Use of Azolla as a test organism in a growth chamber of simple design

Summary The construction and application of a new type of growth chamber, in which different growth conditionsi.e.: temperature, humidity, pH, light intensity, light colour, change in nutrient composition and gas exchange can easily be controlled, are presented. The method has previously been applied to twoAzolla speciesviz. Azolla filiculoides, which is cold tolerant andAzolla pinnata (distinguished in Vietnam as the form Xanh), which is heat tolerant. In the growth chamber natural growth conditions of the Azolla —Anabaena azollae symbiotic association were imitated as much as possible. For testing the system, methods discussed earlier^8,14 and some previously presented data, concerning photosynthetic activities, such as oxygen evolution and nitrogen fixation (acetylene reduction) of twoAzolla species³⁹, were partially used. Biomass ofA. filiculoides was measured and reactions to its environment at conditions when grown in the field and in the growth chamber, were studied. Growth and photosynthesis measurements were performed under special light conditions and with whole plants grown under laboratory conditions. Anthocyanin synthesis was studied in relation with humidity. Anthocyanin spectra were analyzed by means of a spectrum-deconvolution method. On leave from the Department of Plant Physiology of the University of Hanoi, Vietnam.     

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     

Phylogenetic study of rhizobia nodulating pea (Pisum sativum) isolated from different geographic locations in Tunisia

Nodulated Pisum sativum plants showed the presence of native rhizobia in 16 out of 23 soil samples collected especially in northern and central Tunisia. A total of 130 bacterial strains were selected and three different ribotypes were revealed after PCR-RFLP analysis. Sequence analyses of rrs and four housekeeping genes (recA, atpD, dnaK and glnII) assigned 35 isolates to Rhizobium laguerreae, R. ruizarguesonis, Agrobacterium radiobacter, Ensifer meliloti and two putative genospecies. R. laguerreae was the most dominant species nodulating P. sativum with 63%. The isolates 21PS7 and 21PS15 were assigned to R. ruizarguesonis, and this is the first report of this species in Tunisia. Two putative new lineages were identified, since strains 25PS6, 10PS4 and 12PS15 clustered distinctly from known rhizobia species but within the R. leguminosarum complex (Rlc) with the most closely related species being R. indicum with 96.4% sequence identity. Similarly, strains 16PS2, 3PS9 and 3PS18 showed 97.4% and 97.6% similarity with R. sophorae and R. laguerreae, respectively. Based on 16S-23S intergenic spacer (IGS) fingerprinting, there was no clear association between the strains and their geographic locations. According to nodC and nodA phylogenies, strains of Rlc species and, interestingly, strain 8PS18 identified as E. meliloti, harbored the symbiotic genes of symbiovar viciae and clustered in two different clades showing heterogeneity within the symbiovar. All these strains nodulated and fixed nitrogen with pea plants. However, the strains belonging to A. radiobacter and the two remaining strains of E. meliloti were unable to nodulate P. sativum, suggesting that they were non-symbiotic strains. The results of this study further suggest that the Tunisian Rhizobium community is more diverse than previously reported.     

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.     

强光及高温诱发白化的中国绿水螅共生细菌多样性的特征

目的：探究强光及高温诱发白化的中国绿水螅共生细菌多样性的特征。方法：以光照强度2000 Lux和温度25℃条件为对照,分别在强光胁迫（6000 Lux,25℃）、高温胁迫（2000 Lux,33℃）以及强光和高温联合胁迫（6000 Lux,33℃）等3种条件下进行诱导中国绿水螅白化的实验。白化实验进行到21天后,采用对单个水螅细胞中的共生藻进行计数的方法检测绿水螅白化的程度,同时通过16S r DNA高通量测序的方法分析绿水螅共生细菌多样性及丰度变化。结果：在强光胁迫、高温胁迫及强光和高温联合胁迫下绿水螅体内共生藻数量均显著减少（P<0.05）。强光胁迫下绿水螅共生细菌中蓝细菌门（Cyanobacteria）的丰度上升,而在强光和高温联合胁迫下绿水螅共生细菌中不但蓝细菌门的丰度上升,绿硫菌门（Chlorobi）的丰度也明显提高。此外,KEGG富集分析结果表明发生白化的绿水螅共生细菌与亚油酸、类胡萝卜素及甜菜红色素等抗氧化剂的合成和代谢相关。结论：蓝细菌和绿硫菌的光合作用产物有可能被水螅宿主所利用、以弥补水螅宿主由于共生藻的减少带来的营养缺乏;强光和高温胁迫下绿水螅出现白化现象后共...     

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。     

Lentil (Lens culinaris Medik.) nodulates with genotypically and phenotypically diverse rhizobia in Ethiopian soils

Forty-eight lentil-nodulating rhizobia were isolated from soil samples collected from diverse agro-ecological locations in Ethiopia, and characterized based on 76 phenotypic traits. Furthermore, 26 representative strains were selected and characterized using multilocus sequence analyses (MLSA) of core (16S rRNA, recA, atpD, glnII and gyrB) and symbiotic (nodA and nifH) genes. Numerical analysis of phenotypic characteristics showed that the 48 test strains fell into three major distinct clusters. The phylogenetic trees based on 16S rRNA genes showed that they belong to the Rhizobium genus. Our phylogenetic reconstruction based on combined gene trees (recA, atpD and glnII) supported three distinct sub-lineages (Clades I–III). While genospecies I and II could be classified with Rhizobium etli and Rhizobium leguminosarum, respectively, genospecies III, might be an unnamed genospecies within the genus Rhizobium. Phylogenetic reconstruction based on the symbiosis-related genes supported a single cluster, indicating differences in the evolutionary histories between chromosomal and symbiotic genes. Overall, these results confirmed the presence of a great diversity of lentil-nodulating Rhizobium species in Ethiopia, inviting further exploration. Moreover, the differences in symbiotic effectiveness of the test strains indicated the potential for selecting and using them as inoculants to improve the productivity of lentil in the country.     

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。     

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