野生植物根围的丛枝菌根真菌Ⅱ

本文主要报道了野生植物根围Glomus属的17个种,聚球囊霉G.aggregatumSchenck＆Smith,苏格兰球囊霉G.caledonium（Nicol.＆Gerd.）Trappe＆Gerd,近明球囊霉G．claroideumSchenck＆Smith,明球囊霉G．clarumNicolson＆Schenck,缩球囊霉G．constrictumTrappe,透光球囊霉G．diaphanumMorton,幼套球囊霉G．etunicatumBecker＆Gerdemann,集球囊霉G．fasciculatum（Thaxter）Gerd．＆Trappe,何氏球囊霉G．hoiBerch＆Trappe,地球囊霉G.geosporum（Nicol．＆Derd.）Warker,根内球囊霉G．intraradicesSchenck＆Smith,摩西球囊霉G．mosseae（Nicol．＆Gerd.）Gerd.＆Trappe,隐球囊霉G.occultumWalker,网状球囊霉G.reticulatumBhattcharjee＆Mukerji,地表球囊霉G.versiforme（Karsten）Berch,台湾球囊霉G．formosanumWu＆Chen,悬钩子球囊霉G．rubiformeGerdemann＆Trappe）Almeida＆Schenck;内养囊霉属1个种,稀有内养囊霉Entrophosporainfrequens（Hall）Ames＆Schenider。其中,网状球囊霉为我国新记录种。     

Family level inbreeding depression and the evolution of plant mating systems

Variation in the magnitude of inbreeding depression (ID) among families may have important consequences for mating system evolution. Experimental studies have shown that such variation is a common feature of natural plant populations. Unfortunately, the genetic and evolutionary significance of family level estimates remains obscure. Almost any kind of genetic variation will generate differences in ID among families, and as a consequence, a non-zero variance in family level ID is not sufficient to distinguish genetic architectures with wholly different implications for mating system evolution. Quantitative genetic methods provide a means to extract more information from ID experiments. Estimates of quantitative genetic variance components directly inform questions about the genetic basis of ID and should ultimately allow tests of alternative theories of mating system evolution.     

武夷山不同海拔植被土壤微生物量N时空变异

为了阐明我国中亚热带森林区土壤微生物量N的时空变异特征及其主要影响因子,在福建省武夷山国家自然保护区选择了常绿阔叶林(EBF,500 m)、针叶林(CF,1200m)、亚高山矮林(SDF,1800 m)和高山草甸(AM,2100 m)4种不同海拔植被类型土壤(0～10、10～25、25～40 cm)进行研究.结果表明,土壤微生物量N随着海拔高度的增加显著增加,在0～10 cm土层中EBF、CF、SDF、AM土壤微生物量N分别为106.7、140.8、254.9和355.8 mg·kg-1,不同海拔之间土壤微生物量N差异显著(P<0.05).土壤微生物量N在0～10 cm土壤表层最高,随着土壤深度的增加而逐渐减小.4种不同植被类型的3个土壤层次中土壤微生物量N均具有明显的季节动态变化,且变化规律一致,均表现为冬季最高,秋季次之,夏季最低.相关分析表明,在0～10 am土层影响土壤微生物量N沿海拔梯度空间变异的主要因子是土壤湿度、土壤有机质及全N含量,而影响土壤微生物量N季节性变异的主要因子是土壤水分与土壤温度.     

土壤因子对野生植物AM真菌的影响

1　引　　言关于生态因子对ＡＭ真菌发生和分布的影响 ,国内外均有报道[1,2 ,7] ,张美庆等[6] 比较系统地研究了我国东、南沿海七省ＡＭ真菌的生态分布 ;吴铁航[5] 报道了几种土壤因子对栽培作物根围内ＡＭ真菌分布的影响 .本文主要介绍土壤类型、质地、营养状况、ｐＨ等对野生植物根围ＡＭ真菌的侵染、孢子密度和种属分布的影响 .2　研究地区与研究方法2 1　研究地区概况山东省位于 33°2 5′～ 38°2 3′Ｎ ,114°36′～ 12 2°4 3′Ｅ之间 ,属暖温带大陆性季风气候 ,年平均气温 11～ 14℃ ,年平均降水量为 5 5 0～ 95 0ｍｍ .根据地貌不…     

