Growth performance and emergence of invasive alien Rumex confertus in different soil types.

Rumex confertus is known to be one of the most serious invasive weed species infesting meadows, pastures and ruderal lands throughout the Central Europe. Rumex confertus was grown in pot experiments using 8 soil types at 5 concentrations of nitrogen (N) and phosphorus (P). Based on harvest data, the variables, seedlings emergence, root: shoot (R: S) ratio, N and P concentration, chlorophyll content, Relative Colimitation Index (RCI) and dry matter allocation to plant components, were determined. N and P addition stimulated the growth of plants in different soils, as reflected by a significant increase in seedling growth parameters such as total plant biomass and shoot biomass. Across all soil types, emergence of seedlings was negatively affected by very high N, but positively affected by increased P availability. This study indicates that Dystric Arenosol, Entic Podzol, Brunic Arenosol and Calcaric Leptosol are unfavorable for R. confertus growth, excluding  R. confertus completely. Moreover, evidence suggests that plant growth is limited by both N and P, therefore R. confertus could be controlled by reducing available N and P content in the soil.

Overexpression of a flower-specific aerolysin-like protein from the dioecious plant Rumex acetosa alters flower development and induces male sterility in transgenic tobacco.

Sex determination in Rumex acetosa, a dioecious plant with a complex XY1 Y2 sex chromosome system (females are XX and males are XY1 Y2 ), is not controlled by an active Y chromosome but depends on the ratio between the number of X chromosomes and autosomes. To gain insight into the molecular mechanisms of sex determination, we generated a subtracted cDNA library enriched in genes specifically or predominantly expressed in female floral buds in early stages of development, when sex determination mechanisms come into play. In the present paper, we report the molecular and functional characterization of FEM32, a gene encoding a protein that shares a common architecture with proteins in different plants, animals, bacteria and fungi of the aerolysin superfamily; many of these function as ß pore-forming toxins. The expression analysis, assessed by northern blot, RT-PCR and in situ hybridization, demonstrates that this gene is specifically expressed in flowers in both early and late stages of development, although its transcripts accumulate much more in female flowers than in male flowers. The ectopic expression of FEM32 under both the constitutive promoter 35S and the flower-specific promoter AP3 in transgenic tobacco showed no obvious alteration in vegetative development but was able to alter floral organ growth and pollen fertility. The 35S::FEM32 and AP3::FEM32 transgenic lines showed a reduction in stamen development and pollen viability, as well as a diminution in fruit set, fruit development and seed production. Compared with other floral organs, pistil development was, however, enhanced in plants overexpressing FEM32. According to these effects, it is likely that FEM32 functions in Rumex by arresting stamen and pollen development during female flower development. The aerolysin-like pore-forming proteins of eukaryotes are mainly involved in defence mechanisms against bacteria, fungi and insects and are also involved in apoptosis and programmed cell death (PCD), a mechanism that could explain the role of FEM32 in Rumex sex determination.

Plant trait expression responds to establishment timing.

Trait divergence between co-occurring individuals could decrease the strength of competition between these individuals, thus promoting their coexistence. To test this hypothesis, we manipulated establishment timing for four congeneric pairs of perennial plants and assessed trait plasticity. Because soil conditions can affect trait expression and competition, we grew the plants in field-collected soil from each congener. Competition was generally weak across species, but the order of establishment affected divergence in biomass between potmates for three congeneric pairs. The type of plastic response differed among genera, with trait means of early-establishing individuals of Rumex and Solanum spp. differing from late-establishing individuals, and trait divergence between potmates of Plantago and Trifolium spp. depending on which species established first. Consistent with adaptive trait plasticity, higher specific leaf area (SLA) and root-shoot ratio in Rumex spp. established later suggest that these individuals were maximizing their ability to capture light and soil resources. Greater divergence in SLA correlated with increased summed biomass of competitors, which is consistent with trait divergence moderating the strength of competition for some species. Species did not consistently perform better in conspecific or congener soil, but soil type influenced the effect of establishment order. For example, biomass divergence between Rumex potmates was greater in R. obtusifolius soil regardless of which species established first. These results suggest that plant responses to establishment timing act in a species-specific fashion, potentially enhancing coexistence in plant communities.

Influences on the establishment and dominance of vegetation in stormwater infiltration basins.

Infiltration basins are widely used in urban environments as a technique for managing and reducing the volume of stormwater. These basins can be spontaneously colonized by wild plants, which can be used as bioindicators of edaphic characteristics. As the basins are anthropogenic environments, the description of plant biodiversity allows the determination of which species colonize such environments and identification of the relationships between plants, basin type and operation. Nineteen infiltration basins were selected according to their catchment types (industrial, urban, agricultural). The dominant species were identified and sampled. Rumex sp., Taraxacum sp. and Artemisia sp. are the three types most represented (88, 61 and 55% respectively of the basins studied). Their families and their respective orders are those most commonly found (Caryophyllales, Asterales and Polygonaceae, Asteraceae). Poaceae is the family grouping with the largest number of different species (11). Although each species occupies only 1 or 2 basins, plants of this family occupy 61% of the basins. Although the catchment characteristics of the 19 basins do not play a direct role in the diversity of plant families, they can influence the presence or absence of certain species. Thus, these plants can be used as bio-indicators of basin soil and operating characteristics, such as sediment depths, inundation frequency and duration.

