Ectomycorrhizal fungal biomass in roots and uptake of P from apatite by Pinus sylvestris seedlings growing in forest soil with and without wood ash amendment

Forest soil from an experimental Norway spruce forest with four levels of wood ash addition (0, 1, 3 and 6 tonnes ha^–1) was used to inoculate pine (Pinus sylvestris) seedlings with indigenous ectomycorrhizal (EM) fungi. Uptake of ³²P and ⁸⁶Rb in a root bioassay was used to estimate the demand for P and K by seedlings grown in the different soils. Utilisation of P from apatite was tested in a laboratory system where uptake by the ectomycorrhizal mycelium was separated from uptake by roots. The demand for P and K in the seedlings was similar regardless of the ash treatment. Variation in EM levels, estimated as fungal biomass (ergosterol) in roots, was large in the different soils, but not related to ash addition. Uptake of P from apatite was, on average, 23% of total seedling P and was not related to EM levels. It was concluded that the improved P uptake from apatite by EM fungi found in earlier studies is probably not a general phenomenon among EM fungi. The small effect of ash addition on EM levels and P uptake suggests that addition of granulated wood ash is a forest management treatment that will have only minor influence on ectomycorrhizal symbiosis.     

Ectomycorrhizal colonization on black spruce and jack pine seedlings outplanted in reforestation sites

Six-week-old, mycorrhiza-free, bareroot jack pine and black spruce seedlings were outplanted in ten reforestation sites, situated between 45–48° latitude N and 69–74° longitude W, within the province of Quebec, representing diverse operational forestry disturbances and ecological conditions. Two months after outplanting, root systems of black spruce seedlings had fewer mycorrhizae than those of jack pine seedlings. Ectomycorrhizal colonization on black spruce seedlings did not vary significantly with the reforestation site. Percent mycorrhizal colonization for these seedlings was positively correlated with seedling dry weight while with the jack pine seedlings, mycorrhizal colonization varied significantly with the outplanting site and there was no correlation between mycorrhizal formation and seedling dry weight. Multiple linear regressions showed pH to be a determinant soil factor for mycorrhizal colonization for the two species. Drainage was the other influential factor affecting colonization of black spruce while organic matter accumulation was more important for jack pine. Inoculation with selected ectomycorrhizal fungi could be more important for black spruce than for jack pine seedlings.     

Habitat matters: The role of spore bank fungi in early seedling establishment of Florida slash pines

This study investigated broad patterns in communities of ectomycorrhizal fungi from three Florida habitats (sandhills, scrub, and pine rocklands) and the ability of spore bank fungi to associate with Pinus elliottii (slash pine) and Pinus densa (south Florida slash pine). Efforts to replant pines in the endangered pine rocklands are vital to the persistence of this habitat, yet little is known about the ectomycorrhizal fungi communities or how they may differ from those in other pine-dominated habitats in Florida. We used high-throughput amplicon sequencing (HTS) to assess baseline fungal communities and greenhouse bioassays to bait ectomycorrhizal fungi using seedlings. HTS soil data recovered 188 ectomycorrhizal species but only a few subsequently colonized the bioassay seedlings. We recovered 21 ectomycorrhizal species on pine seedlings including common spore bank fungi such as Cenococcum, Suillus, and Tuber, but Rhizopogon species were dominant across all sites and habitats. Habitat type and site were significant variables influencing the community composition of the total soil fungal community, soil ectomycorrhizal community, and the fungi found on seedling root tips. However, we found no significant differences between the ectomycorrhizal communities on seedling roots from the two Pinus species.     

Ectomycorrhizal responses to organic and inorganic nitrogen sources when associating with two host species

While it is established that increasing atmospheric inorganic nitrogen (N) deposition reduces ectomycorrhizal fungal biomass and shifts the relative abundances of fungal species, little is known about effects of organic N deposition. The effects of organic and inorganic N deposition on ectomycorrhizal fungi may differ because responses to inorganic N deposition may reflect C-limitation. To compare the effects of organic and inorganic N additions on ectomycorrhizal fungi, and to assess whether host species may influence the response of ectomycorrhizal fungi to N additions, we conducted an N addition experiment at a field site in the New Jersey pine barrens. Seedlings of two host species, Quercus velutina (black oak) and Pinus rigida (pitch pine), were planted at the base of randomly-selected mature pitch pine trees. Nitrogen was added as glutamic acid, ammonium, or nitrate at a rate equivalent to 227.5 kg ha⁻¹ y⁻¹ for eight weeks, to achieve a total application of 35 kg ha⁻¹ during the 10-week study period. Organic and inorganic N additions differed in their effects on total ectomycorrhizal root tip abundance across hosts, and these effects differed for individual morphotypes between oak and pine seedlings. Mycorrhizal root tip abundance across hosts was 90 % higher on seedlings receiving organic N compared to seedlings in the control treatment, while abundances were similar among seedlings receiving the inorganic N treatments and seedlings in the control. On oak, 33–83 % of the most-common morphotypes exhibited increased root tip abundances in response to the three forms of N, relative to the control. On pine, 33–66 % of the most-common morphotypes exhibited decreased root tip abundance in response to inorganic N, while responses to organic N were mixed. Plant chemistry and regression analyses suggested that, on oak seedlings, mycorrhizal colonization increased in response to N limitation. In contrast, pine root and shoot N and C contents did not vary in response to any form of N added, and mycorrhizal root tip abundance was not associated with seedling N or C status, indicating that pine received sufficient N. These results suggest that in situ organic and inorganic N additions differentially affect ectomycorrhizal root tip abundance and that ectomycorrhizal fungal responses to N addition may be mediated by host tree species.     

