Azolla Species Research Articles

Transferability of Genic-SSR markers developed from the transcriptome data of Selaginella bryopteris (L.) Baker

In the present study, the experimental validation of Genic-SSR markers developed from transcriptome data of Selaginella bryopteris was done, and their cross-species transferability was examined across genus and species of pteridophytes. Twenty primer pairs were designed to amplify the various repeats of SSR markers, and first validated with complementary DNA (cDNA) of S. bryopteris. Out of twenty primer pair, fourteen primer pairs (70%) could amplify the DNA of S. bryopteris. Among Azolla spp., four SSR markers (SbSSR4, SbSSR12, SbSSR14 and SbSSR18) were found to be 100% transferable, while others SbSSR13 (80%), SbSSR3 and SbSSR20 (50%) and four markers SbSSR6, SbSSR10, SbSSR15 and SbSSR19 (10%). Out of twenty validated primers, 11 primers were found to be polymorphic. The value of polymorphism information content (PIC) ranged from 0.47 to 0.86 with an average of 0.49. The Jaccard’s similarity coefficient ranged from 0.10 to 0.93 which revealed a wide range of genetic identity. The similarity between A. fuliculoids and A. maxicana (0.93), and A. pinnata and A. rubra (0.93) was high and while low similarity coefficient of S. bryopteris with P. vittata (0.18), local fern (0.20) and with Azolla spp. (0.10- 0.25). Two major Clusters formed based on UPGMA i.e. S. bryopteris, P. vittata, local fern in Cluster I and Azolla spp. in Cluster II, a clear divergence between S. bryopteris and other pteridophytes. BAUS1 was found to be more genetically divergent followed by BAUS2, BAUS1 and BAUS3 in comparison to known species of Azolla. The transferability of Genic- SSR markers of S. bryopteris demonstrated the utility for elucidating genetic relationship among selected pteridophytes.

Morphological and Molecular Phylogenetic Analyses Reveal a New Record to the Flora of Iraq: Azolla filiculoides

       Azolla filiculoides is an aquatic fern native to Americas. The species has dispersed through Europe and Asia. Recently, it has been identified in northern part of Iran. However, there is no evidence confirms the presence of Azolla sp. in Kurdistan region of Iraq. The aim of the present study was to identify the species of Azolla found in Tanjaro river/northern part of Iraq. We studied morphological characteristics including trichomes, leaf branches, and three phylogenetic positions such as rbcl, rps4 and trnG-trnR of the species. The morphological and phylogeny investigations were compared with other identified species (reference species). Our results showed that the morphological characteristics are more similar to Azolla filicluloides than other species. Based on the phylogenetic trees, the position of the observed species was closer to Azolla filiculoides than others. These results indicated that the Azolla species found in Tanjaro river is more likely c.

Azolla Sporophytes and Spores from the Late Cretaceous and Paleocene of Patagonia, Argentina

Premise of research. While Azolla has a rich fossil record based on dispersed megaspore apparatuses and microspore massulae, fossil sporophytes are relatively rare. In this contribution, we describe two fossil Azolla species based on both sporophytes and spores from Chubut Province, Patagonia, Argentina: Azolla coloniensis De Benedetti & Zamaloa, emend. Hermsen et al., and A. keuja Jud et al., sp. nov. Azolla coloniensis and A. keuja are the first fossil species of Azolla to be represented by vegetative structures (i.e., leaves, stems, and roots) from both South America and the Southern Hemisphere.Methodology. We examined sporophyte material of A. coloniensis from the Cañadón del Irupé locality, Upper Cretaceous, La Colonia Formation, and A. keuja from the Palacio de los Loros locality PL-2, Paleocene, Salamanca Formation. Spores of A. keuja were obtained from a sporophyte specimen and its surrounding rock matrix. Material was studied using standard light microscopy, epifluorescence microscopy, and scanning electron microscopy. Fossils are held at the Museo Paleontológico Egidio Feruglio, Trelew, Chubut Province, Argentina.Pivotal results. Azolla coloniensis produced many-floated megaspore apparatuses and microspore massulae with anchor-tipped glochidia, placing it in the fossil Azolla section Florschuetzia. Azolla keuja sporophytes are structurally similar to those produced by the extant African species A. nilotica and the Late Cretaceous–Paleocene North American species A. schopfii in overall size, growth form, leaf structure, and production of fascicled roots; while all three taxa produce similar microspore massulae, the structure of their megaspore apparatuses differ. Azolla keuja cannot be assigned to any section of Azolla.Conclusions. Azolla coloniensis and A. keuja are important because they provide two new organismal concepts for extinct species of Azolla. Our inability to fully classify A. keuja to section, in combination with the great morphological diversity of fossil Azolla, indicates that a comprehensive reevaluation of phylogeny and taxonomy that incorporates both extant and fossil species is needed.

