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.     

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。     

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.     

Differential response ofAzolla microphylla kaulf. andAzolla filiculoides Lam. to sodium fluoride

We assessed the differential response ofAzolla microphylla andAzolla filiculoides to fluoride stress by growing them in culture media containing 1 to 50 ppm sodium fluoride (NaF).A microphylla had a higher total chlorophyll content thanA. filiculoides. Both species showed gradual decreases in protein content as the concentration of NaF increased.A. microphylla accumulated less proline thanA. filiculoides when more NaF was added to the culture medium. For all concentrations tested, the amount of residual fluoride in the nutrient media that supportedA. microphylla was higher than in the nutrient media used for growingA. filiculoides.     

Differential responses ofAzolla microphylla Kaulf andAzolla filiculoides Lam. to lead nitrate

The aquatic fernAzolla is used as a green manure for rice production systems in warm temperate and tropical regions throughout the world. We used lead nitrate in nutrient media to assess the tolerance/response of twoAzolla microphylla andAzolla filiculoides to heavy metals. While both species showed negative responses in growth with an increase in lead concentrations, They were distinctly different in their tolerance for higher concentration of the heavy metal. This was apparent in their growth and biochemical characteristics. Amicrophylla was more tolerant of the higher concentrations of lead nitrate (25 and 50 ppm), whereasA. filiculoides had a higher rate of lead uptake.     

POTENTIAL OF THE AQUATIC FERN AZOLLA FILICULOIDES IN BIODEGRADATION OF AN AZO DYE: MODELING OF EXPERIMENTAL RESULTS BY ARTIFICIAL NEURAL NETWORKS

The potential of an aquatic fern, Azolla filiculoides, in phytoremediation of a mono azo dye solution, C.I. Acid Blue 92 (AB92), was studied. The effects of operational parameters such as reaction time, initial dye concentration, fern fresh weight, pH, temperature and reusability of the fern on biodegradation efficiency were investigated. The intermediate compounds produced by biodegradation process were analyzed using GC–MS analysis. An artificial neural network (ANN) model was developed to predict the biodegradation efficiency. The findings indicated that ANN provides reasonable predictive performance (R² = 0.961). The effects of AB92 solutions (10 and 20 mg L^?1) on growth, chlorophylls and carotenoids content, activity of antioxidant enzymes such as superoxide dismutase, peroxidase and catalase and formation of malondialdehyde were analyzed. AB92 generally showed inhibitory effects on the growth. Moreover, photosynthetic pigments in the fronds significantly decreased in the treatments. An increase was detected for lipid peroxidation and antioxidant enzymes activity, suggesting that AB92 caused reactive oxygen species production in Azolla fronds, which were scavenged by induced activities of antioxidant enzymes.     

Production potential of aquatic plants in systems mixing floating and submerged macrophytes

1. To investigate whether the areal production of aquatic plant systems can be increased by growing floating and submerged plants together, the floating fern Azolla filiculoides was grown at six densities and two nutrient availabilities in the presence and absence of the submerged macrophyte Elodea canadensis .
2. High nutrient availability did not affect the total areal biomass production, but raised the internal N concentration of Azolla and Elodea by 34% and 152%, respectively, and the internal P concentration by 50% and 378%.
3. High Azolla density reduced Elodea production, whereas Elodea did not affect the production of Azolla . A maximal total production of 4.0 g DW m⁻² day⁻¹ was obtained at an Azolla density at and above full surface cover, when Elodea contribute with less than 10% to the total. This contribution did not raise the combined production of Azolla and Elodea significantly above the production of Azolla grown alone. Thus, maximum production was not enhanced by growing floating and submerged macrophytes together.     

北方农家屋顶养绿萍技术及生态经济效益

北方农家屋顶养绿萍技术及生态经济效益安淑苹（中国科学院石家庄农业现代化研究所,０５００２１）ＴｈｅＥｃｏｌｏｇｉｃａｌａｎｄＥｃｏｎｏｍｉｃａｌＢｅｎｅｆｉｔｓｏｆＣｕｌｔｉｖａｔｉｎｇＡｚｏｌａｆｉｌｉｃｕｌｏｉｄｅｓｏｎｔｈｅＲｏｏｆｔｏｐｉｎｔ...     

