Control of leaf development in the water fern Ceratopteris richardii by the auxin efflux transporter CrPINMa in the CRISPR/Cas9 analysis

BACKGROUND

PIN-FORMED genes (PINs) are crucial in plant development as they determine the directionality of auxin flow. They are present in almost all land plants and even in green algae. However, their role in fern development has not yet been determined. This study aims to investigate the function of CrPINMa in the quasi-model water fern Ceratopteris richardii.

RESULTS

CrPINMa possessed a long central hydrophilic loop and characteristic motifs within it, which indicated that it belonged to the canonical rather than the non-canonical PINs. CrPINMa was positioned in the lineage leading to Arabidopsis PIN6 but not that to its PIN1, and it had undergone numerous gene duplications. CRISPR/Cas9 genome editing had been performed in ferns for the first time, producing diverse mutations including local frameshifts for CrPINMa. Plants possessing disrupted CrPINMa exhibited retarded leaf emergence and reduced leaf size though they could survive and reproduce at the same time. CrPINMa transcripts were distributed in the shoot apical meristem, leaf primordia and their vasculature. Finally, CrPINMa proteins were localized to the plasma membrane rather than other cell parts.

CONCLUSIONS

CRISPR/Cas9 genome editing is feasible in ferns, and that PINs can play a role in fern leaf development.

Genomes tell tales of spores versus seeds

Genomes from ferns and a cycad reveal deep roots of plant reproduction.

A taxonomic and molecular survey of the pteridophytes of the Nectandra Cloud Forest Reserve, Costa Rica

Floristic surveys are crucial to the conservation of biodiversity, but the vast majority of such surveys are limited to listing species names, and few take into account the evolutionary history of species. Here, we combine classical taxonomic and molecular phylogenetic (DNA barcoding) approaches to catalog the biodiversity of pteridophytes (ferns and lycophytes) of the Nectandra Cloud Forest Reserve, Costa Rica. Surveys were carried out over three field seasons (2008, 2011, and 2013), resulting in 176 species representing 69 genera and 22 families of pteridophytes. Our literature survey of protected areas in Costa Rica shows that Nectandra has an exceptionally diverse pteridophyte flora for its size. Plastid rbcL was selected as a DNA barcode marker and obtained for >95% of pteridophyte taxa at this site. Combined molecular and morphological analyses revealed two previously undescribed taxa that appear to be of hybrid origin. The utility of rbcL for species identification was assessed by calculating minimum interspecific distances and found to have a failure rate of 18%. Finally we compared the distribution of minimum interspecific rbcL distances with two other areas that have been the focus of pteridophyte molecular surveys: Japan and Tahiti. The comparison shows that Nectandra is more similar to Japan than Tahiti, which may reflect the biogeographic history of these floras.

Simple and Divided Leaves in Ferns: Exploring the Genetic Basis for Leaf Morphology Differences in the Genus Elaphoglossum (Dryopteridaceae)

Despite the implications leaves have for life, their origin and development remain debated. Analyses across ferns and seed plants are fundamental to address the conservation or independent origins of megaphyllous leaf developmental mechanisms. Class I KNOX expression studies have been used to understand leaf development and, in ferns, have only been conducted in species with divided leaves. We performed expression analyses of the Class I KNOX and Histone H4 genes throughout the development of leaf primordia in two simple-leaved and one divided-leaved fern taxa. We found Class I KNOX are expressed (1) throughout young and early developing leaves of simple and divided-leaved ferns, (2) later into leaf development of divided-leaved species compared to simple-leaved species, and (3) at the leaf primordium apex and margins. H4 expression is similar in young leaf primordia of simple and divided leaves. Persistent Class I KNOX expression at the margins of divided leaf primordia compared with simple leaf primordia indicates that temporal and spatial patterns of Class I KNOX expression correlate with different fern leaf morphologies. However, our results also indicate that Class I KNOX expression alone is not sufficient to promote divided leaf development in ferns. Class I KNOX patterns of expression in fern leaves support the conservation of an independently recruited developmental mechanism for leaf dissection in megaphylls, the shoot-like nature of fern leaves compared with seed plant leaves, and the critical role marginal meristems play in fern leaf development.

Symplasmic Isolation Contributes to Somatic Embryo Induction and Development in the Tree Fern Cyathea delgadii Sternb

In this report, we describe studies on symplasmic communication and cellular rearrangement during direct somatic embryogenesis (SE) in the tree fern Cyathea delgadii. We analyzed changes in the symplasmic transport of low-molecular-weight fluorochromes, such as 8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt (HPTS) and fluorescein (delivered to cells as fluorescein diacetate, FDA), within stipe explants and somatic embryos originating from single epidermal cells and developing during 16-d long culture. Induction of SE is preceded by a restriction in fluorochrome distribution between certain explant cells. Microscopic analysis showed a series of cellular changes like a decrease in vacuole size, increase in vacuole numbers, and increased density of cytoplasm and deposition of electron-dense material in cell walls that may be related with embryogenic transition. In somatic embryos, the limited symplasmic communication between cells was observed first in linear tri-cellular embryos. Further development of the fern embryo was associated with the formation of symplasmic domains corresponding to the four segments of the plant body. Using symplasmic tracers, we provided evidence that the changes in plasmodesmata permeability are corelated with somatic-to-embryogenic transition and somatic embryo development.

Physical space interacts with clonal fragmentation and nutrient availability to affect the growth of Salvinia natans

Physical space, clonal fragmentation and nutrient availability can each affect the growth of clonal plants, but their interactive effect has been little studied. We grew un-fragmented (connected) and fragmented (disconnected) ramet pairs of the floating, clonal plant Salvinia natans in cylindrical containers with different diameters and heights (volumes) filled with solutions of two nutrient levels (high vs. low). To simulate competition environments that are commonly confronted by S. natans, we also added two ramets of another floating plants Spirodela polyrrhiza in each container. Biomass (total biomass, floating biomass and submerged biomass) and number of ramets of S. salvinia were higher in the containers with a larger diameter. Compared to the low nutrient level, the high nutrient level increased number of ramets, and altered submerged to floating mass ratio of S. salvinia. The impacts of physical space on floating mass and number of ramets were stronger under the high than under the low nutrient level. Clonal fragmentation positively affected biomass in the containers with a smaller volume (a smaller height and diameter), but had little impact in the containers with a larger volume (a larger height or diameter). Our results suggest that physical space can interact with nutrients and clonal fragmentation to affect the performance of S. salvinia under competition.

