细叶满江红大孢子果的扫描电镜观察

细叶满江红(Azolla filicufoides Lam.)是优良的水生绿肥和饲料作物,又是用孢子果越夏和过冬的好材料,植物学者对其进行广泛研究已有悠久的历史。本文记述了电镜扫描观察到的大孢子果及小孢子囊泡胶块的图象;认为大孢子果表面同小孢子囊泡胶块的附着力,与大孢子果的萌发力有相关性;指出孢子果带菌,将是导致高温季节大田满江红发生毁灭性病害“自然倒萍”的主要因素之一。     

无藻萍的RAPD分析及其在三膘组满江红种间关系研究中的应用

从满江红Azolla Lam.萍-藻共生体中提取DNA进行的RAPD系统分析通常忽视了满江红样品的异质性。本研究通过获得无藻的满江红,比较有藻萍、无藻萍和离体藻之间的RAPD指纹图谱。发现从有藻萍中提取DNA的扩增反应来源于萍藻双方DNA的共同影响。依引物和植物样本的不同,共生双方对扩增产物的贡献结果不同,说明了用无藻萍进行RAPD检测的重要性。对满江红三膘组5个种的11个无藻萍样本进行了RAPD分析,由9个引物产生的127个DNA多态片段用于计算样本间的Jaccard相似系数和UPGMA树状聚类图。结果     

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.     

Effect of phosphorus on Azolla and its utilization in rice culture in Niger

The trials to use Azolla as a green manure for rice culture were made in the Niger basin.Azolla pinnata (Niger isolate) was used for the experiments. The effect of phosphorus on the growth and N₂-fixation was examined in the field and in the laboratory. The growth rate and N content were maximum with P 3.1 ppm culture solution under laboratory conditions. The threshold P content for the growth was 0.5–0.6% in the dry matter. Maximum N content was 4.1% in the laboratory culture. In the field culture, the effect of P fertilizer on the growth and N yield of Azolla was tested. The split application of 6.5 kg P ha⁻¹ per 13 days was most effective in stimulating the growth of Azolla. One kg of P as triple superphosphate produced 3.66 kg N in the Azolla. Maximum growth rate and N content in the field trials was 4.3 days (doubling time) and 2.3%, respectively. The lower productivity in the field in comparison with the laboratory culture was considered to be due to higher temperature and light intensity. the growth of Azolla was suppressed in the hot season in the Niger basin. The growth rate and N content were reduced during the high temperature period over 30°C on an average. The effect of inoculation of Azolla on rice yield was tested in the field experiment. The grain yield was increased 27% by Azolla incolation over the treatment without Azolla inoculation in — N fertilizer treatments. While the growth of Azolla with rice plants did not attain saturated density (1.8 kg fresh weight m⁻²), the effect on the grain yield was comparable to 40 kg N ha⁻¹ as urea.     

Electron Microscopic Observation of the Azolla-Anabaena azollae Relationship

The structure of Azolla pinnate leaves was examined by means of light and transmission electron microscopy. Emphasis was put on the ultra structural cytology of leaf cavity hairs both in association with Anabaena and in Anabaena-free cultures of Azolla and on the roles of the hair in substance change between the symbionts. The cavity hairs were multicultural and branched. There were numerous mitochondria, plastids, endoplasmic reticular and ribosome’s in the cytoplasm of the hair. A. marked characteristic of the hair was the cell wall ingrowths; There were large electron-transparent area between the in growing cell wall and the plasmolemma. Some vesicles were found in this area. It was suggested that these vesicles as transporters played the role in transporting substances. Electron microscopy revealed that some differences were present between the basal cell and the terminal branched cell of the hairs. In the latter, the cytoplasma, organelles, growing wall and vesicles were richer in the electron-transparent area than in the former This feature of the terminal branched cell showed that the terminal cell of the hair was more active in absorption and/or secretion of metabolites than that of the basal cell. Some hairs were found near the stem apex of Azolla. It was suggested that these hairs functioned in supplying the nitric compounds for the algae living on the stem apex of Azolla. These algae had no ability to fix nitrogen because of lacking heterocyst. In the absence of Anabaena azollae, the leaf cavity hairs were still present in Azolla pinnata. However, a lot of osmiophilic substances can often be seen in the vacuole of this hair.     

Scanning Electron Microscopic Observation of Symbiotic Relationship of Azolla-Anabaena AzoUae During the Vegetative Growth

The occurrence and development of the hair ceils on the shoot tips and in the leaf cavities of A. filiculoides, A. microphylla, A. pinnata and their algae-free cultures were examined by means of scanning electron microscopy with microdissect technique. The patterns of Anabacna moving into the leave cavities from the shoot tips were investigated on three species of Azolla during their vegetative growth. The results showed that the patterns of symbiotic Anabaena infecting the leaf cavities are similarity among three species of Azolla and may be divided to the four phases which are summarized as follows: 1. occurrence of primary branched hair and adhesion of Anabaena; 2. development of primary branched hair and spreding of Anabaena; 3. building of hair bridge and entrance of Anabaena into the cavities; 4. formation of secondary simple hair and transference of Anabaena within the cavity. These observations resulted in a hypothesis that hair induces and leads its partner. It is suggested that the hair cell is likely to be a structure of Azolla for attracting and recognizing its symbiont in addition to transport substance between fern and algae.     