Volatile compounds from the symbiotic system Azolla filiculoides‐Anabaena azollae bacteria

Abstract

Azolla filiculoides is an aquatic pteridophyte that may be used as animal food, biofertilizer and phytoremediation. Its volatile composition was never studied although several phytochemical analyses were performed. The volatile composition of A. filiculoides grown outdoors in a pond at the Botanical Garden of Lisbon University (BGLU) or in culture conditions as well as the effect of different harvesting times and the storage type were evaluated. The volatiles isolated by hydrodistillation and distillation‐extraction were analysed by gas chromatography and gas chromatography‐mass spectrometry. The oil of all the A. filiculoides samples studied affords a yellowish colour and an unpleasant odour in a yield of 0.01% (v/fw). Alcohols, aldehydes, alkanes and ketones dominated the culture samples, while aldehydes, alcohols, terpenoids and alkanes represented the main volatiles of the BGLU samples. Some quantitative differences were detected in seasonal and type of storage (fresh, dry or frozen at ?20°C) studies of A. filiculoides from the BGLU. The BGLU and culture volatiles showed qualitative differences: 2‐ethyl‐1‐hexanol was only identified in the fern culture, whereas acetophenone, pentylfuran, acetylpyridine and 2‐octanone were only detected in BGLU samples. The dendrogram showed two distinct clusters (culture and BGLU samples). The possible biological origin and bioactivity of some of the volatile compounds is discussed.

Abbreviations: FID, flame ionization detector; i.d., internal diameter; v/fw, volume by fresh weight; GC, gas chromatography; GC‐MS, gas chromatography‐mass spectrometry; u, unified atomic mass unit     

Testa sculpture in the genus Frailea (Cactaceae)

The primary sculpture of the seed surface in the genus Frailea (Cactaceae) is characterized by a i flat outer periclinal wall and the presence of an usually eccentric papilla. Papilla morphology differs mainly in size and breadth:length ratio. Seeds of different species (groups) are characterized by special patterns in the arrangement of short and long papillae on the surface, thus providing a useful tool for taxonomic studies in Frailea. The seeds of Frailea castanea possess branched papillae, a character restricted in this genus to this species. Moreover, such papilla morphology seems to be unique for the seed epidermis in spermatophytes. The possible function of the papillae is discussed.     

Proteomic analysis of the cyanobacterium of the Azolla symbiosis: identity, adaptation, and NifH modification

Cyanobacteria are able to form stable nitrogen-fixing symbioseswith diverse eukaryotes. To extend our understanding of adaptationsimposed by plant hosts, two-dimensional gel electrophoresisand mass spectrometry (MS) were used for comparative proteinexpression profiling of a cyanobacterium (cyanobiont) dwellingin leaf cavities of the water-fern Azolla filiculoides. Homology-basedprotein identification using peptide mass fingerprinting [matrix-assistedlaser desorption ionization-time of flight (MALDI-TOF-MS)],tandem MS analyses, and sequence homology searches resultedin an identification success rate of 79% of proteins analysedin the unsequenced cyanobiont. Compared with a free-living strain,processes related to energy production, nitrogen and carbonmetabolism, and stress-related functions were up-regulated inthe cyanobiont while photosynthesis and metabolic turnover rateswere down-regulated, stressing a slow heterotrophic mode ofgrowth, as well as high heterocyst frequencies and nitrogen-fixingcapacities. The first molecular data set on the nature of theNifH post-translational modification in cyanobacteria was alsoobtained: peptide mass spectra of the protein demonstrated thepresence of a 300–400 Da protein modification localizedto a specific 13 amino acid sequence, within the part of theprotein that is ADP-ribosylated in other bacteria and closeto the active site of nitrogenase. Furthermore, the distributionof the highest scoring database hits for the identified proteinspoints to the possibility of using proteomic data in taxonomy. Key words: Azolla, cyanobacteria, NifH modification, proteomics, symbiosis, taxonomy Received 24 June 2007; Revised 21 October 2007 Accepted 22 October 2007     

黄芪复合体(豆科)核型资料的聚类分析

在平均欧氏距离系数基础上,运用UPGMA法,对黄芪复合体5个类群11个居群的核型资料进行了Q型聚类分析,结果表明,膜荚黄芪Astragalus membranaceus和A. penduliflorus的不同居群在核型上存在明显的差异,但二者之间以及它们与民和黄芪、淡紫花黄芪的居群之间具有一定的连续性。蒙古黄芪在核型上与其它类群均存在一定的差异,且存在明显的间断。因此,本文作者认为:A. penduliflorus应视为膜荚黄芪的异名,黄芪复合体应包括2种:膜荚黄芪(A. membranaceus(Fisch)Bunge)和蒙古黄芪(A. monghulicus Bunge)、2亚种:膜荚黄芪(A. membranaceus spp. membranaceus)、民和黄芪(A. membranaceus spp. minhensis)和1变种:淡紫花黄芪(A. membranaceus var. purpurinus Y.C.Ho)。黄芪复合体核型的进化趋势是从对称向不对称发展,与Stebbins的观点一致。