Variability of fatty acid profiles in ferns: Relation to fern taxonomy and seasonal development

Ferns are known to contain long chain polyunsaturated fatty acids which may provide health benefits. The objective of this study was to investigate ferns of Pacific temperate regions (Far East of Russia and New Zealand) as sources of valuable fatty acids: arachidonic (20:4n-6) and eicosapentaenoic (20:5n-3). Fatty acids were analyzed in fronds of 23 fern species from 12 families. Major fatty acids include: 18:3n-3 (6-68% of total fatty acids), 16:0 (6-33%), 18:2n-6 (5-46%), 18:1n-9 (1-60%), 20:4n-6 (1-16%). Polyunsaturated fatty acids of fern fronds belong to the omega-6 (16:2n-6, 18:2n-6, 18:3n-6, 20:2n-6, 20:3n-6, 20:4n-6) and omega-3 (16:3n-3, 18:3n-3, 18:4n-3, 20:3n-3, 20:4n-3, 20:5n-3) families. For the first time, Δ5-unsaturated polymethylene-interrupted fatty acids were reported for ferns: sciadonic (5,11,14-20:3) and juniperonic (5,11,14,17-20:4) acids (up to 1.9% and 0.4%, respectively). Fatty acid profiles in fern fronds were unrelated to fern taxonomy, but affected by spore presence: fronds with sporangia/spores contained more 18:1n-9 and/or 18:2n-6. The absolute content of 20:4n-6 was found to be relatively constant for a species in different seasons. 20:5n-3 was a minor fatty acid (traces-5%) which accumulates during the vegetation period. Young fronds of the New Zealand ferns Phymatosorus pustulatus and Pteridium esculentum were enriched in 20:4n-6, while aged fronds of Cyathea dealbata had the highest level of 20:5n-3. The mature fronds of the Far Eastern ferns Phegopteris connectilis, Dryopteris expansa, and Athyrium sinense were also enriched in 20:5n-3.

Fluctuations in cell cycle, morphology and metabolism of Anemia phyllitidis gametophytes are the most important hallmarks of GA3-induced antheridiogenesis

The research object concerns partially explained mechanisms of plant hormone participation in male sex determination in plants, among them in A. phyllitidis gametophytes during GA₃-induced antheridiogenesis. To provide an explanation of the mechanisms of fluorescence and white-light microscopy, cytophotometric, autoradiographic and spectrophotometic methods were used to study cell cycle, the number of nucleoli, the amount of DiOC₆-stained IMN/ER, in which endoplasmic reticulum (ER) constitutes the main part, and its distribution as well as the amounts of proteins and chlorophylls and activities of acidic (Ac) and basic (Ba) phosphatases (Phases). It was revealed that antheridiogenesis was accompanied by cell cycle arrest at S-phase, changes of the number of nucleoli with simultaneous changes of the amount of IMN/ER and its distribution as well as fluctuations of protein amounts and of activities of acidic (Ac) and basic (Ba) phosphatases (Phases). The results indicated that initiation of antheridiogenesis in A. phyllitidis gametophytes by GA₃ was related to the elevation of GAs/ANs in the culture media, during its induction phase, and the elevation of IMN/ER and GAs/ANs amounts, during expression phase of this process.

Key innovations in transition from homospory to heterospory

Heterospory (i.e. dimorphic spores) is a long-lasting topic discussed in plant biology. It is observed in many of ferns, fern allies, and seed plants. The rise of heterospory and the mechanisms underlying its success in plant evolution are not clearly elucidated. In this short communication, an attempt is made to shed some light on these two questions.

Separate and combined effects of glyphosate and copper on growth and antioxidative enzymes in Salvinia natans (L.) All

The coexistence of glyphosate and copper is widely found in bodies of water and terrestrial ecosystems due to widespread application of herbicides and heavy metal. However, their joint ecotoxicological risks in aquatic environments remain unknown. The experiment investigated the individual and combined effects of glyphosate and copper on the growth and physiological response in Salvinia natans (L.) All. The results showed that their joint toxicity is related to concentration. Antagonistic effects were induced when plants were exposed to low concentrations of glyphosate and copper (≤1 + 0.2 mg l-1). Synergistic effects were elicited at higher doses (≥5 + 1 mg l-1). In addition, increased hydrogen peroxide levels indicated the occurrence of oxidative stress at individual or combined exposures. To cope with oxidative stress, S. natans can activate the antioxidant defense systems, including increased superoxide dismutase and changes in peroxidase, ascorbate peroxidase and catalase. High concentrations of combined pollution exceed the oxidative defense capabilities of plants, and therefore, malondialdehyde content increased significantly. Our results indicated that the ecotoxicity of glyphosate or copper may be exacerbated in aquatic environments and caused obvious damage to S. natans.

Can fern spores develop hydration memory in response to priming?

Fern spores and seeds initiate germination with fast water uptake, followed by a stationary phase with no appreciable water uptake and biochemical and metabolic processes that precede germination. After that, seed, germination is avoided by dehydration, as part of the priming treatments. After dehydration, seeds maintain their metabolic advances (hydration memory). As a result, rehydrated seeds germinate rapidly. We hypothesized that, as seeds, fern spores may be capable of developing hydration memory. To assess priming, spores of six fern species were exposed to: four or eight days of hydration in water (hydro-priming) or in a soil matrix (matrix-priming); or 1 month of hydration in the soil of the collection site (natural-priming). At the end of the treatments, the spores were dehydrated in the dark and germinated under laboratory conditions. Germination was evaluated using lag-time, germination rate and germination percentage. Priming treatments shortened lag time and/or increased germination rate or germination percentage in relation to the controls. Matrix-priming (8 days) reduced the spore germination percentage in three species. Our results provide evidence that fern spores possess a hydration memory that probably evolved in the soil bank and suggests that hydration-dehydration cycles within the natural soil might provide advantages for successful germination.

Germination fitness of two temperate epiphytic ferns shifts under increasing temperatures and forest fragmentation

Ferns are an important component of ecosystems around the world. Studies of the impacts that global changes may have on ferns are scarce, yet emerging studies indicate that some species may be particularly sensitive to climate change. The lack of research in this subject is much more aggravated in the case of epiphytes, and especially those that live under temperate climates. A mathematical model was developed for two temperate epiphytic ferns in order to predict potential impacts on spore germination kinetics, in response to different scenarios of global change, coming from increasing temperature and forest fragmentation. Our results show that an increasing temperature will have a negative impact over the populations of these temperate epiphytic ferns. Under unfragmented forests the germination percentage was comparatively less influenced than in fragmented patches. This study highlight that, in the long term, populations of the studied epiphytic temperate ferns may decline due to climate change. Overall, epiphytic fern communities will suffer changes in diversity, richness and dominance. Our study draws attention to the role of ferns in epiphytic communities of temperate forests, emphasizing the importance of considering these plants in any conservation strategy, specifically forest conservation. From a methodological point of view, the model we propose could be easily used to dynamically monitor the status of ecosystems, allowing the quick prediction of possible future scenarios, which is a crucial issue in biodiversity conservation decision-making.

Are rates of species diversification and body size evolution coupled in the ferns?

PREMISE OF THE STUDY

Understanding the relationship between phenotypic evolution and lineage diversification is a central goal of evolutionary biology. To extend our understanding of the role morphological evolution plays in the diversification of plants, we examined the relationship between leaf size evolution and lineage diversification across ferns.

METHODS

We tested for an association between body size evolution and lineage diversification using a comparative phylogenetic approach that combined a time-calibrated phylogeny and leaf size data set for 2654 fern species. Rates of leaf size change and lineage diversification were estimated using BAMM, and rate correlations were performed for rates obtained for all families and individual species. Rates and patterns of rate-rate correlation were also analyzed separately for terrestrial and epiphytic taxa.

KEY RESULTS

We find no significant correlation between rates of leaf area change and lineage diversification, nor was there a difference in this pattern when growth habit is considered. Our results are consistent with the findings of an earlier study that reported decoupled rates of body size evolution and diversification in the Polypodiaceae, but conflict with a recent study that reported a positive correlation between body size evolution and lineage diversification rates in the tree fern family Cyatheaceae.