Uptake and translocation of Ti from nanoparticles in crops and wetland plants.

Bioavailability of engineered metal nanoparticles affects uptake in plants, impacts on ecosystems, and phytoremediation. We studied uptake and translocation of Ti in plants when the main source of this metal was TiO2 nanoparticles. Two crops (Phaseolus vulgaris (bean) and Triticum aestivum (wheat)), a wetland species (Rumex crispus, curly dock), and the floating aquatic plant (Elodea canadensis, Canadian waterweed), were grown in nutrient solutions with TiO2 nanoparticles (0, 6, 18 mmol Ti L(-1) for P. vulgaris, T. aestivum, and R. crispus; and 0 and 12 mmol Ti L(-1) for E. canadensis). Also examined in E. canadensis was the influence of TiO2 nanoparticles upon the uptake of Fe, Mn, and Mg, and the influence of P on Ti uptake. For the rooted plants, exposure to TiO2 nanoparticles did not affect biomass production, but significantly increased root Ti sorption and uptake. R. crispus showed translocation of Ti into the shoots. E. canadensis also showed significant uptake of Ti, P in the nutrient solution significantly decreased Ti uptake, and the uptake patterns of Mn and Mg were altered. Ti from nano-Ti was bioavailable to plants, thus showing the potential for cycling in ecosystems and for phytoremediation, particularly where water is the main carrier.

Phytoextraction and uptake patterns of weathered polychlorinated biphenyl-contaminated soils using three perennial weed species.

Three promising phytoextracting perennial weed species [ L. (ox-eye daisy), L. (curly dock), and L. (Canada goldenrod)] were planted in monoculture plots at two polychlorinated biphenyl (PCB)-contaminated sites in southern Ontario and followed over 2 yr to investigate the effects of plant age, contaminant characteristics, and species-specific properties on PCB uptake and accumulation patterns in plant tissues. Results from this study indicate that, for each of these weed species, shoot contaminant concentrations and total biomass are dependent on plant age and life cycle (vegetative and reproductive stages), which affects the total amount of PCBs phytoextracted on a per-plant basis. Even at suboptimal planting densities of 3 to 5 plants m, all three weed species extracted a greater quantity of PCBs per unit area (4800-10,000 µg m) than the known PCB-accumulator L. ssp (cv Howden pumpkins) (1500-2100 µg m) at one of the two sites. Calculated PCB extractions based on theoretical optimal planting densities were significantly higher at both sites and illustrate the potential of these weeds for site remediation. This study also demonstrates that plants may accumulate PCBs along the stem length in a similar manner as plants.

[Study on correlation of soil nutrients and content of active constituents in root of Rumex gmelini].

OBJECTIVE: To provide scientific basis for the selection of agrotype and property fertilization for Rumex gmelini cultivated in compliance with good agricultural practice (GAP). METHOD: HPLC method was applied to determinate the content of seven active constituents (resveratrol, polydatin, chrysophanol 1-glucoside, nepodin, emodin, chrysophanol and physcion) of annual R. gmelini. And the correlation between soil nutrients and content of active constituents in the root of R. gmelini were analyzed by stepwise regression analysis. RESULT: Seven regression equation were established. The statistic significance was found in three of them. CONCLUSION: The soil with high total K level is not suitable for R. gmelini cultivation. But the higher available N, available P, available K level of soil is suitable.

Phytotoxicity of volatile oil from Eucalyptus citriodora against some weedy species.

A study was undertaken to explore the phytotoxicity of volatile essential oil from Eucalyptus citriodora Hook. against some weeds viz. Bidens pilosa, Amaranthus viridis, Rumex nepalensis, and Leucaena leucocephala in order to assess its herbicidal activity. Dose-response studies conducted under laboratory conditions revealed that eucalypt oils (in concentration ranging from 0.0012 to 0.06%) greatly suppress the germination and seedling height of test weeds. At 0.06% eucalypt oil concentration, none of the seed of test weeds germinated. Among the weed species tested, A. viridis was found to be the most sensitive and its germination was completed inhibited even at 0.03%. Not only the germination and seedling growth, even the chlorophyll content and respiratory activity in leaves of emerged seedlings were severely affected. In A. viridis chlorophyll content and respiratory activity were reduced by over 51% and 71%, respectively, even at a very low concentration of 0.06%. These results indicated an adverse effect of eucalypt oils on the photosynthetic and energy metabolism of the test weeds. A strong negative correlation was observed between the observed effect and the concentration of eucalypt oil. Based on the study, it can be concluded that oil from E. citriodora possess strong inhibitory potential against weeds that could be exploited for weed management.

[Study on the optimal harvesting time of Rumex gmelini by analyzing the contents of principal components].

OBJECTIVE: To establish a method used for optimization of harvesting time and determine the best time for harvesting Rumex gmelini. METHOD: An HPLC method was applied to determinate the contents of seven active constituents(resveratrol, polydatin, chrysophanol 1-glucoside, nepodin, emodin, chrysophanol and physcion)of R. gmelini at different development stage. The result was analyzed by principal component analysis. RESULT: The accumulation of active constituents showed a regular pattern. CONCLUSION: The best harvesting time of R. gmelini is early July.