Utricularia

Whitewoods introduces the plant genus Utricularia.

Tropospheric ozone and cadmium do not have interactive effects on growth, photosynthesis and mineral nutrients of Catalpa ovata seedlings in the urban areas of Northeast China

Heavy metal contamination and tropospheric ozone (O₃) pollution often co-occur in heavy industrial urban areas, adversely affecting urban plant health. Little is known about the characteristics of growth, physiological metabolism, bioaccumulation of cadmium (Cd) and mineral nutrients in urban trees under the combination of soil Cd contamination and elevated O₃ exposure. In this study, one-year-old street tree Catalpa ovata G. Don seedlings were exposed to Cd contaminated soil (0, 100, 500 mg/kg soil) with 40 µg/m³ O₃ (ambient air) and 120 µg/m³ O₃ (elevated O₃ exposure) for 4 weeks. The results revealed that 500 mg/kg soil Cd addition alone decreased net photosynthetic rate, stomatal conductance, peroxidase activity and increased abscisic acid content and oxidative injury in the leaves of C. ovata. Furthermore, Cd soil contamination decreased leaf, stem, root and total biomass and affected Cd, Mg, Fe, and Zn contents in leaves (P < 0.01), but it did not affect Mg, Fe and Zn contents in roots. O₃ exposure did not affect growth, net photosynthetic rate, Cd accumulation and mineral nutrient contents of C. ovata. No interactive effect between Cd and O₃ was found on growth, oxidative injury, photosynthetic rate, and the contents of Cd, Mg, Fe and Zn in plant tissues (P > 0.05). Our findings suggest that C. ovata is an appropriate tree species for urban greening and afforestation in heavy industrial urban areas with high O₃ pollution in Northeast China. To ensure successful afforestation in heavy industrial areas, the long-term and large scale studies are needed to advance our understanding of the combined effects from extreme climate conditions and multi-pollutant exposure on the metabolism of mature urban trees.

Effective pollination of Aeschynanthus acuminatus (Gesneriaceae) by generalist passerines, in sunbird-absent East Asia

Aeschynanthus (Gesneriaceae), a genus comprising approximately 160 species in subtropical Southeast Asia, has red, tubular flowers, typical of a sunbird pollination syndrome. A. acuminatus, the species that is distributed extending to the northern edge of the genus, where the specialized nectarivorous sunbirds are absent, possesses reddish-green flowers and a wide-open corolla tube, flowering time shifts from summer to winter and the species achieves high fruiting success. This atypical flower led us to investigate the pollination biology of this species. Three species of generalist passerines, Grey-cheeked Fulvetta (Alcippe morrisonia, Sylviidae), White-eared Sibia (Heterophasia auricularis, Leiothrichidae) and Taiwan Yuhina (Yuhina brunneiceps, Zosteropidae), were recorded visiting A. acuminatus flowers. Pollination effectiveness was quantified via conspecific pollen presence on stigmas and natural fruit set. The significantly high natural fruit set (60%) and conspecific pollen transfer rate (94%) indicate high reproductive success facilitated by the accurate pollen placement on the birds. The existence of copious (61 µL) and highly diluted (7%) hexose-dominant nectar, together with a major reflectance peak of corolla lobe in the long-wavelength red color spectrum, is consistent with the pollination syndrome of generalist passerines. The high pollination effectiveness of A. acuminatus due to the recruitment of generalist passerines as pollinators, and the specializations of floral traits to match generalist bird pollination, appear crucial in the successful colonization on islands such as Taiwan that lack specialized bird pollinators.