CONCLUSIONS

Our findings indicate that lineage diversification in ferns is largely decoupled from shifts in body size, in contrast to several other groups of organisms. Speciation in ferns appears to be primarily driven by hybridization and isolation along elevational gradients, rather than adaptive radiations featuring prominent morphological restructuring. The exceptional diversity of leaf morphologies in ferns appears to reflect a combination of ecophysiological constraints and adaptations that are not key innovations.

Responses of the nitrogen-fixing aquatic fern Azolla to water contaminated with ciprofloxacin: Impacts on biofertilization

We investigated the ability of the aquatic fern Azolla to take up ciprofloxacin (Cipro), as well as the effects of that antibiotic on the N-fixing process in plants grown in medium deprived (-N) or provided (+N) with nitrogen (N). Azolla was seen to accumulate Cipro at concentrations greater than 160 μg g^-1 dry weight when cultivated in 3.05 mg Cipro l^-1, indicating it as a candidate for Cipro recovery from water. Although Cipro was not seen to interfere with the heterocyst/vegetative cell ratios, the antibiotic promoted changes with carbon and nitrogen metabolism in plants. Decreased photosynthesis and nitrogenase activity, and altered plant's amino acid profile, with decreases in cell N concentrations, were observed. The removal of N from the growth medium accentuated the deleterious effects of Cipro, resulting in lower photosynthesis, N-fixation, and assimilation rates, and increased hydrogen peroxide accumulation. Our results shown that Cipro may constrain the use of Azolla as a biofertilizer species due to its interference with nitrogen fixation processes.

Is there foul play in the leaf pocket? The metagenome of floating fern Azolla reveals endophytes that do not fix N2 but may denitrify

Dinitrogen fixation by Nostoc azollae residing in specialized leaf pockets supports prolific growth of the floating fern Azolla filiculoides. To evaluate contributions by further microorganisms, the A. filiculoides microbiome and nitrogen metabolism in bacteria persistently associated with Azolla ferns were characterized. A metagenomic approach was taken complemented by detection of N₂ O released and nitrogen isotope determinations of fern biomass. Ribosomal RNA genes in sequenced DNA of natural ferns, their enriched leaf pockets and water filtrate from the surrounding ditch established that bacteria of A. filiculoides differed entirely from surrounding water and revealed species of the order Rhizobiales. Analyses of seven cultivated Azolla species confirmed persistent association with Rhizobiales. Two distinct nearly full-length Rhizobiales genomes were identified in leaf-pocket-enriched samples from ditch grown A. filiculoides. Their annotation revealed genes for denitrification but not N₂ -fixation. ¹⁵ N₂ incorporation was active in ferns with N. azollae but not in ferns without. N₂ O was not detectably released from surface-sterilized ferns with the Rhizobiales. N₂ -fixing N. azollae, we conclude, dominated the microbiome of Azolla ferns. The persistent but less abundant heterotrophic Rhizobiales bacteria possibly contributed to lowering O₂ levels in leaf pockets but did not release detectable amounts of the strong greenhouse gas N₂ O.

Is there foul play in the leaf pocket? The metagenome of floating fern Azolla reveals endophytes that do not fix N2 but may denitrify

Dinitrogen fixation by Nostoc azollae residing in specialized leaf pockets supports prolific growth of the floating fern Azolla filiculoides. To evaluate contributions by further microorganisms, the A. filiculoides microbiome and nitrogen metabolism in bacteria persistently associated with Azolla ferns were characterized. A metagenomic approach was taken complemented by detection of N₂ O released and nitrogen isotope determinations of fern biomass. Ribosomal RNA genes in sequenced DNA of natural ferns, their enriched leaf pockets and water filtrate from the surrounding ditch established that bacteria of A. filiculoides differed entirely from surrounding water and revealed species of the order Rhizobiales. Analyses of seven cultivated Azolla species confirmed persistent association with Rhizobiales. Two distinct nearly full-length Rhizobiales genomes were identified in leaf-pocket-enriched samples from ditch grown A. filiculoides. Their annotation revealed genes for denitrification but not N₂ -fixation. ¹⁵ N₂ incorporation was active in ferns with N. azollae but not in ferns without. N₂ O was not detectably released from surface-sterilized ferns with the Rhizobiales. N₂ -fixing N. azollae, we conclude, dominated the microbiome of Azolla ferns. The persistent but less abundant heterotrophic Rhizobiales bacteria possibly contributed to lowering O₂ levels in leaf pockets but did not release detectable amounts of the strong greenhouse gas N₂ O.

Urea application promotes amino acid metabolism and membrane lipid peroxidation in Azolla

A pot experiment was conducted to evaluate the effect of urea on nitrogen metabolism and membrane lipid peroxidation in Azolla pinnata. Compared to controls, the application of urea to A. pinnata resulted in a 44% decrease in nitrogenase activity, no significant change in glutamine synthetase activity, 660% higher glutamic-pyruvic transaminase, 39% increase in free amino acid levels, 22% increase in malondialdehyde levels, 21% increase in Na⁺/K⁺- levels, 16% increase in Ca²⁺/Mg²⁺-ATPase levels, and 11% decrease in superoxide dismutase activity. In terms of H₂O₂ detoxifying enzymes, peroxidase activity did not change and catalase activity increased by 64% in urea-treated A. pinnata. These findings suggest that urea application promotes amino acid metabolism and membrane lipid peroxidation in A. pinnata.

Fern Stomatal Responses to ABA and CO2 Depend on Species and Growth Conditions

Changing atmospheric CO₂ levels, climate, and air humidity affect plant gas exchange that is controlled by stomata, small pores on plant leaves and stems formed by guard cells. Evolution has shaped the morphology and regulatory mechanisms governing stomatal movements to correspond to the needs of various land plant groups over the past 400 million years. Stomata close in response to the plant hormone abscisic acid (ABA), elevated CO₂ concentration, and reduced air humidity. Whether the active regulatory mechanisms that control stomatal closure in response to these stimuli are present already in mosses, the oldest plant group with stomata, or were acquired more recently in angiosperms remains controversial. It has been suggested that the stomata of the basal vascular plants, such as ferns and lycophytes, close solely hydropassively. On the other hand, active stomatal closure in response to ABA and CO₂ was found in several moss, lycophyte, and fern species. Here, we show that the stomata of two temperate fern species respond to ABA and CO₂ and that an active mechanism of stomatal regulation in response to reduced air humidity is present in some ferns. Importantly, fern stomatal responses depend on growth conditions. The data indicate that the stomatal behavior of ferns is more complex than anticipated before, and active stomatal regulation is present in some ferns and has possibly been lost in others. Further analysis that takes into account fern species, life history, evolutionary age, and growth conditions is required to gain insight into the evolution of land plant stomatal responses.

