寒温带地区典型森林类型中外生菌根真菌多样性和群落组成及其影响因素

外生菌根(ECM)真菌可促进宿主植物对土壤中水分和营养的吸收,提高宿主植物的抗逆性及对环境的适应,在森林生态系统的物质循环中发挥了重要作用。为探明寒温带地区ECM真菌多样性和群落组成以及土壤理化因子对真菌群落组成的可能影响机制,采用高通量测序(Illumina Miseq)平台对大兴安岭4种典型森林类型白桦、樟子松、兴安落叶松和偃松的根围土壤ECM真菌群落组成进行了分析。结果表明,4种典型森林类型根围土壤中共获得167个ECM真菌可操作分类单元(OTUs),隶属于2个门、4个纲、10个目、24个科、36个属。在门水平上,担子菌门(Basidiomycota)真菌的相对丰度占96.4%,子囊菌门(Ascomycota)真菌占3.6%。在属水平上,红菇属(Russula,30.2%)、丝膜菌属(Cortinarius,17.1%)、Piloderma(9.6%)、棉革菌属(Tomentella,7.2%)、丝盖伞属(Inocybe,7.2%)和蜡壳耳属(Sebacina,6.2%)的相对丰度均>5.0%,是该地区的优势ECM真菌类群。不同森林类型的优势ECM真菌在属水平上的组成存在显...     

Change in medium components and colony morphology due to mycelial growth of ectomycorrhizal fungusTricholoma bakamatsutake

Mycelia ofTricholoma bakamatsutake isolate No. 4 grew at temperatures ranging from 10 to 30°C, and the optimum was around 25°C. In well-buffered media of initial pH 5.0 and 6.0, No. 4 mycelia secreted gluconic acid and lowered medium pH. Mycelial growth then accelerated slightly; and with the exhaustion of glucose, growth and secretion of gluconic acid stopped. In 10 different media of initial pH 4.0–7.0, No. 4 mycelia showed higher gluconic acid secretion with higher initial pH. No. 4 mycelial grew best in pH 5.0 media, in which gluconic acid secretion was low. Mycelia of 29 isolates including No. 4 grew better in the media in which less glucose, total carbon and total nitrogen remained, and almost all isolates secreted gluconic acid. Most of the 29 isolates showed irregular colony shapes with rough mycelial fronts, brown pigmentation and aerial hypha on colony surfaces, and brown pigmentation of media under colonies. Dissimilarities were calculated with coded morphological characters on colonies, and similarity between isolates was found not to correlate with proximity of origin. Chlamydospores were observed on every colony of the 29 isolates. Chlamydospores were present on colonies of No. 4, reaching to 2 mm from the mycelial front, where brown pigmentation had not yet developed, and the numbers of chlamydospores incresed with mycelial aging.     

Determination and distribution of a female-specific protein in the brown planthopper, Nilaparvata lugens Stal (Homoptera: Delphacidae)

Electrophoretic analyses of hemolymph and body or ovary homogenates from reproducing females, males, and 5th instar nymphs of the brown planthopper, Nilaparvata lugens Stal, revealed a protein band of 175 kDa in females. An immunoblot test using antibody against this protein showed a positive reaction with a 175 kDa protein from female body or ovary homogenates. It is likely that this protein in hemolymph is vitellogenin (Vg). Distribution of Vg was determined by immunofluorescence and immunogold labeling techniques. The results showed that the positive immunofluorescence reactions were present in yolk particles, the intercellular space of follicle cells, hemolymph, and the epithelial plug of ovarioles. In addition, the yeast-like symbiotes (YLS) in mycetocytes of adults and various nymphal instars as well as those free in hemolymph or entering oocytes also exhibited a positive reaction. Electron micrographs showed that immunogold particles were found most in yolk mass and YLS over other tissues. Especially the YLS in various developmental stages all contained immunogold particles, implying that the symbiote is somewhat related with production of the female-specific protein.     

The evolutionary ecology of myco-heterotrophy

Nonphotosynthetic mycorrhizal plants have long attracted the curiosity of botanists and mycologists, and they have been a target for unabated controversy and speculation. In fact, these puzzling plants dominated the very beginnings of the field of mycorrhizal biology. However, only recently has the mycorrhizal biology of this diverse group of plants begun to be systematically unravelled, largely following a landmark Tansley review a decade ago and crucial developments in the field of molecular ecology. Here I explore our knowledge of these evolutionarily and ecologically diverse plant-fungal symbioses, highlighting areas where there has been significant progress. The focus is on what is arguably the best understood example, the monotropoid mycorrhizal symbiosis, and the overarching goal is to lay out the questions that remain to be answered about the biology of myco-heterotrophy and epiparasitism.     