Pollination ecology of the Neotropical gesneriad Gloxinia perennis: chemical composition and temporal fluctuation of floral perfume

Although common among orchids, pollination by perfume-gathering male euglossine bees is quite rare in other Neotropical families. In Gesneriaceae, for example, it is reported in two genera only, Drymonia and Gloxinia. Flowers of G. perennis are known to emit perfume, thereby attracting male euglossine bees as pollinators. However, detailed reports on the pollination ecology, as well as on chemistry of floral perfume of individuals in natural populations, are still missing. In this study, we report on the pollination ecology of G. perennis, focusing on the ecological significance of its floral perfume. In natural populations in Peru, we documented the floral biology and breeding system of G. perennis, as well as its interaction with flower visitors. We also characterised the chemical composition of floral perfume, as well as its timing of emission. Gloxinia perennis is self-compatible and natural pollination success is high. Spontaneous self-pollination occurs as a 'just in case strategy' when pollinators are scarce. Perfume-collecting males of Eulaema cingulata and El. meriana were identified as pollinators. The perfume bouquet of G. perennis consists of 16 compounds. (E)-Carvone epoxide (41%) and limonene (23%) are the major constituents. Perfume emission is higher at 09:00 h, matching the activity peak of Eulaema pollinators. Flowers of G. perennis have evolved a mixed strategy to ensure pollination (i.e. self- and cross-pollination), but cross-pollination is favoured. The size and behaviour of Eulaema males enables only these bees to successfully cross-pollinate G. perennis. Furthermore, G. perennis floral perfume traits (i.e. chemistry and timing of emission) have evolved to optimise the attraction of these bees.

Regulation of flowering time via miR172-mediated APETALA2-like expression in ornamental gloxinia (Sinningia speciosa)

We investigated the microRNA172 (miR172)-mediated regulatory network for the perception of changes in external and endogenous signals to identify a universally applicable floral regulation system in ornamental plants, manipulation of which could be economically beneficial. Transgenic gloxinia plants, in which miR172 was either overexpressed or suppressed, were generated using Agrobacterium-mediated transformation. They were used to study the effect of altering the expression of this miRNA on time of flowering and to identify its mRNA target. Early or late flowering was observed in transgenic plants in which miR172 was overexpressed or suppressed, respectively. A full-length complementary DNA (cDNA) of gloxinia (Sinningia speciosa) APETALA2-like (SsAP2-like) was identified as a target of miR172. The altered expression levels of miR172 caused up- or down-regulation of SsAP2-like during flower development, which affected the time of flowering. Quantitative real-time reverse transcription PCR analysis of different gloxinia tissues revealed that the accumulation of SsAP2-like was negatively correlated with the expression of miR172a, whereas the expression pattern of miR172a was negatively correlated with that of miR156a. Our results suggest that transgenic manipulation of miR172 could be used as a universal strategy for regulating time of flowering in ornamental plants.

Genome-wide analysis of three histone marks and gene expression in Paulownia fortunei with phytoplasma infection

BACKGROUND

Paulownia withes'-broom (PaWB) disease caused by phytoplasma is a serious infectious disease for Paulownia. However, the underlying molecular pathogenesis is not fully understood. Recent studies have demonstrated that histone modifications could play a role in plant defense responses to pathogens. But there is still no available genome-wide histone modification data in non-model ligneous species infected with phytoplasma.

RESULTS

Here, we provided the first genome-wide profiles of three histone marks (H3K4me3, H3K36me3 and H3K9ac) in Paulownia fortunei under phytoplasma stress by using chromatin immunoprecipitation sequencing (ChIP-Seq). We found that H3K4me3, H3K36me3 and H3K9ac were mainly enriched in the genic regions in P. fortunei with (PFI) and without (PF) phytoplasma infection. ChIP-Seq analysis revealed 1738, 986, and 2577 genes were differentially modified by H3K4me3, H3K36me3 and H3K9ac marks in PFI under phytoplasma infection, respectively. The functional analysis of these genes suggested that most of them were mainly involved in metabolic pathways, biosynthesis of secondary metabolites, phenylpropanoid biosynthesis, plant-pathogen interaction and plant hormone signal transduction. In addition, the combinational analysis of ChIP-Seq and RNA-Seq showed that differential histone methylation and acetylation only affected a small subset of phytoplasma-responsive genes.