环境因子对西藏高原草地植物丛枝菌根真菌的影响

对西藏高原不同草地类型建群种植物的研究结果表明,寄主植物根围土壤AM真菌孢子密度与菌根侵染率之间无相关性;不同海拔条件下温度、降水量等的显著变化对草地植物AM真菌的发育和侵染具有重要影响,不同草地类型、土壤质地对AM真菌的影响亦较明显;在一定范围内,孢子密度随土壤pH、有机质含量的提高分别呈显著增加(r=0.5319^*,n=20)和下降趋势(r=-0.1973,n=20),菌根侵染率与土壤pH、有机质含量间则分别呈一定程度的负相关和正相关;高磷土壤环境对AM真菌的产孢和侵染均具有不同程度的抑制作用;最适AM真菌发育和产孢的土壤pH、有机质和有效磷含量范围分别为8.0～8.7、3.8～4.8g·kg和7.8～10.1mg·kg^-1;中度特别是重度退化草地对AM真菌的繁殖和侵染均具有不利影响,适度放牧对AM真菌关键种的保持具有重要意义;AM真菌对沙生苔草、矮生嵩草和扁穗莎草根系均具有良好的侵染效应.     

Evolution of Inbreeding and Outcrossing in Ferns and Fern-Allies

Abstract Mating systems of 18 species of homosporous ferns follow a bimodal distribution, similar to that observed for seed plants (Schemske and Lande, 1985). Most species are highly outcrossing, a few are inbreeding, and two species examined to date have mixed mating systems. Equisetum arvense and several species of lycopods are also highly outcrossing. Several mechanisms, including inbreeding depression, antheridiogen, and ontogenetic sequences that result in effectively unisexual gametophytes, promote outcrossing in homosporous ferns and perhaps other homosporous pteridophytes as well. In some species of homosporous ferns, selection has favored the evolution of inbreeding as an adaptation for colonization. High levels of intra- and interpopulational gene flow via spore dispersal, coupled with high levels of intergametophytic crossing, generally lead to genetically homogeneous populations and species of homosporous ferns. However, rock-dwelling ferns and ferns from xeric habitats may exhibit significant population genetic structure due to physically patchy habitats. Reticulate evolution in homosporous ferns may be enhanced by high levels of intergametophytic crossing.     

Inbreeding depression in two species of Mimulus (Scrophulariaceae) with contrasting mating systems

We examined the effect of self- and cross-pollination on germination success, flowering probability, pollen and ovule production, survivorship, and adult aboveground biomass in two species of Mimulus with contrasting mating systems: the highly seifing M. micranthus and an outcrossing population of M. guttatus. Cross-pollinations were performed both within and between populations in order to examine the scale at which the genetic load is distributed. We found significant inbreeding depression in M. guttatus in four of the six traits, with the highest inbreeding depression observed in biomass (68% and 69% based on within- and between-population crosses, respectively) and lowest in ovule production (21% based on between-population crosses only). M. micranthus displayed significant inbreeding depression in only two of the six traits examined. Again, we observed the highest inbreeding depression in biomass (47–60% based on within- and between-population crosses, respectively), but both traits showing significant differences between self and outcross progeny expressed lower inbreeding depression than in M. guttatus. We detected no significant inbreeding depression for either pollen or ovule production in M. micranthus. An estimate of total inbreeding depression based on the multiplicative effects of all traits was also lower in M. micanthus than∗∗∗ in M. guttatus. Our results are consistent with the expected purging of genetic load in populations with high selfing rates. The absence of inbreeding depression in M. micranthus pollen and ovule production, two traits with strong links to fitness in a selfing annual, further suggests the important role of directional selection in determining the population's genetic load. Comparison of cross-pollinations made within and between populations revealed little evidence of divergence of genetic load among the M. micranthus and M. guttatus populations examined.     

