Metal removal by immobilised and non-immobilised Azolla filiculoides

Milled-sieved and epichlorhydrin-immobilised Azolla biosorbed ca. 363 and 320 mol Cu²⁺ g^–1 from a 100 mg l^–1 solution. Efficiency of Cu²⁺ removal by columns was in the order epichlorohydrin-immobilised Azolla>milled-sieved Azolla>untreated Azolla. The 2.5 g epichlorohydrin-immobilised Azolla column demonstrated complete metal sequestration from ca. 12 l of influent 5 mg Cu²⁺ l^–1 and was still at less than 75% saturation even after ca. 22 l had passed through the column. EDTA effectively desorbed Cu²⁺ with a ca. 55-fold decrease in volume.     

Immunocytochemical localization of cytokinin in Azolla filiculoides

Abstract

In the small aquatic fern Azolla filiculoides, cytokinin immunolocalization was performed in longitudinal axial sections of plantlet shoots. The reaction was detected: (i) in the contiguous cell sheet which encircles vascular tissues, (ii) in shoot and root meristem target cells, and (iii) in the teat cells of the leaf cavity pore. Our results demonstrate, for the first time, that in ferns the cytokinin translocation pattern can be different to that described in seed plants. Thus, this class of hormones is translocated, via vascular tissues in seed plants, whereas in Azolla it depends upon a sheet layer of cells encircling the conducting tissues. In shoot and root meristems, cytokinin distribution widely differs; in fact, in the shoot apex, the signal is present only in a few target cells, whereas in the root the signal is localized in numerous contiguous cells. Another finding concerns the clear signal observed at the level of the teat cells delimiting the pore which connect the leaf cavity with the exterior. This result provides indication that cytokinins, which are known to be involved also in light perception, might play a key role in the control of Anabaena movement into and out of the leaf cavity. This is the first report concerning cytokinin distribution in fern cells and tissues. Our results suggest that these hormones are implicated in the different plant organs in very different and specific functions.     

Culture of Azolla filiculoides in artificial conditions

Abstract

Azolla filiculoides showed a planar development in four culture media, but with overlapping of sporophytes after 28 days, and curled roots in all cases except for IRRI2. The difference in biomass between the media IRRI2 and IRRI1‐Fe10x was statistically significant at Days 14, 21 and 28 by ANOVA. Medium IRRI2 gave the highest duplication time.     

Batch studies on the removal of gold(III) from aqueous solution by Azolla filiculoides

Azolla filiculoides removed 86% and 100% of gold(III) from initial metal solutions of 2–10 mg gold l^–1 increasing with increased initial concentrations of gold(III). The biomass gave greater than 95% removal efficiency from solution at all biomass concentrations measured. Complete removal of gold occurred at pH 2, with 42% removal at pH 3 and 4, and 63% and 73% removal at pH 5 and 6, respectively. No temperature-dependence removal was observed.     

Phytoremediation of petroleum hydrocarbons by using a freshwater fern species Azolla filiculoides Lam

In this study, the phytoremediation capacity of Azolla filiculoides Lam. for the water resources contaminated with petroleum hydrocarbons was investigated. The plants were grown in nitrogen-free Hoagland nutrient solution containing 0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% crude oil under greenhouse conditions for 15 days. Although the growth rate of the plants were not negatively influenced by the presence of crude oil in the media for the concentration of 0.005% and 0.01% v/v, a gradual impeding effect of crude oil in the growth media has been observed at concentrations 0.05–0.1%. More than 0.1% crude oil in the growth medium ostensibly retarded the growth. For example, 0.2% oil in the media reduced growth approximately 50% relative to the control, and the presence of crude oil at concentrations 0.3% or more were lethal. The data about the percentage of plant growth, fresh weight increase and root growth clearly indicated that the tolerance level of A. filiculoides plants to crude oil ranges between 0.1% and 0.2%. In comparison to control samples, the biodegradation rate of total aliphatic and aromatic (phenathrene) hydrocarbons at 0.05–0.2% oil concentrations, was 94–73% and 81–77%, respectively. On the other hand, in case of further increases in oil concentration in media, i.e.; 0.3–0.5%, the biodegradation rate was still higher in the experimental samples, respectively 71–63% and 75–71%. The high biodegradation rates of petroleum hydrocarbons in the experimental samples suggested that A. filiculoides plants could be a promising candidate to be used for the phytoremediation of low crude oil contaminated precious freshwater resources.     

Contribution of Azolla filiculoides to hydrazine elimination from water

Wetlands Ecology and Management - In this research we report the significant effect of the floating water fern Azolla filiculoides on the elimination of hydrazine (N2H4) from water, which is a...     