Hyperaccumulation of Cu, Zn, Ni, and Cd in Azolla species inducing expression of methallothionein and phytochelatin synthase genes

Azolla is a floating aquatic fern, having amazing capacity for concentrating toxic heavy metals. Metallothioneins (MTs) and phytochelatins (PCs) are well-defined heavy metal-binding ligands in plants. Bioaccumulation potential of different Azolla species varies according to their heavy metal ions. Therefore, the accumulation of Ni, Zn, Cu, and Cd was studied in A. pinnata, A. filiculoides, and a sample taken from Anzali wetland. Moreover, the expression of metallothionein and phytochelatin synthase encoding genes was examined at different metal concentrations. The highest level of Cu and Cd absorption was detected in A. pinnata, while the maximum amount of Ni and Zn absorption was observed in A. filiculoides and the sample taken from Anzali, respectively. The MT2 and PCS1 gene expression patterns were significantly induced by the heavy metal treatments, confirming their roles in phytoremediation potential of Azolla. However, as the results concerning heavy metal accumulation and gene expression vary in different species, only specific species of Azolla can be used for special purposes. It can be concluded that the Azolla is a good candidate for phytoremediation purposes, and the formation of phytochelatin-heavy metal complexes and their sequestration in vacuole are the main processes influencing susceptibility of Azolla to heavy metals.

Cyanobiont diversity in six Azolla spp. and relation to Azolla-nutrient profiling.

Illumina-Miseq®-based cyanobiont diversity and biomass were analyzed in six Azolla spp. Results revealed that 93-98% of total operational taxonomic units (OTUs) belong to Nostacaceae followed by Cylindrospermopsis with about 1-6% OTUs. The taxonomy of Azolla-cyanobiont is a long-term debate within the scientific community. Morphological and biochemical-based reports indicated the presence of Anabaena, Nostoc and/or Trichormus azollae as abundant Azolla-cyanobionts, however, molecular data did not support the abundance of Anabaena and/or Nostoc. To understand furthermore, the cyanobiont diversity in six species of Azolla (A. microphylla, A. mexicana, A. filiculoides, A. caroliniana, A. pinnata and A. rubra) was analyzed based on 16S rRNA Illumina-MiSeq sequencing. Additionally, biomass and nutrient profiling of Azolla spp. were analyzed and correlated with cyanobiont diversity. Illumina-MiSeq data revealed that 99.6-99.9% of total operational taxonomic units (OTUs) belonged to Nostocophycideae (class), Nostocales (order) and Nostacaceae (family). At genus level, the unassigned affiliation (93.4-97.9%) under Nostacaceae family was abundant followed by Cylindrospermopsis OTUs (1.1-6.0%). Interestingly, A. pinnata harboured maximum Cylindrospermopsis OTUs and also recorded higher biomass (40.67gm-2day-1), whereas crude protein (25.9%) and antioxidants (76.9%) were recorded to be higher in A. microphylla. Biplot analysis revealed that A. pinnata and its cyanobiont abundance were positively correlated with neutral and acid detergent fibers. Overall, the present findings deepened the understanding about cyanobiont in Azolla and its relations with Azolla nutrient profiling.