三七丛枝菌根（AM）的研究

研究发现,丛枝菌根真菌(AMF)能侵染三七根系并形成典型的丛枝菌根(AM),侵染率在12%～30%,但侵染强度较弱。从三七根际采集的10个土样中共分离出15种AMF,Glomus属11种,Acaulospora属4种,分别是瘤状无梗囊霉、刺无梗囊霉、孔窝无梗囊霉、细齿无梗囊霉、地球囊霉、明球囊霉、缩球囊霉、单孢球囊霉、近明球囊霉、地表球囊霉、小果球囊霉、摩西球囊霉、何氏球囊霉、晕环球囊霉和网状球囊霉。其中,地球囊霉是三七的优势种。因此,AMF是三七丰产栽培中的一种潜在应用价值的生物资源。     

Infectivity and effectiveness of Glomus intraradices on micropropagated plants

Colonization by Glomus intraradices takes place very early within the root system of micropropagated plantlets of strawberry (var. avanta, elsanta), raspberry (var. himboqueen, Zeva I), and hortensia (var. leuchtfeuer). The arbuscular mycorrhizal fungus (AMF) did not colonize roots of the different hosts to the same extent, and considerable differences were observed between the varieties. The results reported here confirm that endomycorrhizal root colonization is affected by the host-fungus combination. The effects ranged from mutualistic (hortensia), through neutral (strawberry var. avanta, raspberry var. Zeva I) to negative (raspberry var. himboqueen and strawberry var. elsanta). Non-mycorrhized (control) plants of strawberry produced more runners than mycorrhized plants under controlled growth conditions (phytotron). Transfer of the potted plants to the field resulted in drastic alterations in overall growth and development within 4 weeks. Mycorrhized plants became healthy, and mycorrhized strawberry plants produced many stout runners. The number of the runners and their biomass were almost the same (var. avanta) and treated plants produced even more runners than the controls (var. elsanta). The authors have demonstrated the need to determine the specific effects of each species of AMF on individual prospective host plants prior to their utilization in the micropagation of plantlets.     

Production of Strigolactones by Arabidopsis thaliana responsible for Orobanche aegyptiaca seed germination

The germination stimulants produced by Arabidopsis thaliana, a host of root parasitic plants Orobanche spp. but not of arbuscular mycorrhizal (AM) fungi were examined. Root exudates from the hydroponically grown A. thaliana plants were subjected to reverse phase high performance liquid chromatography (HPLC) and retention times of germination stimulants inducing O. aegyptiaca seed germination were compared with those of strigolactone standards. In addition, the root exudates were analyzed by using HPLC linked with tandem mass spectrometry (LC/MS/MS). A. thaliana was found to exude at least three different germination stimulants of which one was identified as orobanchol. This is the first report of strigolactone production by a non-mycotrophic plant. These results together with recent knowledge imply that strigolactones have other unrevealed functions in plant growth and development.     

Maintenance of androdioecy in the freshwater shrimp, Eulimnadia texana: do hermaphrodites need males for complete fertilization?

Androdioecy (populations comprised of mixtures of males and hermaphrodites) is a rare mating system, found only in a few plants and animals. The rarity of this system stems from the limited benefits to males in an otherwise all-hermaphroditic population. One of the potential benefits to males is typified by the nematode Caenorhabditis elegans, in which hermaphrodites do not produce sufficient sperm to fertilize all of their eggs. Here we explore the possibility that males are needed for complete fertilization of hermaphrodites' eggs in a second androdioecious animal, the clam shrimp Eulimnadia texana. We compare the fertilization rate of outcrossed to selfed eggs to test whether the latter exhibit lower fertilization due to sperm limitation (as in C. elegans). Because this comparison confounds differences in egg fertilization due to sperm limitation with the potential for early inbreeding depression, we also used a third mating treatment, a brother/sister cross, to allow separation of sperm limitation from inbreeding depression. In both populations examined, the proportion of eggs that were fertilized decreased linearly with increasing relatedness: comparing eggs produced by outcrossing, brother/sister, and selfed matings, respectively. This pattern suggests that differences in fertilization among these three treatments were caused solely by inbreeding depression, and therefore that hermaphrodites are not sperm limited. These results are combined with previous data on this species to test whether the maintenance of males can be explained using a population genetics model specifically designed for this species.     