Response of growth and antioxidant enzymes in Azolla plants (Azolla pinnata and Azolla filiculoides) exposed to UV-B

Effect of ultravilolet-B (0.4 Wm(-2)) irradiation on growth, flavonoid content, lipid peroxidation, proline accumulation and activities of superoxide dismutase and peroxidase was comparatively analysed in Azolla pinnata and Azolla filiculoides. Growth measured as increment in dry weight reduced considerably due to all UV-B treatments. However, the reduction was found to be severe in A. filiculoides as compared to A. pinnata. The level of UV-absorbing compound flavonoids increased significantly in A. pinnata plants whereas only a slight increase in the flavonoid content was observed in A. filiculoides. UV-B exposure led to enhanced production of malondialdehyde (MDA) and electrolyte leakage in A. filiculoides than A. pinnata. Proline accumulation also showed a similar trend. Marked differences in the activity of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD) was noticed in both the plants exposed to UV-B. Our comparative studies indicate A. pinnata to be better tolerant to UV-B as compared with A. filiculoides which appears to be sensitive.     

Differential response of antioxidant enzymes to salinity stress in two varieties of Azolla (Azolla pinnata and Azolla filiculoides)

The activity and modulation of antioxidant components were comparatively analyzed in two varieties of Azolla (Azolla pinnata and Azolla filiculoides) under different concentrations of NaCl. The total superoxide dismutase (SOD) and ascorbate peroxidase (APX) activity increased in A. pinnata, whereas both enzyme activities decreased in A. filiculoides. The plants of A. pinnata exposed to 30 mM NaCl contained a lower amount of Na⁺ ions and showed a lower electrolyte leakage than A. filiculoides. Our studies indicate a differential response of antioxidant enzymes in relation to salt tolerance in Azolla plants. On the basis of our comparative analysis, A. pinnata has been ranked salt tolerant as compared with A. filiculoides, which is salt sensitive.     

Isolation of Hair Cells from Azolla filiculoides var. japonica Leaves

A procedure has been developed to isolate hair cells from Anabaenacontaining packets of the aquatic fern Azolla. Unbroken algalpackets, isolated by enzyme treatment and flotation on 12.5%Percoll solution, contained hair cells, Anabaena filaments andthe envelope membrane. When the packet suspension was gentlypipetted, hair cells attached to the envelope membrane becamedetached from the Anabaena filaments. Hair cells were separatedby flotation on 34% Percoll solution and further purified bysifting through nylon mesh. Both branched and unbranched cellswere isolated and about 70% remained unstained by 0.1% trypanblue. Electron microscopic observation showed that these cellswere protoplasts enclosed by a thin envelope and had well preservedinternal structures. The activities of ammonia-assimilatingenzymes in the hair cells were much higher than those in Azollaleaves, while the activities in the endophytes were repressedto very low levels. These results suggest that hair cells playan important role in the assimilation of the nitrogen whichthe endophytes fix and release into the cavity. (Received March 24, 1986; Accepted June 28, 1986)     

Performance of Dead Azolla filiculoides Biomass in Biosorption of Au from Wastewater

Dried milled biomass of Azolla filiculoides removed up to 98.2% of gold from wastewater from a gold plating factory containing 5 mg gold/l in solution in batch biosorption. The gold uptake capacity of the biomass was 98 mg/g. Whole dried biomass used in a continuous flow column removed up to 100% of gold from diluted wastewater. A similar column was linked to a sulphide precipitation process to provide a two-step system which was able to remove 98% of gold from undiluted wastewater containing 41 mg Au/l. The lifetime of the column was five days.     

Interacting effects of atmospheric CO2 enrichment and solar radiation on growth of the aquatic fern Azolla filiculoides

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Growth and survival of Azolla filiculoides in Britain I. Vegetative production

Azolla filiculoides Lam. causes serious weed problems in Britain, but its long-term survival might be limited by winter death. The aim of this study was to establish the low temperature responses and limitations of A. filiculoides sporophytes.
In the laboratory, normal vegetative growth was shown to continue at 5°C. Reddening of plants was a response to low temperature and high light conditions which could be prevented by shading. Adult plants died after short (18 h) exposure to −4°C but survived sub-zero temperatures >−4°C. Evidence was found of seasonal changes in chill tolerance, but not in freeze tolerance.
In outdoor culture, plants survived encasement in ice and air temperatures to −5°C. Additional evidence suggested that natural populations can readily survive air temperatures much lower than this. Microclimatic effects are likely to be responsible for this discrepancy between laboratory and outdoor culture results.
Three phenotyes were identified; survival, colonizing and mat forms.     

Growth and survival of Azolla filiculoides in Britain. II. Sexual reproduction

Sporulation in the floating fern Azolla filiculoides Lam. is both frequent and widespread in Britain and might therefore play a greater part in the population dynamics of the species than has been suggested by earlier reports. In laboratory experiments, increasing plant density and/or phosphorus supply resulted in increased sporulation. It was estimated that a thick mat of 8 kg m² fresh biomass can produce 380000 microsporocarps and 85000 megasporocarps per m².
Light and temperatures >10°C were necessary for sporocarp germination. Sporocarps could survive exposure to both low temperatures (5°C for at least 3 months) and sub-zero temperatures (−10°C for at least 18 d). Sporocarps were found to survive storage in water for 3 yr and to germinate from mud samples collected in the field. In laboratory culture, sporeling growth and survival were optimal at 15°C.
There is some evidence that A. filiculoides might have adapted to the British climate since its introduction.     

