Inoculation of micropropagated plantlets of Eucalyptus tereticornis with ectomycorrhizal fungi

Micropropagated plantlets of Eucalyptus tereticornis at the root initiation stage were inoculated in vitro with Amanita murina, Hysterangium incarceratum, Laccaria laccata, Pisolithus tinctorius (3 isolates), Scleroderma cepa and S. flavidum in order to select the most compatible ectomycorrhizal partner. H. incarceratum and the two Scleroderma species did not form mycorrhizas with E. tereticornis. Two local isolates of P. tinctorius formed significantly more mycorrhizas than the other isolates tested. Plantlets with mycorrhizas formed by one of the local isolates of P. tinctorius were transplanted to the nursery where their growth significantly exceeded that of non-mycorrhizal plants.     

Field survival of containerized red and jack pine seedlings inoculated with mycelial slurries of ectomycorrhizal fungi

Red pine and jack pine seedlings growing in styroblocks were inoculated 8 wk after sowing with mycelium/agar slurries of 3 mycorrhizal fungi (Laccaria bicolor, Scleroderma citrinum, and an unidentified basidiomycete), and one suspected mycorrhizal fungus (Cantharellula umbonata). Seedlings inoculated with L. bicolor developed mycorrhizae earlier and in greater numbers than the other inoculation treatments, with red pine out-performing jack pine in both respects. At 34 wk following sowing, seedlings were outplanted on a cleared xeric site in Baraga Co., in Michigan's Upper Peninsula. Seedlings inoculated with C. umbonata failed to form mycorrhizae and were not outplanted. Inoculation treatments did not affect shoot or root weight at outplanting. Red pine inoculated with L. bicolor averaged 21% and 19% greater survival compared with control seedlings after one and two years in the field, respectively. Other inoculation treatments failed to increase seedling survival for either tree species. Jack pine demonstrated higher overall survival than did red pine for both years in all corresponding inoculation treatments.     

Allocation of 14C-carbon in two species of larch seedlings infected with ectomycorrhizal fungi

The flow of labeled carbon in ectomycorrhizal and non-ectomycorrhizal seedlings of Japanese larch (Larix kaempferi Sarg.) and its F1 hybrid (Larix gmelinii Rupr. x L. kaempferi) was studied. Larch seedlings were grown in a greenhouse for 110 days with larch forest soil (FM) or Suillus grevillei (SM) inoculum, or in the absence of ectomycorrhizal fungi (NM). Shoots of colonized and NM seedlings were exposed to a pulse of 14CO2 for 1 h under natural light. Seedlings were harvested following 0, 6 and 24 h of exposure to 14CO2. At the final harvest, SM seedlings of Japanese larch and hybrid larch allocated 2.6 and 2.5% more 14C, respectively, to roots than NM seedlings. In contrast, FM seedlings of Japanese larch and hybrid larch allocated 6.5 and 18.0% more 14C, respectively, to the stem than NM seedlings. Of the total 14C detected in needle, stem and root fractions, FM and SM seedlings allocated a greater proportion than NM seedlings, perhaps because FM and SM seedlings had significantly (P < 0.05) higher photosynthetic rates than NM seedlings. As a result, FM and SM seedlings had greater dry masses than NM seedlings. Concentrations of nitrogen and phosphorus in FM and SM seedlings were significantly (P < 0.05) higher than in NM seedlings, as was stomatal conductance.     

浅谈城市街道绿化苗木成活率的提高

城市街道绿地的自然环境条件要比庭院、居住区绿地的环境条件差得多。除了土壤板结、路面辐射温度高、空气干燥、烟尘和有害气体危害大外，还受地上、地下管线影响。容易造成人为和机械损伤，而且所植树木多为大中型乔灌木。所以城市街道绿化苗木的栽植要比一般园林绿化的技术要求更高、难度更大。城市绿化建设过程中，设计、施工单位要根据施工场地的自然地质、气候、土壤条件、各种乔灌木及花草的生物学特性和生态学特性，适地适树地进行树种、苗木配置，编制符合实际情况的绿化种植设计方案。     