寄主植物和接种物对丛枝菌根菌接种势的影响(英文)

在盆栽条件下研究了丛枝菌根菌(arbuscular mycorrhizal fungi,AMF)单孢、多孢和菌根根段接种物及其寄主植物烟草(Nicotiana tabacum L.)、苏丹草(Sorghum sudanense(Piper)Stapf)和三叶草(Trifoliumrepens L.)对AMF Glomus macrocarpum Tul ＆ Tul、Glomus mosseae(Nicol ＆ Gerd.)Gerdemann ＆ Trappe、Glomusversiforme(Karsten)Berch和Sclerocystis sinuosa Gerdemann ＆ Bakhi发育和接种势值(value of inoculum poten-tial,VIP)的影响。用50个孢子或0.5g菌根根段接种物处理的感染迟缓期为28d,大大短于单孢接种处理(64d);前者的VIP和根系感染百分率(percentage of root colonization,PRC)均高于后者。50个孢子和0.5g菌根根段接种物两处理之间仅在感染的早期阶段存在差异。0.5g菌根根段接种物(烟草上G.versiforme菌除外)接种处理的VIP大于其他两种接种物的处理;而50个孢子或0.5g菌根根段接种物处理的PRC直至接种后70d仍高于单孢接种处理。三叶草上AMF的VIP显著大于其他两种寄主植物上的VIP。G.mosseae、G.versiforme和S.sinuosa的VIP则大于G.macrocarpum的处理。这表明不同AMF菌种能产生不同接种势值的接种物。烟草则是用于单孢接种和接种物生产的良好寄主植物。     

AM真菌和镰刀菌对西瓜根系几种酶活性的影响*

在温室盆栽条件下研究了丛枝菌根(Arbuscular Mycorrhiza, AM)真菌Glomus versiforme和西瓜枯萎镰刀菌Fusarium oxysporum f.sp. niveum对西瓜根系中过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)、β-1,3-葡聚糖酶和几丁质酶活性的影响。结果表明,接种AM真菌的西瓜根系中4种酶的活性均高于对照,先接种G. versiforme,后接种F. oxysporum f.sp. niveum处理的4种酶的活性均高于只接种F. oxysporum f.sp. niveum 的处理,且酶的活性峰值出现较早。表明接种G. versiforme 能预先诱导这4种酶的产生,提高其活性,从而提高西瓜对F. oxysporum f.sp. niveum侵染的抗性。接种G. versiforme的感枯萎病西瓜品种“郑杂5号”酶的增加幅度大于抗病品种“京欣1号”的接种处理,说明G. versiforme对提高感病西瓜品种酶活性的作用更大。     

Stimulation of Plant Growth and Drought Tolerance by Native Microorganisms (AM Fungi and Bacteria) from Dry Environments: Mechanisms Related to Bacterial Effectiveness

In this study we tested whether rhizosphere microorganisms can increase drought tolerance to plants growing under water-limitation conditions. Three indigenous bacterial strains isolated from droughted soil and identified as Pseudomonas putida, Pseudomonas sp., and Bacillus megaterium were able to stimulate plant growth under dry conditions. When the bacteria were grown in axenic culture at increasing osmotic stress caused by polyethylene glycol (PEG) levels (from 0 to 60%) they showed osmotic tolerance and only Pseudomonas sp. decreased indol acetic acid (IAA) production concomitantly with an increase of osmotic stress (PEG) in the medium. P. putida and B. megaterium exhibited the highest osmotic tolerance and both strains also showed increased proline content, involved in osmotic cellular adaptation, as much as increased osmotic stress caused by NaCl supply. These bacteria seem to have developed mechanisms to cope with drought stress. The increase in IAA production by P. putida and B. megaterium at a PEG concentration of 60% is an indication of bacterial resistance to drought. Their inoculation increased shoot and root biomass and water content under drought conditions. Bacterial IAA production under stressed conditions may explain their effectiveness in promoting plant growth and shoot water content increasing plant drought tolerance. B. megaterium was the most efficient bacteria under drought (in successive harvests) either applied alone or associated with the autochthonous arbuscular mycorrhizal fungi Glomus coronatum, Glomus constrictum or Glomus claroideum. B. megaterium colonized the rhizosphere and endorhizosphere zone. We can say, therefore, that microbial activities of adapted strains represent a positive effect on plant development under drought conditions.