Non-linear growth in tree ferns, Dicksonia antarctica and Cyathea australis

Tree ferns are an important structural component of forests in many countries. However, because their regeneration is often unrelated to major disturbances, their age is often difficult to determine. In addition, rates of growth may not be uniform, which further complicates attempts to determine their age. In this study, we measured 5 years of growth of Cyathea australis and Dicksonia antarctica after a large wildfire in 2009 in south-eastern Australia. We found growth rates of these two species were unaffected by aspect and elevation but slope had a minor effect with D. antarctica growing 0.3mm faster for each additional degree of slope. Geographic location influenced growth in both species by up to 12 - 14mm/yr. The most consistent factor influencing growth rate, however, was initial height at the time of the 2009 fire; a finding consistent in both species and all geographic locations. For both tree fern species, individuals that were taller at the commencement of the study had greater overall growth for the duration of the study. This effect did not decrease even among the tallest tree ferns in our study (up to 6 metres tall). Overall, Cyathea australis averaged 73 (± 22)mm/year of growth (± 1SD), with the rate increasing 5mm/yr per metre of additional height. Dicksonia antarctica averaged 33 (± 13)mm/year, increasing by 6mm/yr/m. Growth rates dependent on initial height were unexpected and we discuss possible reasons for this finding. Variable growth rates also suggest that common age estimation methods of dividing height by average growth rate are likely to underestimate the age of short tree ferns, while overestimating the age of tall tree ferns, particularly if they have been subject to a fire.

Habitat filtering and exclusion of weak competitors jointly explain fern species assemblage along a light and water gradient

Fern species are an important component of the diversity of forest plant communities, but very little is known about how fern communities assemble in different environments. In this study, we use multiple trait-based tests to examine the relationships between several key eco-physiological traits which are direct indicators of shade and drought tolerance, and the abundance of fern species in pine forest (PF), pine and mixed broad leaf forest (PMBF) and matured broad leaf forest (MBF) in southern China. These forests are characterized by decreasing light but increasing water availability during succession, and the fern communities correspondingly differ in species composition. We tested community assembly using functional trait distributions and found that habitat filtering and exclusion of weak competitive traits among coexisting species jointly explain fern shade tolerance as measured by photosynthetic capacity (PR), photosynthetic nutrient efficiency (PNUE and PPUE) and water use efficiency as measured by carbon isotope ratio (CIR), and constitute important determinants of fern community assembly in all three forests. These observed fern plant strategies are consistent with known responses of other plant taxa such as flowering plants in similar successional environments and illustrate the value of functional trait based analyses to study community assembly.

From phytoaccumulation to post-harvest use of water fern for landfill management

We examined the potential of Azolla japonica as a remediating plant for leachate channels and post-accumulation use as fertilizer for landfill slope. The harvested biomass of Azolla after one month grown in leachate was 254% that of the initial biomass and the predicted annual harvestable biomass of Azolla using a growth model was 32 times that of the initial biomass. Na, Fe, Mn, Mg, and P were accumulated in Azolla at very high concentrations. Such rapid increase of biomass and high accumulation rates suggest that this plant could be an excellent remediating plant. The post-harvest use of Azolla as compost was studied for the management and use of phytoaccumulating Azolla. Metal contents of Azolla compost were below permissible limits for co-composting material. Nitrogen, organic matter, P, and Mg content of the Azolla compost improved the soil condition of the landfill and enhanced ecophysiological responses of the plants. The application of Azolla compost can improve management of sanitary landfills, including the restoration of vegetation. Considering its ease of harvesting, high accumulation rates, harvestable biomass and suitability for composting, Azolla can provide a suitable solution for sustainable management of leachate channels and landfill slopes.

Competition between Free-Floating Plants Is Strongly Driven by Previously Experienced Phosphorus Concentrations in the Water Column

Nutrients can determine the outcome of the competition between different floating plant species. The response of floating plants to current phosphorus levels may be affected by previously experienced phosphorus concentrations because some species have the ability to store excess phosphorus for later use. This might have an impact on their competition. Here, we investigate the effect of previous and actual phosphorus concentrations on the growth rate of free-floating plant species (Azolla filiculoides, Lemna minor/gibba and Ricciocarpus natans)and the effect of phosphorus history on the competition between L. minor/gibba and A. filiculoides and between L. minor/gibba and R. natans. As expected, plant growth was lower when previously kept at low instead of high phosphorus concentrations. Growth of L. minor/gibba and A. filiculoides with a phosphorus rich history was comparable for low and high actual phosphorus concentrations, however, internal phosphorus concentrations were significantly lower with low actual phosphorus concentration. This indicates that both species perform luxury phosphorus uptake. Furthermore, internal P concentration in Azolla and Lemna increased within two weeks after a period of P deficit without a strong increase in growth. A. filiculoides in a mixture with L. minor/gibba grew faster than its monoculture. Morphological differences may explain why A. filiculoides outcompeted L. minor/gibba and these differences may be induced by phosphorus concentrations in the past. Growth of L. minor/gibba was only reduced by the presence of A. filiculoides with a high phosphorus history. Growth of L. minor/gibba and R. natans in mixtures was positively affected only when they had a high phosphorus history themselves and their competitor a low phosphorus history. These observations clearly indicate that phosphorus history of competing plants is important for understanding the outcome of the competition. Therefore, actual and previously experienced phosphorus concentrations should be taken into account in future studies dealing with competition between plants.

The endocrine disruptor nonylphenol induces sublethal toxicity in vascular plant development at environmental concentrations: A risk for riparian plants and irrigated crops?

In recent years, there is a growing concern among the scientific community about the presence of the so-called emergent pollutants in waters of different countries, especially endocrine-disrupting compounds (EDCs) that have the ability to alter the hormonal system. One of the substances found almost ubiquitously and in higher concentrations is the alkylphenol nonylphenol. Albeit this compound is included in priority lists as a probable risk for human health and the environment, little is known about its effects on developing plants. The aim of this work is to assess the acute and sub-chronic toxicity of environmental concentrations of nonylphenol in riparian vascular plant development using spores of the fern Polystichum setiferum and a biomarker-based approach: mitochondrial activity (cell viability), chlorophyll (plant physiology) and DNA content (growth). Mitochondrial activity and DNA content show that nonylphenol induces acute and sub-chronic toxicity at 48 h and after 1 week, respectively. Significant effects are observed in both parameters in fern spores at ng L(-1) but chlorophyll autofluorescence shows little changes. The inhibition of germination by natural allelochemicals has been reported to be related with the active hydroxyl group of phenolic compounds and largely independent of the structural nucleus to which it is attached. Results presented in this study suggest that environmental concentrations of nonylphenol could interfere with higher plant germination development by mimicking natural allelochemicals and/or phytohormones acting as a "phytoendocrine disruptor" likely posing ecophysiological risks.

Aquatic microphylla Azolla: a perspective paradigm for sustainable agriculture, environment and global climate change

This review addresses the perspectives of Azolla as a multifaceted aquatic resource to ensure ecosystem sustainability. Nitrogen fixing potential of cyanobacterial symbiont varies between 30 and 60 kg N ha(-1) which designates Azolla as an important biological N source for agriculture and animal industry. Azolla exhibits high bioremediation potential for Cd, Cr, Cu, and Zn. Azolla mitigates greenhouse gas emission from agriculture. In flooded rice ecosystem, Azolla dual cropping decreased CH4 emission by 40 % than did urea alone and also stimulated CH4 oxidation. This review highlighted integrated approach using Azolla that offers enormous public health, environmental, and cost benefits.