两株外生菌根真菌对盐渍土壤中黑松幼苗生长的影响

为了研究外生菌根真菌对宿主植物黑松幼苗耐盐性的影响,采用盆栽实验,将成功侵染菌种土生空团菌(Cg)、紫晶蜡蘑(La)的黑松幼苗移栽于盐渍土壤中,培育3个月后,测定相关生理指标。结果表明:1)与非菌根化幼苗相比,接种菌根真菌Cg和La显著提高了针叶叶绿素a(由0.78 mg/g FW增加到1.27 mg/g FW和1.47 mg/g FW)和叶绿素b(由0.28 mg/g FW增加到0.40 mg/g FW和0.43 mg/g FW)的含量,增加了宿主体内脯氨酸含量(地上部:La> Cg> NM;地下部:La> Cg> NM),增强了K^+的吸收、转运,有效地维持(Cg菌种)或是降低(La菌种)了宿主地上部分Na^+/K^+的比值;显著(P <0.05)降低了宿主幼苗地下部的Na^+/K^+比值(由0.70降低到0.47和0.64)。2)外生菌根真菌有利于松树幼苗的生长,提高了其耐盐性,但因菌种而异(La> Cg)。深入研究不同菌种对不同宿主植物耐盐性的影响,将会成为后续菌根技术研究的一个重要方向,为沿海滩涂盐碱地的植被恢复提供理论依据及技术支持。     

Soil DIC uptake and fixation in Pinus taeda seedlings and its C contribution to plant tissues and ectomycorrhizal fungi

Plants can acquire carbon from sources other than atmospheric carbon dioxide (CO(2)), including soil-dissolved inorganic carbon (DIC). Although the net flux of CO(2) is out of the root, soil DIC can be taken up by the root, transported within the plant, and fixed either photosynthetically or anaplerotically by plant tissues. We tested the ability of Pinus taeda L. seedlings exposed to (13)C-labeled soil DIC and two NH(4)(+) availability regimes to take up and fix soil DIC. We also measured the concentration and distribution of the fixed soil DIC within the plant and mycorrhizal tissues, and quantified the contribution of soil DIC to whole-plant carbon (C) gain. Seedlings exposed to labeled DIC were significantly enriched in (13)C compared with seedlings exposed to unlabeled DIC (6.7 versus -31.7 per thousand). Fixed soil DIC was almost evenly distributed between above- and belowground biomass (55 and 45%, respectively), but was unevenly distributed among tissues. Aboveground, stem tissue contained 65% of the fixed soil DIC but represented only 27% of the aboveground biomass, suggesting either corticular photosynthesis or preferential stem allocation. Belowground, soil DIC had the greatest effect (measured as (13)C enrichment) on the C pool of rapidly growing nonmycorrhizal roots. Soil DIC contributed approximately 0.8% to whole-plant C gain, and approximately 1.6% to belowground C gain. We observed a slight but nonsignificant increase in both relative C gain and the contribution of soil DIC to C gain in NH(4)(+)-fertilized seedlings. Increased NH(4)(+) availability significantly altered the distribution of fixed soil DIC among tissue types and increased the amount of fixed soil DIC in ectomycorrhizal roots by 130% compared with unfertilized seedlings. Increased NH(4)(+) availability did not increase fixation of soil DIC in nonmycorrhizal roots, suggesting that NH(4)(+) assimilation may be concentrated in ectomycorrhizal fungal tissues, reflecting greater anaplerotic demands. Soil DIC is likely to contribute only a small amount of C to forest trees, but it may be important in C fixation processes of specific tissues, such as newly formed stems and fine roots, and ectomycorrhizal roots assimilating NH(4)(+).     

Response of tree seedlings to aluminum

This review focuses on the mechanisms underlying aluminum (Al) toxicity in trees. The major topics discussed include the uptake and localization of Al, effects of Al on growth and composition, factors determining the response to Al, proposed mechanisms of Al resistance, and the occurrence of Al phytotoxicity under field conditions.     

General principles in the community ecology of ectomycorrhizal fungi

Introduction

Knowledge of the factors that determine ectomycorrhizal fungal community structure is essential in many areas of practical significance including conservation, habitat restoration, prevention or amelioration of species invasions, and the prediction of responses to climate change. With respect to these goals, however, community ecology, in general, and ectomycorrhizal fungal community ecology, in particular, have been rather disappointing.

Discussion

Indeed, some feel that community ecology is, at best, an esoteric discipline and, at worst, an inane one. But there is hope. As we apply what has been learned about other organisms concerning the relationships between functional traits and success (abundance), it may be possible to elucidate general principles that govern much of the structuring of ectomycorrhizal fungal communities.

Conclusion

A hierarchical model of ectomycorrhizal fungal community structure is presented that involves abiotic filtering of immigrant propagules based on functional traits, followed by interspecific competition as ameliorated by disturbance and habitat partitioning, the outcomes of which are dependent on functional traits.     