ω20-Hydroxy and ω9,ω10-dihydroxy biomarker lipids in ferns from the Salviniaceae family

All seven species of floating ferns from the genus Azolla (family Salviniaceae) produce a unique series of long chain mid-chain ω20-hydroxy compounds (ω20-alkanols, 1,ω20-diols, ω20-hydroxy fatty acids) and structurally related ω9,ω10-dihydroxy compounds (ω9,ω10-diols, 1,ω9,ω10-triols and ω9,ω10-dihydroxy fatty acids). These very long chain fatty acid (VLCFA) derivatives occur in the ferns’ waxes in free and esterified form. The specific distribution of these lipids differed between species belonging to each of the two sections in the Azolla genus: in species of the section Azolla and Rhizosperma, the ratio of C31 over C35 ω20-alkanols averaged 7.0 and 0.40, and the ratio of C26 over C28 ω20-hydroxy fatty acids averaged 2.7 and 1.0, respectively. Similar compounds were identified in species of another genus in the Salviniaceae family, Salvinia, suggesting that their biosynthetic pathway evolved early during Salviniaceae evolution (>89 Ma). Salvinia species contain ω20-hydroxy and ω9,ω10-dihydroxy compounds in smaller concentrations and in a much different distribution compared to Azolla; the C31 1,ω20-diol is unique to Salvinia species. Closely related fern species from the genera Marsilea, Pilularia and Regnellidium did not contain these compounds, nor did unrelated aquatic plants from the genera Lemna and Pistia. All mid-chain hydroxy compounds detected in extant Azolla have been traced previously in Arctic Eocene sediments from the so-called ‘Azolla Event’ (48.5 Ma), implying that they are well preserved in the geological record and may therefore serve as Azolla biomarkers. Our findings indicate that ω20-hydroxy and ω9,ω10-dihydroxy compounds in sediments could be used as biomarkers of the whole Salviniaceae family. Subsequently, the clear differences in compound distribution between the Azolla and Salvinia genera and the more subtle ones between the two Azolla sections, may allow assigning the compound’s origin at the genus (and possibly section) level, depending on the preservation of compound classes in the sediment and the timing of the Azolla or Salvinia deposition. This is exemplified by a sediment interval of the so-called ‘Salvinia bed’ (Eemian), which contained trace amounts of the C31 1,ω20-diol, but none of the ω20-hydroxy and ω9,ω10-dihydroxy compounds common to Azolla, indicating the value of C31 1,ω20-diol as a biomarker for distinguishing Salvinia from Azolla.

Impact of climate on biomass production of Azolla in Bihar

Widely cultivated in the Asian regions, Azolla is either incorporated into the soil before rice transplanting or grown as a dual crop along with rice. To examine the feasibility of its use in flooded rice fields, the study was conducted during 2011-13 with 9 different species/ strains of Azolla at BAU Sabour, to study the growth-development dynamics and the resistance/tolerance to extreme temperature which generally occurs in the area. Azolla biomass increased during February- April but suddenly decreased during May-June and again increased during July-September thereafter, biomass decreased during October-January. The correlation coefficient between biomass growth rate of strains A. faliculoides, A. microphylla and BAUAS-1 of Azolla and maximum temperature was found significantly positive. Significant positive correlation between biomass production of species A. faliculoides and strain BAUAS-1 with minimum temperature was found 0.70 and 0.62 respectively, which indicates that increase in minimum temperature up to limit, may increase the growth rate in these strain/spp. There was significant negative correlation (0.70, 0.63 and 0.68) between biomass production rate and relative humidity measured at morning, in the species/strain A. rubra, BAUAS-1, BAUAS-2 respectively. Biomass production rate of azolla species A. pinnata showed significant negative correlation with relative humidity at evening. Significant positive correlation between biomass production and rainfall during the growth period in species A. faliculoides was found, which indicates rainfall or sufficient water increases the growth in Azolla.

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

Summary 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 N2O 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. 15N2 incorporation was active in ferns with N. azollae but not in ferns without. N2O 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 N2O.