Sensitivity of three tree ferns during their first phase of life to the variation of solar radiation and water availability in a Mexican cloud forest

PREMISE OF THE STUDY

Regeneration niche differentiation promotes species coexistence and diversity; however, the ecological implications for the initial life phases of the majority of pteridophytes are unknown. We analyzed the sensitivity of gametophytes and juvenile sporophytes of the tree ferns Alsophila firma, Cyathea divergens, and Lophosoria quadripinnata to variation in light and water availability.

METHODS

We evaluated gametophyte desiccation tolerance using saturated salt solutions and gametophyte solar radiation tolerance by direct exposure. We also transplanted juvenile sporophytes in environments with 7% and 23% canopy openness and two watering levels.

KEY RESULTS

The response of photosynthetic efficiency and water content suggest that the gametophytes of the three species require high relative humidity, tolerate direct solar radiation for up to 30 min and that the response is not species-dependent. Sporophyte size and gas exchange were greater in the more open site, but decreased watering had a lesser effect on these variables in the more closed site. Relative growth rate correlated with the net assimilation rate and leaf weight ratio. Juvenile sporophytes of A. firma were more shade tolerant, while those of C. divergens and L. quadripinnata acclimatized to both environments.

CONCLUSIONS

Specialization to humid habitats in the tree fern gametophyte restricts the species to humid forests, while differences in the plasticity of the sporophyte facilitate coexistence of the species.

Effects of the naturally-occurring contaminant microcystins on the Azolla filiculoides-Anabaena azollae symbiosis

Harmful algal blooms (HABs) contaminate aquatic ecosystems and are responsible for animal poisoning worldwide. We conducted a toxicity test with the aquatic fern and the biofertilizer, Azolla filiculoides. The sporophytes were exposed to three concentrations (0.01, 0.1 and 1μgmL(-1)) of a microcystin (MC) cyanobacterial crude extract and purified MC-LR. The growth of A. filiculoides decreased only at 1μgmL(-1) crude extract concentration while with MC-LR it decreased at all the tested concentrations, indicating that the presence of other compounds in the crude extract altered toxicity and stimulated the fern growth at lower concentrations (0.01 and 0.1μgmL(-1)). Both phycoerythrocyanin and allophycocyanin levels decreased in all the concentrations of crude extract and MC-LR. The phycocyanin had a marked increase at 0.1μgmL(-1) crude extract concentration and a marked decrease at 1μgmL(-1) MC-LR concentration. These changes in the phycobiliprotein content indicate a shift in the antenna pigments of the cyanobionts of A. filiculoides. The changes in two oxidative stress enzymes, glutathione reductase for the crude extract assay and glutathione peroxidase for MC-LR assay, points towards the induction of stress defense responses. The low bioconcentration factor in both crude extract and MC-LR treatments can suggest the low uptake of microcystins, and indicates that the aquatic fern can be used as a biofertilizer and as animal feed but is not suitable for MC phytoremediation.

Higher clonal integration in the facultative epiphytic fern Selliguea griffithiana growing in the forest canopy compared with the forest understorey

BACKGROUND AND AIMS

The advantage of clonal integration (resource sharing between connected ramets of clonal plants) varies and a higher degree of integration is expected in more stressful and/or more heterogeneous habitats. Clonal facultative epiphytes occur in both forest canopies (epiphytic habitats) and forest understories (terrestrial habitats). Because environmental conditions, especially water and nutrients, are more stressful and heterogeneous in the canopy than in the understorey, this study hypothesizes that clonal integration is more important for facultative epiphytes in epiphytic habitats than in terrestrial habitats.

METHODS

In a field experiment, an examination was made of the effects of rhizome connection (connected vs. disconnected, i.e. with vs. without clonal integration) on survival and growth of single ramets, both young and old, of the facultative epiphytic rhizomatous fern Selliguea griffithiana (Polypodiaceae) in both epiphytic and terrestrial habitats. In another field experiment, the effects of rhizome connection on performance of ramets were tested in small (10 × 10 cm(2)) and large (20 × 20 cm(2)) plots in both epiphytic and terrestrial habitats.

KEY RESULTS

Rhizome disconnection significantly decreased survival and growth of S. griffithiana in both experiments. The effects of rhizome disconnection on survival of single ramets and on ramet number and growth in plots were greater in epiphytic habitats than in terrestrial habitats.

CONCLUSIONS

Clonal integration contributes greatly to performance of facultative epiphytic ferns, and the effects were more important in forest canopies than in forest understories. The results therefore support the hypothesis that natural selection favours genotypes with a higher degree of integration in more stressful and heterogeneous environments.

[Investigation on resource and quality assessment of Cibotii Rhizoma]

The study is aimed to understand the resource and the current situation of the use of Cibotii Rhizoma and provide the basis for protecting and utilization. The method of literature survey, field survey and quality assessment were applied in the study. The results showed that all the Cibotii Rhizoma came from wild resource and was mainly founded in Fujian, Guangxi, Guizhou, Yunnan, Guangdong, Hunan, Jiangxi, Sichuan, Chongqing, Zhejiang, etc. It contains over 5 000 000 kg in the area which total is about 7 000 hm2. The annual output is over 850 000 kg. At present, there is no cultivated resources. Based on the investigation and market sampling analysis from various regions, the results showed that the quality of the collected crude drugs conformed with the regulations of the Chinese pharmacopoeia. However the qualification rate of decoction pieces of Cibotii Rhizoma in market was only 56.4%. At present, the resource of Cibotii Rhizoma could meet the needs of medinal uses. It is important to protect the wild resource which is less and less because of the environmental factors. It also need to make a standard of processing method to ensure the safety, and solve quality problem of the decoction pieces.

Developmental morphology of the typical cordate gametophyte of a homosporous leptosporangiate fern, Lygodium japonicum (Lygodiaceae), focusing on the initial cell behavior of two distinct meristems

PREMISE OF THE STUDY

Understanding the origin and early evolution of vascular plants requires thorough consideration of the gametophyte generation of ferns and lycophytes. Unfortunately, information about this generation is quite limited. To reveal the origin and evolution of varied gametophyte shapes, we used comparative morphological studies of meristem behavior of gametophytes of Lygodium japonicum, which exhibit the typical cordate shape.

METHODS

Microscopic images of epi-illuminated growing gametophytes cultured from spores were captured periodically using a metallurgical microscope equipped with a digital camera to analyze the cell lineage in the meristem.

KEY RESULTS

Gametophytes form from two meristems: the apical-cell-based meristem and the multicellular meristem. The triangular apical cell produces six to eight derivatives from two lateral facets, then disappears. Subsequently, the multicellular meristem, with a row of several rectangular cells, forms in the notch. These rectangular cells divide asynchronously in the periclinal and anticlinal walls to produce cells to both lateral sides and downward. Usually two, and sometimes three, cells located at the center of the meristem divide at a slower pace in the periclinal and anticlinal planes than others at the periphery. The cells at the periphery are pushed away and become involved in the wing base.

CONCLUSIONS

The triangular apical cell behaves as a permanent initial cell. In the multicellular meristem, however, two or three central cells behave as initial cells that are transient and regulated in a position-dependent manner. The organization and behavior of both meristems are shared with the ribbon-shaped gametophytes of Colysis.

