these is an extremely thin, faintly brown wall, which, with a Filar micrometer eyepiece measured 0.8-0.9 /%m and from EM preparations was calculated as being even thinner (0.5 gm). This is the thinnest known wall of a Physoderma rest