New record of Ephestiopsis vishnu (Lepidoptera, Pyralidae) from Japan, a candidate to be a biological control agent for exotic Azolla species

New record of Ephestiopsis vishnu (Lepidoptera, Pyralidae) from Japan, a candidate to be a biological control agent for exotic Azolla species

Microcosm investigation of growth and phytoremediation potential of Azolla japonica along nitrogen gradients

ABSTRACTAlthough Azolla species are among the most promising plants for use in phytoremediation, more studies on their growth and nitrogen (N) uptake along the N gradients of growing media are required. In this study, N concentration-dependent growth in growing media and phosphorus (P) and N accumulation by Azolla japonica were studied by estimating direct N uptake from media by molybdenum-iron proteins. The doubling time of A. japonica was less than a week, regardless of the N concentration (0, 5, and 25 mg N/L) present in the growth media, indicating that this plant is suitable for remediation. Plants showed a high uptake of P, probably via plant-bacteria symbiosis, indicating their potential for effective P remediation. A. japonica also showed more than 4% N content regardless of the treatment and accumulated more than 40 mg of N per microcosm in 3 weeks. iron and molybdenum levels in plants were strongly associated with N fixation, and N uptake from media was estimated to be more than 25 mg per microcosm in 3 weeks, indicating that A. japonica has N remediation potential. As A. japonica is a rapidly growing plant, capable of efficient P and N remediation, it has great potential for use in phytoremediation of nutrient-enriched waters such as agricultural or urban wastewater and eutrophicated aquatic ecosystems.

Reinterpretation of Azolla primaeva (Azollaceae, Eocene, Canada) using electron microscopy and X-ray tomographic microscopy

Azolla primaeva (Penhallow) Arnold fertile whole plants from the lower Eocene of Driftwood Creek, Canada have been examined using LM, SEM, TEM and SRXTM methods on hand specimens and sieved residues. The new data have resulted in an emended diagnosis. The megaspore is partly covered by filosum and the wall lacks excrescences. The exoperine is highly variable with nodular, to clavate, baculate and tabulate elements, which fuse to form a foveolate to reticulate megaspore surface, which is complex and contorted. Glochidia on the microspore massulae are sometimes septate and the flukes on their anchor-shaped tips are variable, some being long, narrow and wavy, others shorter and broad and a few are recurved. Hairs are lacking on the massula surface and glochidia. The organization of the float zone of the megaspore apparatus has always been controversial with 0, 1, 3 or 9 floats proposed. The new results show that there are no pseudovacuolate floats. By contrast, the ‘float’ zone consists of bundles of modified granular and filamentous endoperine elements surrounded by bundles of broader suprafilosum hairs. The absence of pseudovacuolate floats in A. primaeva is suggested to be an important character for phylogenetic analyses. The high variability in glochidia tips, glochidia septa and exoperine organisation is unusual within the genus Azolla. The new data on A. primaeva are compared with the other two whole plant Azolla species from Canada (Azolla stanleyi and Azolla schopfii) and with dispersed Azolla reproductive structures from Canada including the Arctic. This confirms that all are distinct species.

Aquatic plant Azolla as the universal feedstock for biofuel production.