Gene silencing by DNA interference in fern gametophytes

RNA interference is commonly used for posttranscriptional silencing of target gene transcripts. In fern gametophytes, however, sequence-specific gene silencing is possible by introducing double-stranded DNA fragments into gametophyte cells by particle bombardment. Silencing could be transmitted all over the gametophyte through live cells. Further, inheritance of the gene silencing to the progeny is depending on the gene used. Here we describe how to introduce the DNA fragments into the gametophyte cells and how to screen the DNA-transferred cells.

Multiflagellated sperm cells of Ceratopteris richardii are bathed in arabinogalactan proteins throughout development

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PREMISE OF THE STUDY

Sperm cell differentiation in ferns involves the origin of an elaborate locomotory apparatus, including 70+ flagella, and the structural modification of every cellular component. Because arabinogalactan proteins (AGPs) are implicated in molecular signaling and in regulation of plant development, we speculated that these glycoproteins would be present during spermiogenesis in ferns.•

METHODS

Using β-glucosyl Yariv reagents that specifically bind to and inhibit AGPs and immunogold localizations with monoclonal antibodies JIM13, JIM8, and LM6, we examined the specific expression patterns of AGPs and inhibited their function during sperm cell development in the model fern Ceratopteris richardii.•

KEY RESULTS

Developing sperm cells stained intensely with Yariv phenylglycosides, demonstrating the presence of AGPs. JIM13-AGP epitopes were widespread throughout development in the expanding extraprotoplasmic matrix (EPM) in which flagella elongate, cytoplasm is eliminated, and spherical spermatids become coiled. JIM8 and LM6 epitopes localized to the plasmalemma on growing flagella and on the rapidly changing sperm cell body. Spermatids treated with β-glucosyl lacked an EPM and formed fewer, randomly arranged flagella.•

CONCLUSIONS

We demonstrated that AGPs are abundant in the EPM and along the plasmalemma and that the three AGP epitopes have specific expression patterns during development. Coupled with inhibition studies, these results identify AGPs as critical to the formation of an extraprotoplasmic matrix and the consequent origin and development of flagella in an orderly and precise fashion around the cell. We speculate that AGPs may play additional roles as signaling molecules involved in cell shaping, cytoskeletal development, vesicle trafficking, and cytoplasmic elimination.

Are fern stomatal responses to different stimuli coordinated? Testing responses to light, vapor pressure deficit, and CO2 for diverse species grown under contrasting irradiances

The stomatal behavior of ferns provides an excellent system for disentangling responses to different environmental signals, which balance carbon gain against water loss. Here, we measured responses of stomatal conductance (gs ) to irradiance, CO2 , and vapor pressure deficit (VPD) for 13 phylogenetically diverse species native to open and shaded habitats, grown under high- and low-irradiance treatments. We tested two main hypotheses: that plants adapted and grown in high-irradiance environments would have greater responsiveness to all stimuli given higher flux rates; and that species' responsiveness to different factors would be correlated because of the relative simplicity of fern stomatal control. We found that species with higher light-saturated gs had larger responses, and that plants grown under high irradiance were more responsive to all stimuli. Open habitat species showed greater responsiveness to irradiance and CO2 , but lower responsiveness to VPD; a case of plasticity and adaptation tending in different directions. Responses of gs to irradiance and VPD were positively correlated across species, but CO2 responses were independent and highly variable. The novel finding of correlations among stomatal responses to different stimuli suggests coordination of hydraulic and photosynthetic signaling networks modulating fern stomatal responses, which show distinct optimization at growth and evolutionary time-scales.

A simple technique for tracking individual spore and gametophyte development in Adiantum lunulatum Burm. f. using modified extra thin alginate film technique

A new technique was developed for accurate calculation of percent germination and tracking of individual spores from germination to gametophyte development in Adiantum lunulatum. High percentage of ETAF immobilized spore germination (72.4%) was followed by development of gametophytic clumps. The ETAF immobilized clumps were cut into pieces and multiplied en masse. Apomictic sporophytes developed from the gametophytes. This indicated the potential of ETAF for mass propagation of A. lunulatum without the need to start from spores. Since individual spores can be tracked from germination to gametophyte development, the ETAF technique has the potential to be used for (i) harvesting uniformly developed plants of similar age for extensive experimentations and commercial utilization and (ii) detailed study on developmental and reproductive biology of different ferns and fern allies.

Azolla domestication towards a biobased economy?

Due to its phenomenal growth requiring neither nitrogen fertilizer nor arable land and its biomass composition, the mosquito fern Azolla is a candidate crop to yield food, fuels and chemicals sustainably. To advance Azolla domestication, we research its dissemination, storage and transcriptome. Methods for dissemination, cross-fertilization and cryopreservation of the symbiosis Azolla filiculoides-Nostoc azollae are tested based on the fern spores. To study molecular processes in Azolla including spore induction, a database of 37 649 unigenes from RNAseq of microsporocarps, megasporocarps and sporophytes was assembled, then validated. Spores obtained year-round germinated in vitro within 26 d. In vitro fertilization rates reached 25%. Cryopreservation permitted storage for at least 7 months. The unigene database entirely covered central metabolism and to a large degree covered cellular processes and regulatory networks. Analysis of genes engaged in transition to sexual reproduction revealed a FLOWERING LOCUS T-like protein in ferns with special features induced in sporulating Azolla fronds. Although domestication of a fern-cyanobacteria symbiosis may seem a daunting task, we conclude that the time is ripe and that results generated will serve to more widely access biochemicals in fern biomass for a biobased economy.

Impact of mycorrhization on the abundance, growth and leaf nutrient status of ferns along a tropical elevational gradient

Mycorrhizal fungi are crucial for the ecological success of land plants, providing their hosts with nutrients in exchange for organic C. However, not all plants are mycorrhizal, especially ferns, of which about one-third of the species lack this symbiosis. Because the mycorrhizal status is evolutionarily ancestral, this lack of mycorrhizae must have ecological advantages, but what these advantages are and how they affect the competitive ability of non-mycorrhizal plants under natural conditions is currently unknown. To address this uncertainty, we studied terrestrial fern assemblages and species abundances as well as their mycorrhization status, leaf nutrient concentration and relative annual growth along an elevational gradient in the Ecuadorian Andes (500-4,000 m). We surveyed the mycorrhizal status of 375 root samples belonging to 85 species, and found mycorrhizae in 89% of the samples. The degree of mycorrhization decreased with elevation but was unrelated to soil nutrients. Species with mycorrhizae were significantly more abundant than non-mycorrhizal species, but non-mycorrhizal species had significantly higher relative growth and concentrations of leaf N, P, Mg, and Ca. Our study thus shows that despite lower abundances, non-mycorrhizal fern species did not appear to be limited in their growth or nutrient supply relative to mycorrhizal ones. As a basis for future studies, we hypothesize that non-mycorrhizal fern species may be favoured in special microhabitats of the forest understory with high soil nutrient or water availability, or that the ecological benefit of mycorrhizae is not related to nutrient uptake but rather to, for example, pathogen resistance.