CONCLUSIONS

Taken together, this is the first report of integrated analysis of histone modifications and gene expression involved in Paulownia-phytoplasma interaction. Our results will provide the valuable resources for the mechanism studies of gene regulation in non-model plants upon pathogens attack.

Floral micromorphology of the bird-pollinated carnivorous plant species Utricularia menziesii R.Br. (Lentibulariaceae)

BACKGROUND AND AIMS

Bird pollination is rare among species in the genus Utricularia, and has evolved independently in two lineages of this genus. In Western Australia, the Western Spinebill, Acanthorhynchus superciliosus, visits flowers of Utricularia menziesii (section Pleiochasia: subgenus Polypompholyx). This study aimed to examine the micromorphology of U. menziesii flowers to assess traits that might be linked to its pollination strategy.

METHODS

Light microscopy, histochemistry and scanning electron microscopy were used. Nectar sugar composition was analysed using high-performance liquid chromatography.

KEY RESULTS

The flowers of U. menziesii fulfil many criteria that characterize bird-pollinated flowers: red colour, a large, tough nectary spur that can withstand contact with a hard beak, lack of visual nectar guides and fragrance. Trichomes at the palate and throat may act as tactile signals. Spur nectary trichomes did not form clearly visible patches, but were more frequently distributed along vascular bundles, and were small and sessile. Each trichome comprised a single basal cell, a unicellular short pedestal cell (barrier cell) and a multicelled head. These trichomes were much smaller than those of the U. vulgaris allies. Hexose-dominated nectar was detected in flower spurs. Fructose and glucose were present in equal quantities (43 ± 3.6 and 42 ± 3.6 g L-1). Sucrose was only detected in one sample, essentially at the limit of detection for the method used. This type of nectar is common in flowers pollinated by passerine perching birds.

CONCLUSIONS

The architecture of nectary trichomes in U. menziesii was similar to that of capitate trichomes of insect-pollinated species in this genus; thus, the most important specializations to bird pollination were flower colour (red), and both spur shape and size modification. Bird pollination is probably a recent innovation in the genus Utricularia, subgenus Polypompholyx, and is likely to have evolved from bee-pollinated ancestors.

Hunters or farmers? Microbiome characteristics help elucidate the diet composition in an aquatic carnivorous plant

BACKGROUND

Utricularia are rootless aquatic carnivorous plants which have recently attracted the attention of researchers due to the peculiarities of their miniaturized genomes. Here, we focus on a novel aspect of Utricularia ecophysiology-the interactions with and within the complex communities of microorganisms colonizing their traps and external surfaces.

RESULTS

Bacteria, fungi, algae, and protozoa inhabit the miniature ecosystem of the Utricularia trap lumen and are involved in the regeneration of nutrients from complex organic matter. By combining molecular methods, microscopy, and other approaches to assess the trap-associated microbial community structure, diversity, function, as well as the nutrient turn-over potential of bacterivory, we gained insight into the nutrient acquisition strategies of the Utricularia hosts.

CONCLUSIONS

We conclude that Utricularia traps can, in terms of their ecophysiological function, be compared to microbial cultivators or farms, which center around complex microbial consortia acting synergistically to convert complex organic matter, often of algal origin, into a source of utilizable nutrients for the plants.

Transcriptome reprogramming during severe dehydration contributes to physiological and metabolic changes in the resurrection plant Haberlea rhodopensis

BACKGROUND

Water shortage is a major factor that harms agriculture and ecosystems worldwide. Plants display various levels of tolerance to water deficit, but only resurrection plants can survive full desiccation of their vegetative tissues. Haberlea rhodopensis, an endemic plant of the Balkans, is one of the few resurrection plants found in Europe. We performed transcriptomic analyses of this species under slight, severe and full dehydration and recovery to investigate the dynamics of gene expression and associate them with existing physiological and metabolomics data.