BackgroundThe quest for sustainable production of renewable and cheap biofuels has triggered an intensive search for domestication of the next generation of bioenergy crops. Aquatic plants which can rapidly colonize wetlands are attracting attention because of their ability to grow in wastewaters and produce large amounts of biomass. Representatives of Azolla species are some of the fastest growing plants, producing substantial biomass when growing in contaminated water and natural ecosystems. Together with their evolutional symbiont, the cyanobacterium Anabaena azollae, Azolla biomass has a unique chemical composition accumulating in each leaf including three major types of bioenergy molecules: cellulose/hemicellulose, starch and lipids, resembling combinations of terrestrial bioenergy crops and microalgae.ResultsThe growth of Azolla filiculoides in synthetic wastewater led up to 25, 69, 24 and 40 % reduction of NH4–N, NO3–N, PO4–P and selenium, respectively, after 5 days of treatment. This led to a 2.6-fold reduction in toxicity of the treated wastewater to shrimps, common inhabitants of wetlands. Two Azolla species, Azolla filiculoides and Azolla pinnata, were used as feedstock for the production of a range of functional hydrocarbons through hydrothermal liquefaction, bio-hydrogen and bio-ethanol. Given the high annual productivity of Azolla, hydrothermal liquefaction can lead to the theoretical production of 20.2 t/ha-year of bio-oil and 48 t/ha-year of bio-char. The ethanol production from Azolla filiculoides, 11.7 × 103 L/ha-year, is close to that from corn stover (13.3 × 103 L/ha-year), but higher than from miscanthus (2.3 × 103 L/ha-year) and woody plants, such as willow (0.3 × 103 L/ha-year) and poplar (1.3 × 103 L/ha-year). With a high C/N ratio, fermentation of Azolla biomass generates 2.2 mol/mol glucose/xylose of hydrogen, making this species a competitive feedstock for hydrogen production compared with other bioenergy crops.ConclusionsThe high productivity, the ability to grow on wastewaters and unique chemical composition make Azolla species the most attractive, sustainable and universal feedstock for low cost, low energy demanding, near zero maintenance system for the production of a wide spectrum of renewable biofuels.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0628-5) contains supplementary material, which is available to authorized users.

Interactive effects of herbicide and enhanced UV-B on growth, oxidative damage and the ascorbate-glutathione cycle in two Azolla species

A field experiment was conducted to investigate the impact of alone and combined exposures of herbicide pretilachlor (5, 10 and 20μgml−1) and enhanced UV-B radiation (UV-B1; ambient +2.2kJm−2 day−1 and UV-B2; ambient +4.4kJm−2 day−1) on growth, oxidative stress and the ascorbate-glutathione (AsA-GSH) cycle in two agronomically important Azolla spp. viz., Azolla microphylla and Azolla pinnata. Decreased relative growth rate (RGR) in both the species under tested stress could be linked to enhanced oxidative stress, thus higher H2O2 accumulation was observed, that in turn might have caused severe damage to lipids and proteins, thereby decreasing membrane stability. The effects were exacerbated when spp. were exposed to combined treatments of enhanced UV-B and pretilachlor. Detoxification of H2O2 is regulated by enzymes/metabolites of AsA-GSH cycle such as ascorbate peroxidase (APX) and glutathione reductase (GR) activity that were found to be stimulated. While, dehydroascorabte reductase (DHAR) activity, and the amount of metabolites: ascorbate (AsA), glutathione (GSH) and ratios of reduced/oxidized AsA (AsA/DHA) and GSH (GSH/GSSG), showed significant reduction with increasing doses of both the stressors, either applied alone or in combination. Glutathione-S-transferase (GST), an enzyme involved in scavenging of xenobiotics, was found to be stimulated under the tested stress. This study suggests that decline in DHAR activity and in AsA/DHA ratio might have led to enhanced H2O2 accumulation, thus decreased RGR was noticed under tested stress in both the species and the effect was more pronounced in A. pinnata. Owing to better performance of AsA-GSH cycle in A. microphylla, this study substantiates the view that A. microphylla is more tolerant than A. pinnata.

Molecular identification of Azolla invasions in Africa: The Azolla specialist, Stenopelmus rufinasus proves to be an excellent taxonomist

Biological control of Azolla filiculoides in South Africa with the Azolla specialist Stenopelmus rufinasus has been highly successful. However, field surveys showed that the agent utilized another Azolla species, thought to be the native Azolla pinnata subsp. africana, which contradicted host specificity trials. It is notoriously difficult to determine Azolla species based on morphology so genetic analyses were required to confirm the identity of the Azolla used by the agent. Extensive sampling was conducted and samples were sequenced at the trnL-trnF and trnG-trnR chloroplastic regions and the nuclear ITS1 region. Current literature reported A. filiculoides as the only Section Azolla species in southern Africa but 24 samples were identified as Azolla cristata, an introduced species within Section Azolla that was not used during host specificity trials. A. pinnata subsp. africana was only located at one site in southern Africa, while the alien A. pinnata subsp. asiatica was located at three. What was thought to be A. pinnata subsp. africana was in fact A. cristata, a closer relative of A. filiculoides and a suitable host according to specificity trials. This study confirms that S. rufinasus is a proficient Azolla taxonomist but also supports the use of molecular techniques for resolving taxonomic conundrums.