Healthy response from chromium survived pteridophytic plant-Ampelopteris prolifera with the interaction of mycorrhizal fungus-Glomus deserticola

Interaction between arbuscular mycorrhizal fungus Glomus deserticola and pteridophytic member Ampelopteris prolifera was found abundant on entire growth level based on elemental composition and gaseous exchange as a potential remediation system for phytoextraction of chromium. Inoculated A. prolifera (AM) and non-inoculated A. prolifera (Non-AM) were supplied with two Cr species: 12 mmol of trivalent cation (Cr(+3)) [Cr(III)] and 0.1 mmol of divalent dichromate anion (Cr2O7(-2)) [Cr(VI)]. Both Cr species were found to be depressed in overall growth and inefficient stomatal conductance (g(s)) and net photosynthesis (NP). Mycorrhizal association was found to be natural scavenger of Cr toxicity as indicated by greater growth in plants exposed to Cr species, and increased gas exchange of Cr(III) treated plants. Though, chromium reduction resulted lower level of nitrogen (N), phosphorus (P), and potassium (K) but interestingly elevated the level of aluminum (Al), iron (Fe), and zinc (Zn) uptake in many folds which is the significance of sustainable growth of plant.

Uptake and toxicity of arsenic, copper, and silicon in Azolla caroliniana and Lemna minor

Here we report on the analysis of two aquatic plant species, Azolla caroliniana and Lemna minor, with respect to tolerance and uptake of co-occurring arsenic, copper, and silicon for use in engineered wetlands. Plants were cultured in nutrient solution that was amended with arsenic (0 or 20 microM), copper (2 or 78 microM), and silicon (0 or 1.8 mM) either singly or in combination. We hypothesized that arsenic and copper would negatively affect the uptake of metals, growth, and pigmentation and that silicon would mitigate those stresses. Tolerance was assessed by measuring growth of biomass and concentrations of chlorophyll and anthocyanins. Both plant species accumulated arsenic, copper, and silicon; L. minor generally had higher levels on a per biomass basis. Arsenic negatively impacted A. caroliniana, causing a 30% decrease in biomass production and an increase in the concentration of anthocyanin. Copper negatively impacted L. minor, causing a 60% decrease in biomass production and a 45% decrease in chlorophyll content. Silicon augmented the impact of arsenic on biomass production in A. caroliniana but mitigated the effect of copper on L. minor. Our results suggest that mixtures of plant species may be needed to maximize uptake of multiple contaminants in engineered wetlands.

Structure and function of CrACA1, the major PM-type Ca2+-ATPase, expressed at the peak of the gravity-directed trans-cell calcium current in spores of the fern Ceratopteris richardii

Spores of the fern Ceratopteris richardii have proven to be a valuable single-cell system for studying gravity responses. The earliest cellular change directed by gravity in these cells is a trans-cell calcium current, which peaks near 10 h after the spores are induced to germinate. This current is needed for gravity-directed axis alignment, and its peak is coincident with the time period when gravity polarises the direction of subsequent nuclear migration and rhizoid growth. Transcriptomic analysis of genes expressed at the 10-h time point revealed several that encode proteins likely to be key components that either drive the current or regulate it. Notable among these is a plasma membrane (PM)-type Ca(2+) ATPase, CrACA1, whose activity pumping Ca(2+) out of cells is regulated by gravity. This report provides an initial characterisation of the structure and expression of this protein, and demonstrates its heterologous function complementing the K616 mutant of yeast, which is deficient in PM-type Ca(2+) pump activity. Gravity-induced changes in the trans-cell Ca(2+) current occur within seconds, a result consistent with the hypothesis that the force of gravity can rapidly alter the post-translational state of the channels and pumps that drive this current across spore cells. This report identifies a transporter likely to be a key driver of the current, CrACA1, and characterises the role of this protein in early germination and gravity-driven polarity fixation through analysis of expression levels, functional complementation and pharmacological treatments. These data, along with newly available transcriptomic data obtained at the 10-h time point, indicate that CrACA1 is present, functional and likely a major contributing component of the trans-cell Ca(2+) efflux. CrACA1 is not necessary for polar axis alignment, but pharmacological perturbations of it disrupt rhizoid development. These data support and help refine the post-translational modification model for gravity responses.

The simulation model of growth and cell divisions for the root apex with an apical cell in application to Azolla pinnata

In contrast to seed plants, the roots of most ferns have a single apical cell which is the ultimate source of all cells in the root. The apical cell has a tetrahedral shape and divides asymmetrically. The root cap derives from the distal division face, while merophytes derived from three proximal division faces contribute to the root proper. The merophytes are produced sequentially forming three sectors along a helix around the root axis. During development, they divide and differentiate in a predictable pattern. Such growth causes cell pattern of the root apex to be remarkably regular and self-perpetuating. The nature of this regularity remains unknown. This paper shows the 2D simulation model for growth of the root apex with the apical cell in application to Azolla pinnata. The field of growth rates of the organ, prescribed by the model, is of a tensor type (symplastic growth) and cells divide taking principal growth directions into account. The simulations show how the cell pattern in a longitudinal section of the apex develops in time. The virtual root apex grows realistically and its cell pattern is similar to that observed in anatomical sections. The simulations indicate that the cell pattern regularity results from cell divisions which are oriented with respect to principal growth directions. Such divisions are essential for maintenance of peri-anticlinal arrangement of cell walls and coordinated growth of merophytes during the development. The highly specific division program that takes place in merophytes prior to differentiation seems to be regulated at the cellular level.

Understanding mechanisms of rarity in pteridophytes: competition and climate change threaten the rare fern Asplenium scolopendrium var. americanum (Aspleniaceae)

PREMISE OF THE STUDY

Understanding the ecology of rare species can inform aspects of conservation strategies; however, the mechanisms of rarity remain elusive for most pteridophytes, which possess independent and ecologically distinct gametophyte and sporophyte generations. To elucidate factors contributing to recent declines of the rare fern Asplenium scolopendrium var. americanum, we studied the ecology and ecophysiology of its gametophyte generation, focusing on responses to competition, temperature, and water stress.

METHODS

Gametophytes of A. scolopendrium var. americanum, its widespread European relative A. scolopendrium var. scolopendrium, and five co-occurring fern species were grown from spores. Gametophytes were grown at 20°C and 25°C, and germination rates, intra- and interspecific competition, desiccation tolerance, and sporophyte production were determined for all species.

KEY RESULTS

Gametophytes of A. scolopendrium var. americanum had the lowest rates of germination and sporophyte production among all species studied and exhibited the greatest sensitivity to interspecific competition, temperature increases, and desiccation. Mature gametophytes of A. scolopendrium var. americanum grown at 25°C were 84.6% smaller than those grown at 20°C, and only 1.5% produced sporophytes after 200 d in culture. Similar responses were not observed in other species studied.

CONCLUSIONS

The recent declines and current status of populations of A. scolopendrium var. americanum are linked to its gametophyte's limited capacity to tolerate competition and physiological stress linked to climate change. This is the first study to develop a mechanistic understanding of rarity and decline in a fern and demonstrates the importance of considering the ecology of the gametophyte in plants with independent sporophyte and gametophyte generations.

In vitro propagation of a rare medicinal fern of Western Ghats--Diplazium esculentum (Reytz.)

