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     

Immunocytochemical localization of nitrogenase in bacteria symbiotically associated with Azolla spp.

In situ immunogold labeling and transmission electron microscopy were used to detect nitrogenase in bacteria (bactobionts) symbiotically associated with leaf cavities of Azolla caroliniana and Azolla filiculoides. In A. caroliniana, the Fe protein of the nitrogenase complex was detected in a subset of the distinct bactobiont types present in leaf cavities of all ages. Similar results were obtained for the bactobionts of A. filiculoides with antisera against both the Fe and MoFe subunits of nitrogenase.     

Immunocytochemical localization of nitrogenase in bacteria symbiotically associated with Azolla spp.

In situ immunogold labeling and transmission electron microscopy were used to detect nitrogenase in bacteria (bactobionts) symbiotically associated with leaf cavities of Azolla caroliniana and Azolla filiculoides. In A. caroliniana, the Fe protein of the nitrogenase complex was detected in a subset of the distinct bactobiont types present in leaf cavities of all ages. Similar results were obtained for the bactobionts of A. filiculoides with antisera against both the Fe and MoFe subunits of nitrogenase.     

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...     

Genetic diversity among and within cultured cyanobionts of diverse species of <Emphasis Type="Italic">Azolla</Emphasis>

The cyanobionts isolated from 10 Azolla accessions belonging to 6 species (Azolla mexicana, A. microphylla, A. rubra, A. caroliniana, A. filiculoides, A. pinnata) were cultured under laboratory conditions and analyzed on the basis of whole cell protein profiles and molecular marker dataset generated using repeat sequence primers (STRR(mod) and HipTG). The biochemical and molecular marker profiles of the cyanobionts were compared with those of the free-living cyanobacteria and symbiotic Nostoc strains from Anthoceros sp., Cycas sp. and Gunnera monoika. Cluster analysis revealed the genetic diversity among the selected strains, and identified 3 distinct clusters. Group 1 included cyanobionts from all the 10 accessions of Azolla, group 2 comprised all the symbiotic Nostoc strains, while group 3 included the free-living cyanobacteria belonging to the genera Nostoc and Anabaena. The interrelationships among the Azolla cyanobionts were further revealed by principal component analysis. Cyanobionts from A. caroliniana-A. microphylla grouped together while cyanobionts associated with A. mexicana-A. filiculoides along with A. pinnata formed another group. A. rubra cyanobionts had intermediate relationship with both the subgroups. This is the first study analyzing the diversity existing among the cultured cyanobionts of diverse Azolla species through the use of biochemical and molecular profiles and also the genetic distinctness of these free-living cyanobionts as compared to cyanobacterial strains of the genera Anabaena and Nostoc.     

温度对三种满江红光合及固氮活性的影响

本文报道满江红(Azolla imbricata)、卡洲满江红(A. caroliniana)和蕨状满江红(A. filiculoides)的光合与固氮(乙炔还原)活性对温度的反应差异。根区培养液温度在7—40℃范围内满江红与卡洲满江红的光合活性在30℃达到峰值,高于或低于30℃均急剧下降。而蕨状满江红在7—25℃的根区温度范围内光合活性差异不大,高于25℃则下降(图2)。0℃24小时或40℃2小时暗预处理对三种满江红光合活性与乙炔还原活性表现出不同影响(图3,4)。本文报道的方法可用于满江红生理生态参量的比较研究。     

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.     

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.     