Effects of monovalent cations on phosphate accumulation and storage of the ectomycorrhizal fungus Suillus bovinus

Comparative in vivo ³¹P-NMR studies of the fungus Suillus bovinus (L.: Fr.) O. Kuntze in pure culture have produced interesting new data. To investigate the response of phosphate metabolism to a change in external monovalent cations, samples were exposed to a Hoagland solution containing different monovalent cations Li⁺, Na⁺, K⁺, or Rb⁺ at 10 mM concentration. A method of nutrient cycling during analysis where the cation was changed and the phosphate kept constant allowed us to determine the kinetics of phosphate accumulation, storage and incorporation into polyphosphate following exposure to the range of test cations. Different external monovalent cations had different effects upon changes in the content of both phosphate and polyphosphate. Treatment with Li⁺, Na⁺, or Rb⁺ resulted in a change in phosphate accumulation to 60, 73, and 107% and in content of the intracellular mobile polyphosphate (polyP) to 119, 112, and 94%, respectively, compared with the control taken as 100%. The effect of each cation is related to its position in the periodic table. Reversing this process, i.e., exchanging with K⁺, returned phosphate metabolism to normal. Although, the increase in depolarization of the cell membrane should affect the internal pH, fungal metabolism using energy requiring mechanisms appeared necessary to maintain the intracellular pH. Thus, increasing contents of mobile polyP were the consequence of an increasing energy demand. On the other hand, the increasing depolarization of the cell membrane following the sequence Rb⁺ < K⁺ < Na⁺ < Li⁺ inhibited the net P_i accumulation. Furthermore, it is postulated that the P_i accumulation was also regulated by the intracellular content in polyP.     

外生菌根真菌对科尔沁沙地樟子松人工林衰退的影响

通过对科尔沁沙地东南缘樟子松人工林气温、地温及樟子松人工林根系分布的观测,从温度对外生菌根菌存活与生长影响的角度分析了沙地樟子松人工林衰退的现象,结果表明：由于沙地表层土壤（0～5cm）高温环境,外生菌根菌无法存活;在沙地20～40cm土层内,温度条件有利于外生菌根菌的存活、生长,而13～42年生沙地樟子松人工林树木平均78％的根系分布于该层,说明外生菌根菌的存在阻止或延缓了樟子松人工林的生长衰退,不是导致沙地樟子松人工林枯叶、枯梢、枯枝、死亡的原因．表层土壤外生菌根菌的缺乏使萌发的幼苗不能形成有效根系是导致沙地樟子松人工林不能天然更新的主要原因之一．     

外生菌根真菌对重金属铜镉污染土壤中油松生长和元素积累分布的影响

该实验选取处于生长期的油松(Pinus tabulaeformis)幼苗,研究土壤Cu、Cd胁迫条件下,美味牛肝菌(Boletus edulis)单独接种、红绒盖牛肝菌(Xerocomus chrysenteron)与美味牛肝菌混合接种处理,对油松幼苗的生长和重金属积累分布状况的影响,探讨不同接种对油松抗性的影响。研究发现,菌根接种不仅促进寄主油松的生长发育和生物量积累,而且显著降低油松体内的重金属积累浓度,减少重金属由根部向植物茎叶部分的转运。与单一接种相比,混合接种可以更加有效地缓解重金属对寄主的生物毒性,减少土壤中重金属元素向油松体内的转运。这种优势在高浓度的重金属胁迫环境下尤为明显。该实验中,在3 mg·kg^-1 Cd胁迫下,混合菌根油松的茎叶和根部Cd浓度仅为未接种对照的59.1%和70.7%,比单一菌根降低了11.3%和18.1%,而混合菌根植物的茎叶和根部生物量干重则分别为未接种对照的1.14和1.20倍,单一菌根为未接种对照的1.18和1.17倍。在400 mg·kg^-1Cu胁迫下,混合菌根植物茎叶和根部的干重分别是未接种植株的1.01和1.09倍,而混合菌根植物茎叶和根部的Cu浓度仅为未接种植株的61.8%和79.6%,比Boletus edulis菌根植物的Cu积累浓度下降了0.7%和3.8%。