Evaluating the combined effects of pretilachlor and UV-B on two Azolla species

The present study assessed the comparative responses of two agronomic species of Azolla (A.microphylla and A. pinnata) exposed to man-made and natural stressors by evaluating biomass accumulation, pigments (chlorophyll a and b and carotenoid contents), photosynthetic activity and nitrogen metabolism. The study was carried out in field where two species of Azolla were cultured and treated with various concentrations (5, 10 and 20μgml−1) of herbicide; pretilachlor [2-chloro-2,6-diethyl-N-(2-propoxyethyl) acetanilide] and enhanced levels (UV-B1: ambient +2.2kJm−2day−1 and UV-B2: ambient +4.4kJm−2day−1) of UV-B, alone as well as in combination. Biomass accumulation, photosynthetic pigments; chlorophyll a, b and carotenoids, photosynthetic oxygen yield and photosynthetic electron transport activities i.e. photosystem II (PS II) and photosystem I (PS I) in both the species declined with the increasing doses of pretilachlor and UV-B radiation, which further declined when applied in combination. The lower doses (5 and 10μgml−1) of pretilachlor and UV-B (UV-B1 and UV-B2) alone, damaged mainly the oxidation side of PS II, whereas higher dose (20μgml−1) of pretilachlor alone and in combination with UV-B1 and UV-B2 caused damage to PS II reaction centre and beyond this towards the reduction side. A significant enhancement in respiration was also noticed in fronds of both the Azolla species following pretilachlor and UV-B treatment, hence indicating strong damaging effect. The nitrate assimilating enzymes – nitrate reductase and nitrite reductase and ammonium assimilating enzymes – glutamine synthetase and glutamate synthase were also severely affected when treated either with pretilachlor and/or UV-B while glutamate dehydrogenase exhibited a stimulatory response. The study suggests that both the species of Azolla showed considerable damage under pretilachlor and UV-B treatments alone, however, in combination the effect was more intense. Further, in comparison to A. pinnata, A. microphylla exhibited greater resistance against tested doses of both the stresses, either alone or in combination.

Bioactivity of Azolla aqueous and organic extracts against bacteria and fungi

Previous reports indicate the use of the aquatic fern Azolla as medicinal plant in New Zealand and Tanzania against sore throat and cough, respectively. Therefore, the aims were to evaluate the bioactivity of Azolla organic and aqueous extracts against bacteria and yeasts. Organic (dichloromethane:methanol) and aqueous extracts obtained from six Azolla species were tested against bacterial pathogenic and non-pathogenic strains (four Gram-positive and three Gram-negative) and pathogenic fungi (three clinical isolates of Candida albicans and one of C. glabrata), using the agar diffusion method and the broth microdilution assay. The results showed that organic extracts of A. caroliniana and A. rubra and of A. filiculoides inhibited the growth of B. subtilis ATCC 6633 whereas those of A. caroliniana and A. microphylla inhibited the growth of S. aureus ATCC 25923. The MICs were higher than 4 mg/ml for A. caroliniana, A. microphylla and A. rubra and higher than 3.25 mg/ml for A. filiculoides. Aqueous extracts of A. filiculoides, A. caroliniana, A. microphylla, A. rubra and A. pinnata var. pinnata induce a small inhibition zone (1 mm) in C. albicans ATCC 10231 with a MIC higher than 12.5 mg/ml. In conclusion, organic and aqueous extracts of some Azolla species show potential for use against infections caused by Gram-positive bacteria and C. albicans, respectively.