RESULTS

De novo assembly yielded a total of 142,479 unigenes with an average sequence length of 1034 nt. Among them, 18,110 unigenes were differentially expressed. Hierarchical clustering of all differentially expressed genes resulted in seven clusters of dynamic expression patterns. The most significant expression changes, involving more than 15,000 genes, started at severe dehydration (~ 20% relative water content) and were partially maintained at full desiccation (< 10% relative water content). More than a hundred pathways were enriched and functionally organized in a GO/pathway network at the severe dehydration stage. Transcriptomic changes in key pathways were analyzed and discussed in relation to metabolic processes, signal transduction, quality control of protein and DNA repair in this plant during dehydration and rehydration.

CONCLUSION

Reprograming of the transcriptome occurs during severe dehydration, resulting in a profound alteration of metabolism toward alternative energy supply, hormone signal transduction, and prevention of DNA/protein damage under very low cellular water content, underlying the observed physiological and metabolic responses and the resurrection behavior of H. rhodopensis.

Evolution of ALOG gene family suggests various roles in establishing plant architecture of Torenia fournieri

BACKGROUND

ALOG (Arabidopsis LSH1 and Oryza G1) family with a conserved domain widely exists in plants. A handful of ALOG members have been functionally characterized, suggesting their roles as key developmental regulators. However, the evolutionary scenario of this gene family during the diversification of plant species remains largely unclear.

METHODS

Here, we isolated seven ALOG genes from Torenia fournieri and phylogenetically analyzed them with different ALOG members from representative plants in major taxonomic clades. We further examined their gene expression patterns by RT-PCR, and regarding the protein subcellular localization, we co-expressed the candidates with a nuclear marker. Finally, we explored the functional diversification of two ALOG members, TfALOG1 in euALOG1 and TfALOG2 in euALOG4 sub-clades by obtaining the transgenic T. fournieri plants.

RESULTS

The ALOG gene family can be divided into different lineages, indicating that extensive duplication events occurred within eudicots, grasses and bryophytes, respectively. In T. fournieri, seven TfALOG genes from four sub-clades exhibit distinct expression patterns. TfALOG1-6 YFP-fused proteins were accumulated in the nuclear region, while TfALOG7-YFP was localized both in nuclear and cytoplasm, suggesting potentially functional diversification. In the 35S:TfALOG1 transgenic lines, normal development of petal epidermal cells was disrupted, accompanied with changes in the expression of MIXTA-like genes. In 35S:TfALOG2 transgenic lines, the leaf mesophyll cells development was abnormal, favoring functional differences between the two homologous proteins. Unfortunately, we failed to observe any phenotypical changes in the TfALOG1 knock-out mutants, which might be due to functional redundancy as the case in Arabidopsis.

CONCLUSION

Our results unraveled the evolutionary history of ALOG gene family, supporting the idea that changes occurred in the cis regulatory and/or nonconserved coding regions of ALOG genes may result in new functions during the establishment of plant architecture.

Molecular Mechanisms Preventing Senescence in Response to Prolonged Darkness in a Desiccation-Tolerant Plant

The desiccation-tolerant plant Haberlea rhodopensis can withstand months of darkness without any visible senescence. Here, we investigated the molecular mechanisms of this adaptation to prolonged (30 d) darkness and subsequent return to light. H. rhodopensis plants remained green and viable throughout the dark treatment. Transcriptomic analysis revealed that darkness regulated several transcription factor (TF) genes. Stress- and autophagy-related TFs such as ERF8, HSFA2b, RD26, TGA1, and WRKY33 were up-regulated, while chloroplast- and flowering-related TFs such as ATH1, COL2, COL4, RL1, and PTAC7 were repressed. PHYTOCHROME INTERACTING FACTOR4, a negative regulator of photomorphogenesis and promoter of senescence, also was down-regulated. In response to darkness, most of the photosynthesis- and photorespiratory-related genes were strongly down-regulated, while genes related to autophagy were up-regulated. This occurred concomitant with the induction of SUCROSE NON-FERMENTING1-RELATED PROTEIN KINASES (SnRK1) signaling pathway genes, which regulate responses to stress-induced starvation and autophagy. Most of the genes associated with chlorophyll catabolism, which are induced by darkness in dark-senescing species, were either unregulated (PHEOPHORBIDE A OXYGENASE, PAO; RED CHLOROPHYLL CATABOLITE REDUCTASE, RCCR) or repressed (STAY GREEN-LIKE, PHEOPHYTINASE, and NON-YELLOW COLORING1). Metabolite profiling revealed increases in the levels of many amino acids in darkness, suggesting increased protein degradation. In darkness, levels of the chloroplastic lipids digalactosyldiacylglycerol, monogalactosyldiacylglycerol, phosphatidylglycerol, and sulfoquinovosyldiacylglycerol decreased, while those of storage triacylglycerols increased, suggesting degradation of chloroplast membrane lipids and their conversion to triacylglycerols for use as energy and carbon sources. Collectively, these data show a coordinated response to darkness, including repression of photosynthetic, photorespiratory, flowering, and chlorophyll catabolic genes, induction of autophagy and SnRK1 pathways, and metabolic reconfigurations that enable survival under prolonged darkness.