Present study aimed for in vitro culture of circinate part of young leaves of D. esculentum which is amongst the leafy vegetables consumed as vegetable by Paniya and Chetti tribes of Western Ghats. The circinate part of young leaves (crosiers), excised before the beginning of foliar expansion, was inoculated on half strength Murashige and Skoog (MS) medium supplemented with auxins indole-3-butyric acid (IBA) or alpha-napthalene acetic acid (NAA) or 2,4-Dichlorophenoxyacetic acid (2,4-D) and cytokinin 6- benzylaminopurine (BA) in a range 0.5 to 2.5 mg L(-1). Combinations of different concentrations of 2,4 D + BA, IBA + BA as well as of NAA+ BA were also tested in half strength MS medium with 3% sucrose and with pH 5.8. The best morphogenic response was obtained with half strength MS medium supplemented with 2,4-D 0.5 mg L(-1) and BA 2.5 mg L(-1), 3% sucrose, at pH 5.8. For rooting of the microshoots, half strength MS medium supplemented with 2,4-D ( 2 and 1 mg L(-1)) exhibited best results. Present study reports the successful in vitro culturing of D. esculentum.

Cryopreservation of Neottopteris nidus prothallus and green globular bodies by droplet-vitrification

Neottopteris nidus prothalli and green globular bodies (GGBs) were successfully cryopreserved by droplet-vitrification. Prothalli were subjected to different treatments. The following parameters were studied: the age of in vitro mother plants from which prothalli were originated (30 to 90-day old), length of exposure to loading solution (LS) (20 to 40 min) and length of exposure to the plant vitrification solution (PVS2) (10 to 55 min). N. nidus GGBs and GGBs in suspension were subjected to PVS2 for 20, 30 and 40 min before liquid nitrogen exposure. The highest prothalli regrowth (92%) occurred when they were exposed for 40 min to LS, followed by 20 min to PVS2 and when they originated from non-preconditioned 45-day old mother plants. The highest GGB (100%) and GGB suspension regrowth (100%) after cryopreservation occurred when they were exposed to PVS2 for either 20 min or 40 min.

Mycorrhizal fungi modify element distribution in gametophytes and sporophytes of a fern Pellaeaviridis from metaliferous soils

In the present study, the element distribution within mycothallic and nonmycothallic gametophytes and the early stages of sporophyte development of Pellaea viridis (Pteridaceae) were investigated. Gametophytes of this fern were collected from soil samples originating in the ultramafic area of the Agnes Mine near Barberton, South Africa. The gametophytes were grown on both the original soil and on a plant growth substratum obtained from the local botanical garden. Gametophytes and young sporophytes grown on substratum inoculated with Glomus tenue or non-inoculated were freeze-dried, and the distribution of elements was studied using micro-PIXE. The GeoPIXE II software package was used for quantitative elemental mapping complemented by data extracted from arbitrarily selected micro-areas. The obtained results suggest that although the fern itself avoids the uptake of large amounts of heavy metals, increased levels of Ni, Cr, Fe, Co and Ti were found in the part of the gametophyte that hosted the fungal endophyte. This finding suggests that the fungus might be active in the immobilisation of certain potentially toxic metals that are taken up from the soil by the plant, although other mechanisms cannot be excluded. For the first time, precise, quantitative measurements of the concentration of individual elements in the fern gametophytes and young sporophytes were obtained, along with their distribution within the plant parts.

Allelopathy is involved in the formation of pure colonies of the fern Gleichenia japonica

The fern Gleichenia japonica is one of the most widely distributed fern and occurs throughout East to South Asia. The species often dominates plant communities by forming large monospecific colonies. However, the potential mechanism for this domination has not yet been described. The objective of this study was to test the hypothesis that allelochemicals are involved in the formation of G. japonica colonies. An aqueous methanol extract of G. japonica inhibited the growth of seedlings of garden cress (Lepidium sativum), lettuce (Lactuca sativa), ryegrass (Lolium multiflorum) and timothy (Phleum pratense). Increasing extract concentration increased the inhibition. These results suggest that G. japonica contain allelopathic substances. The extract was then purified by several chromatographies with monitoring the inhibitory activity and two growth inhibitory substances causing the allelopathic effect were isolated. The chemical structures of the two substances were determined by spectral data to be a novel compound 3-O-β-allopyranosyl-13-O-β-fucopyranosyl-3β-hydroxymanool (1) and 18-O-α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl-13-epitorreferol (2). These compounds inhibited the shoot and root growth of garden cress, lettuce, alfalfa (Medicago sativa), timothy, ryegrass and barnyardgrass (Echinochloa crus-galli) at concentrations greater than 0.1-1.0mM. The concentrations required for 50% growth inhibition of root and shoot growth of these test plants ranged from 0.72 to 3.49mM and 0.79 to 3.51mM for compounds 1 and 2, respectively. Concentration of compounds 1 and 2 in soil under the pure colony of G. japonica was 4.9 and 5.7mM, respectively, indicating concentrations over those required for 50% growth inhibition are potentially available under monocultural stands of these ferns. Therefore, these compounds may contribute to the allelopathic effects caused by presence of G. japonica and may thus contribute to the establishment of monocultural stands by this fern.

Effects of linuron on a rooted aquatic macrophyte in sediment-dosed test systems

Effects of linuron on the sediment-rooted aquatic macrophyte Myriophyllum spicatum L. were studied in sediment-dosed test systems following a proposed guideline with extended test duration. Sediment, pore water, overlying water and macrophyte shoots were sampled weekly for chemical analyses. Linuron was stable in the sediments. Sediment and pore water concentrations were in equilibrium after 48 h. Overlying water concentrations increased over time, but did not reach equilibrium with pore water concentrations and were 100 times lower. Mass balances showed a rapid uptake of linuron by macrophyte roots. Known pathways and the compound's properties support the conclusion that Myriophyllum takes up linuron from pore water directly through the roots. Hence, effects on macrophytes in this type of sediment toxicity test should be expressed in terms of pore water concentrations. Pore water concentration is the most relevant parameter for describing effects on macrophytes.

Rapid plant invasion in distinct climates involves different sources of phenotypic variation

When exotic species spread over novel environments, their phenotype will depend on a combination of different processes, including phenotypic plasticity (PP), local adaptation (LA), environmental maternal effects (EME) and genetic drift (GD). Few attempts have been made to simultaneously address the importance of those processes in plant invasion. The present study uses the well-documented invasion history of Senecio inaequidens (Asteraceae) in southern France, where it was introduced at a single wool-processing site. It gradually invaded the Mediterranean coast and the Pyrenean Mountains, which have noticeably different climates. We used seeds from Pyrenean and Mediterranean populations, as well as populations from the first introduction area, to explore the phenotypic variation related to climatic variation. A reciprocal sowing experiment was performed with gardens under Mediterranean and Pyrenean climates. We analyzed climatic phenotypic variation in germination, growth, reproduction, leaf physiology and survival. Genetic structure in the studied invasion area was characterized using AFLP. We found consistent genetic differentiation in growth traits but no home-site advantage, so weak support for LA to climate. In contrast, genetic differentiation showed a relationship with colonization history. PP in response to climate was observed for most traits, and it played an important role in leaf trait variation. EME mediated by seed mass influenced all but leaf traits in a Pyrenean climate. Heavier, earlier-germinating seeds produced larger individuals that produced more flower heads throughout the growing season. However, in the Mediterranean garden, seed mass only influenced the germination rate. The results show that phenotypic variation in response to climate depends on various ecological and evolutionary processes associated with geographical zone and life history traits. Seeing the relative importance of EME and GD, we argue that a “local adaptation vs. phenotypic plasticity” approach is therefore not sufficient to fully understand what shapes phenotypic variation and genetic architecture of invasive populations.