The Development of Microsporangium and Microspore in Azolla

This paper presents a detailed report on the developmental progresses of the microsporangium and its microspores in Azolla filiculoides Lam., and shows the morphologicaI structures of the respective developmental stares with the aid of scanning electron photographs. The entire developmental progress may be divided into six stages: ( 1 ) The microspore mother cell initiating stage The microsporangium initial on the placenta of the sporocarp gave rise a sporogenous cell, and then divided four times to form sixteen microspore mother cells; (2) The meiotic stage–The microspore mother cells initiated meiosis inside their calIose walls. The radial and inner tangential walls of the tapetum were dissolved at the same time and followed by the formation of a sporoplasmodium; (3) The microspore shrinking Ⅰ–After the callose walls of tetrads was dissolved, those microspores that just released from the callose walls shrunk intensely and became spherical later again. The sporoderm of microspores was principally synthesized in this stage, and the volume of microspores became evidently increased. The microspores then gradually moved to the periphery of the sporoplasmodium; (4) The microspore shrinking Ⅱ-Each microspore formed a large vacuole and gave rise the second contraction. The periphery of the sporoplasmodium was gradually dissolved; (5) The massulae forming stage–The sporoplasmodium was dissolved successivelly, and the undissolvable granules and organelle membrane residues. became aggregated into the compartmental layer, and the microsporangium was divided into several large vesicles, each vesicle will form a massulae; (6) The microspore germinating stage–The ,natured microspores inside the massulae each gave rise an androgonial initial which divided two times to form four antherozoid mother cells and then gave rise the antherozoids. The relationships between the various morphological structures and their functions in the microsporangium developmental progress have breify discussed. In addition, our viewpoints have compared with those of previous investigations.     

An Autoradiographic Study of the Azolla-Anabaena azollae Relationship

The symbiotic relationships between Azolla and Anabaena azollae were studied by means of autoradiography after the Azolla was administered by 3H-thymidine, 3H-uridine, 3H-leucine and 3H-glucose. The experimental results showed that the four labeled compounds mentioned above were transfered from Azolla to Anabaena azollae through cavity hairs. This indicated that there was a transfer way of substances from fern to algae. It is suggested that the symbiotic relationship between Azolla and Anabaena azollae is more complicated than we have known up to now. The fern not only get the NH3 which was formed by symbiont-blue alga, but also supplied some nitrogen-containing substances, such as amino acids (or proteins), ribonucleotides for symbiotic algae. Although the symbiont still retained photosynthetic ability, the ability of nitrogen fixation might be developed and the photosynthetic autotrophic ability might be dropped gradually in the long symbiotic life and the Anabaena azolla needed take a portion of substances from the Azolla as replenishment.     

Are bacteria the third partner of theAzolla-Anabaena symbiosis?

The development of the prokaryotic colony inAzolla filiculoides indicates thatAnabaena azollae is maintained through the life cycle of the fern and present in the leaves and megasporocarps. The same biological pattern is applied to the bacteria that are also present in these structures and seems to follow a development pattern identical to the cyanobacteria and probably can be considered the third partner of this symbiotic association.     

不同光照条件下4种满江红(Azolla)品系体内多酚氧化酶活性的变化

在生物学观察测定基础上,引入生化测定方法探讨不同光照条件下卡洲满江红３００１ 、小叶满江红４０１８ 、杂交萍９０４６ 和回交萍ＭＨ３１ 四个红萍品系体内多酚氧化酶（ＰＰＯ） 活性变化趋势。结果表明,光照影响各满江红品系的生长速率与抗霉腐病能力,随着光照强度减弱,各品系的生长速率和抗霉腐病能力都下降。在低光下,供试的满江红品系生物量与体内ＰＰＯ 活性的相关性显著（ｒ＝ ０ ．９５６０） 。低光下满江红各品系生长速率、抗霉腐病能力和体内ＰＰＯ 活性的从高到低依次为卡洲满江红３００１ 、杂交萍９０４６ 、小叶满江红４０１８ 和回交萍ＭＨ３１ 。从生理、生化角度讨论了满江红耐荫性与体内多酚氧化酶活性的关系。     