Azolla filiculoides Nitrogenase Activity Decrease Induced by Inoculation with Chlamydomonas sp

Experiments were conducted to determine the influence of Chlamydomonas sp. on nitrogen fixation (C(2)H(2) --> C(2)H(4)) in Azolla filiculoides and on the nitrogen fixation and growth of free-living Anabaena azollae 2B organisms. Inoculation of azolla medium with Chlamydomonas sp. was associated with decreased nitrogenase activity in A. filiculoides and with increases in the density of a fungal population identified as Acremonium sp. Subsequent inoculation of azolla medium with this fungus was also accompanied by a significant decrease in nitrogenase activity of A. filiculoides. However, the extent of depression of nitrogenase activity was significantly higher when azolla medium was inoculated with Chlamydomonas sp. than when it was inoculated with Acremonium sp. Inoculation of nitrogen-free Stanier medium with either Acremonium sp. or Chlamydomonas sp. did not adversely affect the growth or nitrogenase activity of free-living A. azollae. Decreased nitrogenase activity in A. filiculoides is apparently related to the adverse influence of the green alga and the fungus on the macrosymbiont. The mechanisms that might be involved are discussed.     

Life history and laboratory host range of Stenopelmus rufinasus, a natural enemy for Azolla filiculoides in South Africa

The frond-feeding weevil, Stenopelmus rufinasus Gyllenhal, was imported into quarantine for testing as a potential natural enemy for the invasive fern Azolla filiculoides Lamarck in South Africa. Adult S. rufinasus lived for approximately 55 days during which the females produced on average 325 offspring. The developmental period for the immature stages (egg, three larval instars and pupation) was about 20 days indicating the potential for several overlapping generations per year. Both the adults and the larvae caused severe damage to A. filiculoides in the laboratory. Host specificity of this insect was determined by adult no-choice oviposition and larval starvation tests on 31 plant species in 19 families. Adult feeding, oviposition and larval development was only recorded on the Azolla species tested (A. filiculoides, A. pinnata subsp. poss. asiatica R.K.M. Saunders and K. Fowler, A. pinnata subsp. africana (Desv.) R.K.M. Saunders and K. Fowler and A. nilotica De Caisne Ex Mett.). A. filiculoides proved to be significantly the most suitable host for the weevil. The low adult emergence from A. nilotica and A. pinnata subsp. africana would most probably prevent the weevil from establishing on them in the field. A. pinnata subsp. poss. asiatica which supported greater development, is thought to be introduced and has a weedy phenology in South Africa and is thus of low conservation value. Therefore, any damage inflicted on this plant in the field may be an acceptable trade-off for the predicted impact of S. rufinasus on the aggressive exotic weed, A. filiculoides.     

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.     

A Non segregation F2 Population Derived from the Cross of Triploid×Diploid in Rice

A non-segregating F2 population was obtained from the cross of tfiploid × diploid in rice ( Oryza sativa L. ). The maternal parent used in cross was SAR-3 which is an autotriploid occurring in the field, and the paternal was a restored line Sheng 47. The F2 population from the same F1 plant appears uniform, and so does F3. Results from coefficients of variation (CV) of F2, Ducan’s test of F3 and SSRs marker analysis showed that the F2 of SAR-3 × Sheng 47 was non-segregating. Markers for either parent could be present in F2 progenies. In some cases, both markers for each parent could be found on one chromosome. The authors presume that after crossing there might be recombination of chromosome followed by homozygotization. Stability of early generation could be utilized in breeding, as it is a new approach to shorten the breeding procedures.     

Identification of a common cyanobacterial symbiont associated with Azolla spp. through molecular and morphological characterization of free-living and symbiotic cyanobacteria.

Symbiotically associated cyanobacteria from Azolla mexicana and Azolla pinnata were isolated and cultured in a free-living state. Morphological analyses revealed differences between the free-living isolates and their symbiotic counterparts, as did restriction fragment length polymorphism (RFLP) analyses with both single-copy glnA and rbcS gene probes and a multicopy psbA gene probe. RFLP analyses with Anabaena sp. strain PCC 7120 nifD excision element probes, including an xisA gene probe, detected homologous sequences in DNA extracted from the free-living isolates. Sequences homologous to these probes were not detected in DNA from the symbiotically associated cyanobacteria. These analyses indicated that the isolates were not identical to the major cyanobacterial symbiont species residing in leaf cavities of Azolla spp. Nevertheless, striking similarities between several free-living isolates were observed. In every instance, the isolate from A. pinnata displayed banding patterns virtually identical to those of free-living cultures previously isolated from Azolla caroliniana and Azolla filiculoides. These results suggest the ubiquitous presence of a culturable minor cyanobacterial symbiont in at least three species of Azolla.     