Effect of ammonium on glutamine synthetase activity in ectomycorrhizal fungi, and in mycorrhizal and non-mycorrhizal Scots pine seedlings

The influence of ammonium on glutamine synthetase activity (GS, EC 6.3.1.2) was studied in three species of ectomycorrhizal fungi, Paxillus involutus (Batsch:Fr) Fr, Piloderma croceum Erikss. and Hjortst. and Suillus variegatus (Fr) O Kuntze growing in pure culture, as well as in the roots and needles of nursery-grown, non-mycorrhizal and mycorrhizal Scots pine (Pinus sylvestris L.) seedlings inoculated with Paxillus involutus or Piloderma croceum as the symbiont. In response to increasing concentrations of ammonium in the nutrient solution, GS activity (expressed on a dry weight basis) increased slightly in Suillus variegatus but not in the other fungi. Glutamine synthetase activity increased in the roots and decreased in the needles of non-mycorrhizal seedlings as the ammonium concentration in the nutrient solution was increased from 0 to 1 mM, but no response was noted with further increases from 1 to 12 mM. Interspecies differences in GS activity were noted among the fungi growing in pure culture, but no significant interspecies differences were observed among the same fungi in the mycorrhizal state.     

Inoculation of Acacia holosericea with ectomycorrhizal fungi in a semiarid site in Senegal: growth response and influences on the mycorrhizal soil infectivity after 2 years plantation

The main objectives of this study were to determine the influence of several strains of ectomycorrhizal fungi on the growth of Acacia holosericea in a dry tropical environment and their short-term effect on indicators of ecosystem soil conditions such as biological soil properties (microbial biomass, mycorrhizal soil infectivity). Three fungal strains have been tested: Pisolithus albus IR100, P. albus COI024 and Scleroderma dictyosporum IR109. Ectomycorrhizal inoculation has significantly enhanced the growth (shoot and root biomass) of A. holosericea seedlings after 4 months culture in glasshouse conditions in a disinfected soil. In field conditions, the transplanting shock was less important for the ectomycorrhized trees. After 2 years, the inoculated trees had a better growth than that recorded in the control treatment. Ectomycorrhizal inoculation has significantly stimulated height, leave and wood biomass, root biomass of A. holosericea trees. Moreover, this fungal inoculation has significantly modified the leaf nutrient contents for P, N and phenols. Microbial biomass and mycorrhizal soil infectivity were also larger in the inoculated plots.Ectomycorrhizal inoculation could be of great relevance to improve the reafforestation process of degraded areas with legumes fast growing trees. This biological practice could also ameliorate soil characteristics such as microbial biomass or mycorrhizal soil infectivity.     

Inoculation of Picea abies (L.) Karst. seedlings with vegetative inocula of ectomycorrhizal fungi Suillus bovinus (L.: Fr.) O. Kuntze and Inocybe lacera (Fr.) Kumm.

Perlite-peat substrate (2:1 v:v) fumigated with Basamide was inoculated with vegetative inocula (a mixture of perlite and peat moistened with the MMN liquid medium) of ectomycorrhizal fungi Suillus bovinus (isolate TUZ 105) and Inocybe lacera (isolate X/14) immediately before seeding with Norway spruce (Picea abies [L.] Karst.) in a nursery bed. Suillus inoculum was applied at rates of 0.5; 1.0; 1.5 and 2.0 litres per m², Inocybe inoculum at rates of 0.5 and 1.5 litres per m². At the end of the first growing season, all inoculation treatments showed a significantly greater mycorrhizal infection of bareroot seedlings compared to that found in both fumigated and unfumigated controls. The ectomycorrhizal 1-year-old seedlings were transplanted into containers. At the end of the second year, ectomycorrhizal infection of the 2-year-old container-grown seedlings was considerably less than that of the 1-year-old barerooted seedlings, probably as a consequence of too high fertility and/or insufficient porosity/aeration of pure peat moss medium. There was no difference in seedling growth between inoculated and uninoculated seedlings throughout the experiment.     