Anticaries Activity of <i>Azolla pinnata</i> and <i>Azolla rubra</i>

The present study was carried out to investigate anticaries activity of two Azolla species viz., A. pinnata and A. rubra . Inhibitory efficacy of methanolic extract of both Azolla species was tested against six oral isolates of Streptococcus mutans by Agar well diffusion and Minium inhibitory concentration (MIC) determination. The S. mutans isolates were shown to be susceptible to extracts. Among Azolla species, A. pinnata displayed high inhibitory effect against oral isolates when compared to A. rubra as evidenced by wider inhibition zones and low MIC values. These Azolla species can be used to treat dental caries. Keywords : Azolla Dental caries Agar well diffusion

Identity and origins of introduced and native Azolla species in Florida

Azolla pinnata, an introduced aquatic fern, is spreading rapidly causing concern that it may displace native Azolla. It is now present in the Arthur R. Marshall Loxahatchee National Wildlife Refuge, the northernmost portion of the Florida Everglades. Because A. pinnata subspecies are native to Africa, Southeast Asia, and Australia, determining the actual geographic origin of the Florida exotic is important to the discovery of efficacious biological control agents. Both the exotic and native Azollas were examined using morphological and molecular criteria. Both criteria distinguished three A. pinnata subspecies with the Florida exotic matching the Australian A. pinnata subsp. pinnata. Molecular divergence between the A. pinnata subspecies indicates the three types should be considered separate species. The Florida native was characterized by both molecular and morphological methods as Azolla caroliniana. The discovery of a previously uncharacterized Ecuadorian Azolla, which appears to be a paternal ancestor of A. caroliniana, indicates that A. caroliniana is a hybrid species.

THE AZOLLA-ANABAENA SYMBIOSIS: MORPHOLOGY, PHYSIOLOGY AND USE

ABSTRACT Heterosporous ferns of the genus Azolla contain an N2-fixing cyanobacterium, designated Anabaena azollae, in specialized leaf chambers. Our studies of the symbiosis per se have been primarily restricted to A. caroliniana. However, comparative studies have encompassed four of the six known Azolla species: A flliculoides, A. mexicana and A. pinnata, in addition to A. caroliniana. The physiological, biochemical, morphological and ultrastructural studies which support a current hypothesis of host-symbiont interactions and structure-function relationships are described. The latter is largely based on recent studies of the ontogenetic sequence of leaf development and associated events in the symbiotic cyanobacterium. Under optimal growth conditions the four Azolla species double their biomass within two days and maintain an N content of 5–6% of the dry weight with N2 as the only N source. Results of subsequent comparative studies of photosynthesis, respiration, nitrogen fixation and associated processe...

The freshwater fern Azolla (Azollaceae) from Eocene Arctic and Nordic Sea sediments: New species and their stratigraphic distribution

Three new species of the freshwater fern Azolla are described from Eocene marine deposits of the Arctic and Nordic seas, bringing the total number of species now documented from these areas to five. Azolla arctica Collinson et al., Azolla jutlandica Collinson et al., Azolla nova sp. nov. and Azolla nuda sp. nov. are known from both megaspore apparatuses and microspore massulae, and occur at more than one site. Their microspore massula characters are sufficiently distinctive to allow their recognition in palynological preparations. Presence or absence of hairs on the microspore massula surface and glochidia bases is shown to be a useful species diagnostic character and is worthy of greater attention in Azolla taxonomy. The fifth species, Azolla astroborealis sp. nov., is only known from a few megaspore apparatuses in the Northstar 1 Well in the western Arctic, but these are strikingly different from those of the other four species e.g., in having nine distinct pseudovacuolate floats.Samples from cores and most individual sites contain more than one Azolla species. This indicates that conditions were particularly favourable for growth of Azolla for a prolonged time interval in the latest early and possibly earliest middle Eocene (latest Ypresian and earliest Lutetian) around the western Arctic and the Norwegian–Greenland Sea.