满江红细胞质遗传和变异的初步研究

通过细绿萍（Ａｚｏｌｌａ ｆｉｌｉｃｕｌｏｉｄｅｓ）×小叶萍（Ａ．ｍ ｉｃｒｏｐｈｙｌｌａ）、细绿萍×墨西哥萍（Ａ．ｍ ｅｘｉｃａｎａ）种间,以及细绿萍×印度萍（Ａ．ｉｍ ｂｒｉｃａｔａ）亚属间正反交杂种Ｆ１ 代叶色变化,揭示杂种一代白化性状是母本细绿萍细胞质遗传的变异。电镜观察发现,白化苗质体结构异常,且淡绿苗组织细胞中含有正常叶绿体和异常质体。推测二者均可能和质体基因变异有关。不同杂交类型苗的白化程度和白化机率存在明显差异,且随着核基因变化呈现规律的变化。据此推测,白化性状也与核基因型密切相关     

满江红属系统学研究的新进展

本文从植物系统学角度对满江红属的研究进展作了全面综述,近年来从细胞水平提出了将满江红属重新划分为Azolla和Tetrasporocarpia2个亚属,经典的三膘（Azolla）和九膘（Rhizosperma)亚属作为新的Shbgen,Azolla中的2个组（Section）,而原有九膘亚属中的A.nilotica则为Subgen,Tetrasporocarpia的一个种,遗传育种和同工酶的研究证据对A.mexicana,A.microphylla和A.caroliniana能否在Sect.A-zolla中占据3个种的分类地位提出疑问,但要完全解决满江红属的系统学问题,分子生物学技术是重要手段,由于满江红为蕨－藻共生体,其样本的异质性影响了现有分子标记研究结果的可靠性。     

The taxonomy and distribution of Azolla species in southern Africa

The three Azolla species which occur in southern Africa, A. pinnata var. pinnata, A. nilotica and A. filiculoides are identified and their distributions illustrated. The endosymbiotic cyanobacterium Anabaena azollae occurred in dorsal leaf lobe cavities of all three species. The first two species are indigenous to southern Africa, whilst the third, A. filiculoides , is an introduced species from North America. Possible means whereby this species could have been introduced are discussed.     

The cyanobiont in an Azolla fern is neither Anabaena nor Nostoc

The cyanobacterial symbionts in the fern Azolla have generally been ascribed to either the Anabaena or Nostoc genera. By using comparisons of the sequences of the phycocyanin intergenic spacer and a fragment of the 16S rRNA, we found that the cyanobiont from an Azolla belongs to neither of these genera.     

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.     

Effects of sodium dodecyl sulphate on the aquatic macrophytes Azolla and Lemna

Abstract

In this work, we determined the tolerance to sodium dodecyl sulphate (SDS) of Azolla filiculoides and of Lemna minor. The presence of the detergent in the media affected growth more than the chlorophyll content. On the basis of the effect indices, Lemna is more tolerant to SDS than Azolla. The fern had a better capacity, compared with duckweed, to remove and accumulate the pollutant.     

Phytofiltration of anaerobically digested sugarcane ethanol stillage using a macrophyte with high potential for biofuel production

Anaerobically digested stillage (ADS) requires treatment before being discharged into water bodies or soils to avoid adverse effects. Phytofiltration systems are eco-friendly technologies for wastewater treatment, and they simultaneously serve as a source of biomass for biofuel production. The aim of the present study was to investigate the phytofiltration of ADS using Azolla sp. The effects of the ADS strength (dilutions 1:?50 and 1?:?25 v/v) and initial biomass density (IBD) [15.44 (IBD1) and 23.16 (IBD2) g dry weight (dw) m^?2] on plant growth and pollutant removal were assessed. Productivities obtained at ADS 1:?50 (2.93 and 3.04 g m^?2 d^?1 for IBD1 and IBD2, respectively) were not significantly different from those of a synthetic medium (2.56 and 3.15 g m^?2 for IBD1 and IBD2, respectively). Higher organic matter removal was found using ADS at 1:?25 than that obtained using ADS 1:?50 (52.16–53.34 vs 32.29–38.16%), while no IBD effect was observed. The nutrient concentrations in ADS were reduced significantly, especially the concentrations of NH₄-N (75.11–82.54%), PO₄-P (88.72–92.90%) and SO₄-S (55.95–66.61%). The conversion of nutrients from ADS into Azolla biomass may result in an effective way to produce an attractive feedstock for biofuel production.     

Azolla--a model organism for plant genomic studies

The aquatic ferns of the genus Azolla are nitrogen-fixing plants that have great potentials in agricultural production and environmental conservation. Azolla in many aspects is qualified to serve as a model organism for genomic studies because of its importance in agriculture, its unique position in plant evolution, its symbiotic relationship with the N2-fixing cyanobacterium, Anabaena azollae, and its moderate-sized genome. The goals of this genome project are not only to understand the biology of the Azolla genome to promote its applications in biological research and agriculture practice but also to gain critical insights about evolution of plant genomes. Together with the strategic and technical improvement as well as cost reduction of DNA sequencing, the deciphering of their genetic code is imminent.