Delayed selfing ensures reproductive assurance in Utricularia praeterita and Utricularia babui in Western Ghats

Numerous bladderwort (Utricularia) species are distributed worldwide, but their reproductive biology is rarely investigated. Bladderworts are known to depend on tiny organisms to meet a significant proportion of their energy requirement by trapping them in bladders. However, information on the extent of their reliance on insects for pollination success is limited. We examined the reproductive strategy of two Utricularia species viz. Utricularia praeterita and U. babui, endemic to Western Ghats, India. The main aspects of the investigation involved floral biology, breeding system, pollination mechanism, and reproductive success. Flowers of both the species are structured for outbreeding through entomophilous floral suites, herkogamy, protandrous dichogamy and sensitive lobes of the stigma. With nearly 65% natural fruit-set, both the species appeared to be sufficiently open-pollinated. However, pollinators failed to show in plants of U. praeterita while in U. babui there was an apparent mismatch between the extent of fruit-set and pollinator visits. The study demonstrated that in the absence/insufficient visits of pollinators, the two species resort to autonomous selfing. In U. babui, denser patches of plants appeared to be crucial for attracting the pollinators. Both species are self-compatible, and reproductive success is predominantly achieved by delayed autonomous selfing. The sensitive stigma in the species fails to prevent selfing due to diminished herkogamy during the late anthetic stages. It is inferred that in the pollinator-limited environment, delayed selfing contributes to absolute natural fecundity in U. praeterita, while it produces a mixed progeny in U. babui.

Reproductive biology and pollination of the carnivorous Genlisea violacea (Lentibulariaceae)

Genlisea violacea is a Brazilian endemic carnivorous plant species distributed in the cerrado biome, mainly in humid environments, on sandy and oligotrophic soil or wet rocks. Studies on reproductive biology or pollination in the Lentibulariaceae are notably scarce; regarding the genus Genlisea, the current study is the first to show systematic and standardised research on reproductive biology from field studies to describe the foraging of visiting insects and determine the effective pollinators of Genlisea. We studied two populations of G. violacea through the observation of flower visitors for 4 months of the rainy and dry seasons. Stigmatic receptivity, pollen viability, and breeding system were evaluated together with histochemistry and morphological analyses of flowers. The flowers showed stigmatic receptivity of 100% in open buds and mature flowers, reducing to 80% for senescent flowers. Nearly 80% of pollen grains are viable, decreasing to 40-45% after 48 h. Nectar is produced by glandular trichomes inside the spur. Two bee species are effective pollinators: one of the genus Lasioglossum (subgenus Dialictus: Halictidae) and the other of the genus Ceratina (subgenus Ceratinula: family Apidae). Moreover, bee-like flies of the Syrphidae family may also be additional pollinators. Genlisea violacea is an allogamous and self-compatible species. The differences in flower-visiting fauna for both populations can be attributed to factors such as climate, anthropogenic effect, seasonal factors related to insects and plants, as well as the morphological variation of flowers in both populations.