Studies on cadmium localization in the water fern Azolla

Uptake of cadmium by the water fern Azolla filiculoides (Lamarck) was characterized, and the localization of the metal in the roots and shoots as well as its effects on some essential elements were studied. Cadmium was accumulated at a rapid rate in Azolla plants within 1 h and then more gradually up to 77 h. Cadmium content was increased in the inner epidermis, cortex and bundle cell walls of the root between 33 and 77 h. This accumulation was characterized by the appearance of small dark grains with high content of cadmium, phosphate and calcium along the epidermal cells. The shoots of Azolla plants grown in the presence of cadmium showed high content of cadmium only in the ventral lobe submerged in the growth medium, suggesting that cadmium was absorbed directly from the medium. The effect of cadmium on essential elements in Azolla was characterized by simultaneous increases in calcium and cadmium content in the root and shoot and by decreases in magnesium content in the root and potassium content in the shoot.     

Identification of a common cyanobacterial symbiont associated with Azolla spp. through molecular and morphological characterization of free-living and symbiotic cyanobacteria.

Symbiotically associated cyanobacteria from Azolla mexicana and Azolla pinnata were isolated and cultured in a free-living state. Morphological analyses revealed differences between the free-living isolates and their symbiotic counterparts, as did restriction fragment length polymorphism (RFLP) analyses with both single-copy glnA and rbcS gene probes and a multicopy psbA gene probe. RFLP analyses with Anabaena sp. strain PCC 7120 nifD excision element probes, including an xisA gene probe, detected homologous sequences in DNA extracted from the free-living isolates. Sequences homologous to these probes were not detected in DNA from the symbiotically associated cyanobacteria. These analyses indicated that the isolates were not identical to the major cyanobacterial symbiont species residing in leaf cavities of Azolla spp. Nevertheless, striking similarities between several free-living isolates were observed. In every instance, the isolate from A. pinnata displayed banding patterns virtually identical to those of free-living cultures previously isolated from Azolla caroliniana and Azolla filiculoides. These results suggest the ubiquitous presence of a culturable minor cyanobacterial symbiont in at least three species of Azolla.     

Indole-3-acetic acid (IAA) production by Arthrobacter species isolated from Azolla.

Arthrobacter species, isolated from the leaf cavities and the microsporocarps of the aquatic fern species Azolla pinnata and Azolla filiculoides, produced indole-3-acetic acid (IAA) in culture when the precursor tryptophan was added to the medium. No IAA production was detected in the absence of tryptophan. Maximum IAA formation was obtained in the first 2 d of incubation. Part of the tryptophan was transformed to N alpha-acetyl-L-tryptophan.     

小麦的不同染色体组对G、S~v、D~2、M~u型细胞质“中国春”育性的影响

本文以Ｇ、Ｊｖ、Ｄ２、Ｍｕ型异细胞质“中国春”;小麦为母本与１１个不同染色体组类型小麦为父本进行杂交,观察当代的结实率,Ｆ１的育性与性状的变化、减数分裂行为,进一步探讨小麦的细胞质雄性不育与染色体组类型的关系。结果表明：当代结实率主要由父本染色体组类型决定,Ｆ１的育性表现十分复杂,同一父本与不同的异细胞质“中国春”杂交,有的表现可育,有的表现不育,细胞质有一定的影响。Ｆ１的性状,有的与细胞质类型有关,如熟期、雄蕊形态、生长期与抗病性等。选择适宜可获得有明显杂种优势的组合。有的细胞质类型可影响减数分裂行为使中期Ⅰ配对的染色体增加或减少,在四分期出现微核与异常四分孢子。     

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.