Spores of ectomycorrhizal fungi as inoculants for Nothofagus pumilio and exotic conifer seedlings in Patagonia, Argentina: their activity and conservation

Ectomycorrhizal (EM) fungi incorporation in nursery production is necessary for afforestation with exotic tree species and native forests restoration programs. The fact that spore use as EM inocula is inexpensive and effective, makes it an option more realistic than vegetative inoculum production for many regions around the world. To determine spore activity from EM species selected as inoculants for Nothofagus pumilio and exotic conifers planted in Patagonia, two conservation methods were applied (i.e., dried fruit bodies and spore slurries), and their change over time was assessed (over 8–9 months). Spore activity decreased significantly with time for both native and exotic EM species. Conservation methods showed no significant differences for N. pumilio EM species considered together or for exotic conifer EM species. However, spore activity of different EM species behaved differently with conservation method and over time when considered separately. Taxa which better kept spore activity over time were Austropaxillus statuum and Setchelliogaster fragilis for N. pumilio, and Inocybe kauffmanii for exotic conifers. However, considering together fruit body spore density and spore activity, the species Hallingea purpurea and Cortinarius sp. also appeared as suitable for N. pumilio and Rhizopogon roseolus, R. villosulus, Suillus luteus and S. lakei for exotic conifers. Spore density found in EM fungal fructifications were also established in order to estimate fructification weights necessary to apply a reference dose of active spores in inoculation programs.     

The response of ectomycorrhizal fungi on Pinus densiflora seedling roots to liquid culture

Japanese red pine (Pinus densiflora) seedlings taken from a nursery were grown in liquid culture with all roots entirely submerged in water. The aims of the present study were to observe the reactions of preformed ectomycorrhizae to liquid culture and to examine new infections by ectomycorrhizal fungi on newly formed root tips in liquid culture. Inoculation levels were controlled by trimming the ectomycorrhizal roots to one of three selected root lengths. The results showed that the mantles of pre-formed ectomycorrhizae were lost during the 8 weeks of the liquid culture and that these preformed root tips became blackish and wrinkled, but Hartig nets remained in these blackish root tips. On the newly formed lateral root tips, no ectomycorrhizal mantles were formed, although Hartig nets were found. In addition, the level of inoculum did not affect the frequency of Hartig nets in newly formed root tips, suggesting that the density of inoculum was more important than the amount of inoculum for new infection. In conclusion, ectomycorrhizal fungi endured and infected new roots while submerged; however, only Hartig nets were formed and not mantles.     

Interactions between Tricholomopsis rutilans and ectomycorrhizal fungi in paired culture and in association with seedlings of lodgepole pine and Sitka‐spruce

Interactions between two isolates (Avondhu and CBS) of Tricholomopsis rutilans and ectomycorrhizal fungi (Hebeloma crustuliniforme, Laccaria laccata and Paxillus involutus) were examined on agar medium in the presence or absence of woodchips. The CBS isolate showed more competitiveness than the Avondhu isolate, when paired with ectomycorrhizal fungi. There was an inhibition of the growth of mycelium of the ectomycorrhizal fungi ranging from overgrowth to avoidance. The ectomycorrhizal fungi exhibited hyphal abnormalities such as discoloration, excessive vacuolation and curling. Formation of mycorrhizas by H. crustuliniforme in Pinus contorta and Picea abies was unaffected by the presence of the CBS isolate, whereas a reduction occurred in the presence of the Avondhu isolate. In non‐mycorrhizal seedlings of both conifers, the Avondhu isolate reduced root and shoot dry mass and number of root laterals and caused a lower number of short roots in lodgepole pine. The significance of these interactions between T. rutilans and ectomycorrhizal fungi in paired culture and during symbiosis is discussed.     

Frost heaving of forest tree seedlings: a review

Soil frost heaving is the result of the formation of ice lenses in the soil caused by a segregation of the soil water. Ice lenses are growing from below and pushed upward. Seedlings heave when they are pushed out of the ground by the ice sheet formed at the surface of the soil. Frost heaving may greatly reduce growth and survival of forest tree seedlings particularly in regions where freezing and thawing are accompanied by high soil moisture. Resistance to frost heaving increases with size of seedling as the ability of a seedling to anchor itself increases. A few methods, such as fertilizing, choice of planting spots, sowing or planting at the proper time, shading, and use of mulches, appear to be effective in controlling frost heaving. Shade from natural plant cover can greatly reduce frost heaving.     

培养基种类对外生菌根真菌生长的影响

外生菌根是真菌同寄主植物形成的一种互益的联合体 ,它对寄主植物的有益作用主要表现在 :扩大寄主植物根系的吸收面积 ,产生植物激素等生长调节物质以及抗生素和某些挥发性物质 ,进而增强了寄主植物的抗逆性 ,同时它对许多林木根部土传病害有良好的防治效果。目前 ,外生菌根主要应用在容器育苗、苗圃育苗和大规模造林等方面 ,在干旱地区、草原、侵蚀地、工业废地、荒地及采伐迹地造林上也都需要外生菌根。随着菌根研究的不断深入 ,人们发现在生长过程中 ,不同菌根真菌对营养的要求不同。因此 ,用不同的培养基 ,在 2 5℃无光条件下培养、筛选…     

The lateral spread of tree root systems in boreal forests: Estimates based on N uptake and distribution of sporocarps of ectomycorrhizal fungi

In nutrient poor environments, such as boreal forests, many of the most important interactions between plants take place belowground. Here, we report the results of two approaches to obtain estimates of the lateral spread of tree roots.     