Reproductive ecology of the carnivorous plant Pinguicula moranensis (Lentibulariaceae)

The interaction of plants with pollinators can be a determinant of their reproductive fitness. However, information about the pollination biology of carnivorous plants is scarce. To increase knowledge of reproductive ecology of carnivorous plants we focused on Pinguicula moranensis. Specifically, based on the presence of large, zygomorphic and spurred flowers, we predicted higher reproductive fitness in cross-pollinated than in self-pollinated flowers. Within a plot of 51 m² we characterised the reproductive phenology, including flower lifespan and stigmatic receptivity. We identified pollinators and their movement patterns within the plot. Breeding system was experimentally evaluated using hand-pollination (i.e. autonomous, self- and cross-pollination). Flowers of P. moranensis were visited by long-tongued pollinators, mainly members of the Lepidoptera. Hand-pollination experiments confirmed our prediction and suggest that flower traits might favour cross-pollination. We mainly discuss the implications of the patchy distribution of plants and behaviour of pollinators on gene movement in this plant species, as pollination between genetically related individuals could be occurring.

Genome-wide expression analysis of salt-stressed diploid and autotetraploid Paulownia tomentosa

Paulownia tomentosa is a fast-growing tree species with multiple uses. It is grown worldwide, but is native to China, where it is widely cultivated in saline regions. We previously confirmed that autotetraploid P. tomentosa plants are more stress-tolerant than the diploid plants. However, the molecular mechanism underlying P. tomentosa salinity tolerance has not been fully characterized. Using the complete Paulownia fortunei genome as a reference, we applied next-generation RNA-sequencing technology to analyze the effects of salt stress on diploid and autotetraploid P. tomentosa plants. We generated 175 million clean reads and identified 15,873 differentially expressed genes (DEGs) from four P. tomentosa libraries (two diploid and two autotetraploid). Functional annotations of the differentially expressed genes using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases revealed that plant hormone signal transduction and photosynthetic activities are vital for plant responses to high-salt conditions. We also identified several transcription factors, including members of the AP2/EREBP, bHLH, MYB, and NAC families. Quantitative real-time PCR analysis validated the expression patterns of eight differentially expressed genes. Our findings and the generated transcriptome data may help to accelerate the genetic improvement of cultivated P. tomentosa and other plant species for enhanced growth in saline soils.

Adaptive molecular evolution of the two-pore channel 1 gene TPC1 in the karst-adapted genus Primulina (Gesneriaceae)

BACKGROUND AND AIMS

Limestone karst areas possess high floral diversity and endemism. The genus Primulina, which contributes to the unique calcicole flora, has high species richness and exhibit specific soil-based habitat associations that are mainly distributed on calcareous karst soils. The adaptive molecular evolutionary mechanism of the genus to karst calcium-rich environments is still not well understood. The Ca²⁺-permeable channel TPC1 was used in this study to test whether its gene is involved in the local adaptation of Primulina to karst high-calcium soil environments.

METHODS

Specific amplification and sequencing primers were designed and used to amplify the full-length coding sequences of TPC1 from cDNA of 76 Primulina species. The sequence alignment without recombination and the corresponding reconstructed phylogeny tree were used in molecular evolutionary analyses at the nucleic acid level and amino acid level, respectively. Finally, the identified sites under positive selection were labelled on the predicted secondary structure of TPC1.

KEY RESULTS

Seventy-six full-length coding sequences of Primulina TPC1 were obtained. The length of the sequences varied between 2220 and 2286 bp and the insertion/deletion was located at the 5' end of the sequences. No signal of substitution saturation was detected in the sequences, while significant recombination breakpoints were detected. The molecular evolutionary analyses showed that TPC1 was dominated by purifying selection and the selective pressures were not significantly different among species lineages. However, significant signals of positive selection were detected at both TPC1 codon level and amino acid level, and five sites under positive selective pressure were identified by at least three different methods.