Changes in elemental content in fronds of Azolla filiculoides due to arsenic accumulation

This study analyzed the accumulation of arsenic and its influence on the content of P, Mn, Fe, Cu, Zn, S, Ca, Cl, and K in fronds of Azolla filiculoides via X-ray fluorescence (XRF). Azolla was exposed to increased concentrations of sodium arsenate (0, 5, 10, 20, and 30 μg ml ^? 1) in Yoshida's nutrient solution. After 96 h, fronds were collected and taken to constant weight to calculate the relative growth rate (RGR), the biomass duplication rate, the bioaccumulation factor (BAF), and the elemental concentration via XRF analysis. By increasing As concentrations the RGR and BAF were reduced. The greatest accumulation of As in fronds was achieved at 20 μg As ml ^? 1, which did not show significant differences with the highest concentration. Accumulation of As in fronds diminished concentrations of Mn, Fe, Zn, S, Ca, and K, while the concentration of P remained low but unchanging. The P content was significantly lower than the As content, thus the As:P ratio in fronds enhanced as the As concentration increased. Concentrations of Cl and Cu were unaffected due to As. This is one of the first reports about the influence of As-accumulation on the elemental content in Azolla fronds.     

Rapid Shedding of Roots from Azolla filiculoides Plants in Response to Inhibitors of Respiration

Chemicals that are known to be inhibitors of respiration, namely,sodium azide, sodium cyanide, DNP, CCCP and DCCD, caused sheddingof roots of Azolla filiculoides plants. Complete shedding ofroots of more than 10 mm in length occurred when Azolla plantswere treated with sodium azide, DNP or CCCP at concentrationsabove 50µM, 30µM and 20µM, respectively. Theshedding in response to sodium azide, DNP and CCCP was veryrapid and was complete within 5–20 min. Microscopic studies revealed the presence of large cells atthe outer surface of the base of roots that were about to beshed. The tested-chemicals caused the expansion, rounding upand separation of these cells, probably via the rapid absorptionof water, with resultant shedding of roots. When detached roots were immersed in a solution of sodium azide,DNP or CCCP, the large cells expanded and rounded up. Thesecells were gradually separated from the roots. However, theseparation of the cells caused by DNP was inhibited by the presenceof various buffers at acidic pH. By contrast, buffers at neutralpH greatly facilitated the separation of cells irrespectiveof whether DNP was present or absent. The results suggest that the separation of cells involves anincrease in the pH of the external solution in the vicinityof the large cells. A change in ion fluxes of the large cells,which accompanies an increase in pH of the external solution,may cause the rapid absorption of water by the cells and resultin the expansion and separation of the cells. (Received June 15, 1993; Accepted October 25, 1993)     

新疆引种蕨状满江红的生态适应性及生物学功能初探

结合新疆的环境特点,对蕨状满江红（Azolla filiculoides Lam.）进行了一系列引种适应性试验和生物学功能测定。结果表明：蕨状满江红在新疆有很强的适应性,在5-40℃均能生长,其生长最适温度为℃,且耐低温;在2-8g/L的盐溶液及pH4-10范围内也能生长,并且可降低水体的矿化度及pH值;具有净化养殖水体和很强的富钾能力,植株钾含量最高可达干重的9.66％;水利用率高,并能有效减少养殖水体表面的蒸发,有保水作用。在新疆的河、湖和水库适量养殖蕨状满江红,可实现其生态与经济价值。     

Hydrolytic activity of bovine tryptophanyl-tRNA-synthetase cause by removal of Zn2+

Bovine tryptophanyl-tRNA synthetase (E.C.6.1.1.2) lacking Zn2+ ions removed by chelation with phosphonate analog of P1,P4-bis-(5'-adenosyl)tetraphosphate (Ap4A) was obtained (E-Zn). E-Zn lost the ability to form tryptophanyl adenylate, however it hydrolyses ATP to ADP and further on to AMP and Pi. GTP serves as a substrate with Km approximately 0.6 mM. It is proposed that the hydrolysable nucleotides bind to a nucleotide binding site(s) distinguishable from the substrate (catalytic) ones. After incubation of E-Zn with Zn2+ and Mg2+ the initial catalytic activity (ATP-PPi exchange and amino-acylation reactions) is restored whereas the hydrolytic activity becomes fully suppressed.     

Removal of lead from solution by the non-viable biomass of the water fern Azolla filiculoides

Non-viable biomass of the aquatic fern, Azolla filiculoides, removed up to 93 mg lead/g biomass from solution. Lead removal varied from 30% of the initial lead concentration at pH 1.5 to approximately 95% at pH values of 3.5 and 4.5. Lead removal decreased to 30% of the initial lead concentration if the lead concentration was initially over 400 mg/l. Lead removal remained at approximately 90% between 10 °C and 50 °C. Biomass concentration (4–8 mg/l) had little effect on lead removal. © Rapid Science Ltd. 1998