Tolerance of broadleaved tree and shrub seedlings to preemergence herbicides

Isoenzymes were used to study the genetic variation of 121 mature trees of Sorbus torminalis in a natural stand and a subset of 21 high yielding seed trees in the same stand used for a commercial harvest. Eight enzyme systems were studied. The genetic variation of the mature stand was higher than that of other stands reported in the literature. However, this level of genetic variation was not represented to the same extent by the seeds of the commercial harvest. Differences between the bud sample taken from the mature stand and the seed sample taken from the commercial subset were particularly obvious with respect to diversity measures and heterozygosities. The hypothetical gametic multilocus diversity (HGMD) of a bud sample of the mature Sorbus torminalis trees was more than 70% higher (94.1) than the value of the seed harvest sample (55.1). Deviations between the genetic structures of both samples were statistically significant. There is no indication that inbreeding is an essential component of the mating system of Sorbus torminalis. The potential causes for the lack of Sorbus torminalis seedlings and saplings originated from seeds and their consequences for regenerating this species are discussed. This research underscores that sampling a forest tree population for commercial harvest can result in a statistically significant reduction in the genetic diversity of the sampled group relative to the overall population.     

Management of ectomycorrhizal symbionts associated to useful exotic tree species to improve reforestation performances in tropical Africa

? The objective of this review was to summarize scientific data on the symbiotic status of exotic tree species useful in tropical Africa, and to update reports about their growth improvement through microbial inoculations, especially ectomycorrhizal symbionts.

? The studies reviewed microbial symbionts associated to exotic tree species belonging to Myrtaceae, Pinaceae, Casuarinaceae and Leguminosae. In their native areas, these trees are associated either with ectomycorrhizal (ECM) fungi (e.g. Pinaceae) or both ECM and arbuscular mycorrhizal (AM) fungi (e.g. Eucalyptus), or sometimes as in Casuarina and Acacia with three coexisting symbionts (nitrogen fixing bacteria, ECM and AM fungi). In their new habitats, using highly efficient mycorrhizal fungi, controlled mycorrhization experiments have pointed out the importance of root symbionts in establishment and growth of exotic tree species such exotic pines or Australian acacias.

? Since the challenge in sylviculture and reforestation was to determine the best compromise between symbiotic compatibility and efficiency of both partners under local soil constraints, further researches have to be encouraged to elucidate the complexity of these tree symbioses in terms of diversity, interaction and effectiveness of their symbiotic partners for their better exploitation in reforestation programmes.

     

Nursery inoculation of Eucalyptus seedlings in Western Australia and Southern China using spores and mycelial inoculum of diverse ectomycorrhizal fungi from different climatic regions

A large-scale ectomycorrhizal (ECM) fungus inoculation program was conducted in plantation forest tree nurseries in Australia and China over a period of 2 years. These experiments used a wide diversity of fungi (90 isolates belonging to 23 genera), most of which were obtained from Australian eucalyptus plantations or forests. These trials compared the effectiveness of mycelial slurries (homogenised liquid fungal cultures) and spore suspensions (ground dried fruit bodies) as inoculum forms in nurseries with widely differing management regimes. The success rate of inoculation was moderate, regardless of nursery management regime (38% overall). However, there were substantial differences in overall performance between fungal genera, with agaricoid genera, such as Descolea and Laccaria, and hypogeous (truffle-like) fungi performing better than sequestrate genera, such as Pisolithus and Scleroderma. Comparison of congeneric fungal isolates from different climatic regions did not show significant differences in the performance of fungi from regions where climatic conditions were most similar to nursery conditions relative to those from disparate climatic regions (tropical, temperate, or mediterranean). There was a higher overall success rate for inoculation with spore suspensions (49%) than for mycelial slurries obtained from liquid cultures (35%). Spore-based inoculum was also easier to use and much less expensive to produce than mycelial slurries. It is recommended that future studies investigate the use of mixtures of fungi and attempt to optimise spore germination to increase the reliability of eucalypt seedling nursery inoculation.