CONCLUSIONS

The Ca²⁺-permeable channel TPC1 may be involved in the local adaptation of Primulina to karst Ca²⁺-rich environments. Different species lineages suffered similar selective pressure associated with calcium in karst environments, and episodic diversifying selection at a few sites may play a major role in the molecular evolution of Primulina TPC1.

[Capture and selectivity of zooplankton by Utricularia foliosa (Lentibulariaceae) in the Ciénaga de Paredes, Santander, Colombia]

Utricularia is a genus of carnivorous plants that capture a wide range of aquatic organisms. Most of these plants grow in environments with nutrients deficiency and have the ability to change the conditions of their microenvironment. The aim of this research was to study the selectivity in the zooplankton capture by Utricularia foliosa in the Ciénaga de Paredes. Our study was undertaken between February and November, 2014. We tried to determine if there is selection in the plant’s food resources by the Czekanowski’s index, and the selection degree by the Savage and Ivlev’s indexes. Additionally, we studied the possible relationship between the patterns of zooplankton capture and selection, with physicochemical variables in the swamp. The Czekanowski’s index showed a food selection in plant resources throughout the flood pulse, with values between 0.28 and 0.41. We also found a significant positive selection with Savage's index for Lecane sp., Alona sp., Ceriodaphnia sp., and Bosmina sp. (p < 0.05); similar results were obtained with Ivlev’s index. The intensity in the selection of each captured genus varied significantly between hydrological periods and between high and low water levels in the swamp. It was possible to identify some changes in the ammonia and nitrate concentration and some variability in the electric conductivity of the swamp, which influenced the captures made by U. foliosa. This is the first paper that allows an approach to understand the selection of food resources for the species, using a selectivity index, and one of the few for the genus.

Resting electrical network activity in traps of the aquatic carnivorous plants of the genera Aldrovanda and Utricularia

In this study the MEA (multielectrode array) system was used to record electrical responses of intact and halved traps, and other trap-free tissues of two aquatic carnivorous plants, Aldrovanda vesiculosa and Utricularia reflexa. They exhibit rapid trap movements and their traps contain numerous glands. Spontaneous generation of spikes with quite uniform shape, propagating across the recording area, has been observed for all types of sample. In the analysis of the electrical network, higher richer synchronous activity was observed relative to other plant species and organs previously described in the literature: indeed, the time intervals between the synchronized clusters (the inter-spike intervals) create organized patterns and the propagation times vary non-linearly with the distance due to this synchronization. Interestingly, more complex electrical activity was found in traps than in trap-free organs, supporting the hypothesis that the nature of the electrical activity may reflect the anatomical and functional complexity of different organs. Finally, the electrical activity of functionally different traps of Aldrovanda (snapping traps) and Utricularia (suction traps) was compared and some differences in the features of signal propagation were found. According to these results, a possible use of the MEA system for the study of different trap closure mechanisms is proposed.

Potential for chromium (VI) bioremediation by the aquatic carnivorous plant Utricularia gibba L. (Lentibulariaceae)

The aquatic carnivorous plant Utricularia gibba has one of the smallest known genomes among flowering plants, and therefore, it is an excellent model organism for physiological and developmental studies. The main aim of our work was to check whether the ubiquitous U. gibba might be useful for the phytoremediation of the highly toxic and mobile hexavalent chromium in waters. Plants were incubated for 1 week in a 50 μM (2.6 mg dm(-3)) Cr(VI) solution in laboratory conditions. Our results revealed that the plant exhibits a very high accumulation capacity for Cr. The accumulation level was higher than 780 mg kg(-1) and a bioconcentration factor >300. On the other hand, the plants showed a low tolerance to the elevated Cr concentration, which was expressed in a significant decrease of the photosystem II activity. However, the most pronounced negative influence of chromate was found on the morphology and activity of the traps. Due to its high accumulation capacity, we suggest that U. gibba may be efficient in the removal of chromate over a short time scale. It can also provide a new molecular resource for studying the mechanisms of Cr(VI) detoxification.