The extraction and quantification of ergosterol from ectomycorrhizal fungi and roots

Recently, ergosterol analysis has been used to quantify viable fungal biomass in resynthesized ectomycorrhizae. An objective of our study was to quantify ergosterol in a range of ectomycorrhizal isolates under differing growth conditions. In addition, we tested the applicability of the method on field-collected roots of ectomycorrhizal and vesicular-arbuscular (VA) mycorrhizal plants. Quantification of sitosterol as a biomass indicator of plant roots was also undertaken. Ergosterol was not detected in roots of uninoculated Betula populifolia seedlings, and sitosterol was not detected in an ectomycorrhizal fungal isolate but was present in birch roots. Ergosterol was produced in all isolates examined, which represented the major orders of ectomycorrhizal fungi. The range of values obtained, from 3 to nearly 18 g ergosterol mg^-1 dry mass, agrees well with reported values for other mycorrhizal and decomposer fungi. Hyphal ergosterol was the same during growth on phytic acid and KH₂PO₄. Reduction of growth temperature from 25° C to 15° C had little effect on ergosterol content of cultures harvested at similar growth stages. Ergosterol and sitosterol were detected in field-collected ectomycorrhizae of B. populifolia and Pinus sylvestris and VA mycorrhizae of Acer rubrum and Plantago major. Both ergosterol content and ergosterol to sitosterol ratios were significantly lower in VA mycorrhizae than ectomycorrhizae. Calculations of viable fungal biomass associated with field-collected roots were in agreement with those reported by others using the method on resynthesized ectomycorrhizae. Estimates of total mass could be obtained for field-collected B. populifolia roots by a simultaneously using ergosterol to estimate fungal biomass and sitosterol to estimate root mass. Some potential applications and limitations of sterol quantification in studies of mycorrhizal physiology and ecology are discussed.     

Root soluble carbohydrates of Afzelia africana Sm. seedlings and modifications of mycorrhiza establishment in response to the excision of cotyledons

Stem length, number of secondary lateral roots, shoot dry weight and reducing sugar concentrations of root were significantly reduced when translocation of reserves from cotyledons to the roots of Afzelia africana seedlings was interrupted by complete or partial cotyledon excision. The sucrose but not the glucose concentration of lateral roots also decreased significantly after complete cotyledon excision. Hartig net development rather than fungal sheath formation was affected after inoculation with the early fungal isolate E1 and by both late-stage fungal isolates L1 and L2 after partial or complete cotyledon excision. However, mycorrhizal colonization by the early fungal isolate E2 was not affected by cotyledonary reserves, suggesting that this fungal isolate has a lower carbohydrate requirement than fungal isolates E1, L1 and L2. The late-stage fungal isolates L1 and L2 induced a hypersensitivity reaction by epidermal cell walls of the host plant after complete cotyledon excision, suggesting they are more dependent than the early fungal isolate E1 on available root carbohydrate substrates for ectomycorrhizal colonization. These results are discussed in the light of the hypothesis that early and late-stage fungi were different carbohydrate requirements, and that the time sequence of colonization was related to the root carbohydrate status, which increased with time.     

Nitrogen amendments reduce the growth of extramatrical ectomycorrhizal mycelium

The effect of three different nitrogen sources on the growth of external ectomycorrhizal mycelium was studied in Perspex micorocosms. Nonsterile peat was used as substrate. Five different fungal isolates growing in symbiosis with pine seedlings were investigated: two isolates of Paxillus involutus, one of Suillus bovinus and two unidentified ectomycorrhizal fungi isolated from ectomycorrhizal root tips. Three different nitrogen sources were used: ammonium as (NH₄)₂SO₄, nitrate as NaNO₃ and a complete nutrient solution (Ingestad 1979), and three different nitrogen concentrations, 1, 2 or 4 mg N/g dry wt. of peat. The mycelial growth of all fungi was found to be negatively affected by the nitrogen amendments, although the sensitivity to nitrogen varied between the isolates. One of the unidentified isolates was extremely sensitive and growth was completely inhibited by all nitrogen treatments. In contrast, the growth of one of the P. involutus isolates was only slightly reduced by the nitrogen amendments. The different nitrogen sources all reduced growth, and since no significant difference was found between the nitrogen sources or between the different nitrogen concentrations the results were pooled to give one value that summarized the effect of nitrogen on mycelial growth. Thus, the mycelial growth of one of the two P. involutus isolates was reduced to approximately 80% of the growth in the control, the other P. involutus and one of the unidentified fungi, vgk 2 89.10, were reduced to 40–50% of the control growth, S. bovinus to 30% of the control and the most sensitive fungus, the unidentified isolate vg 1 87.10, was reduced to 3% of the growth in the control treatment. In all experiments, the shoot to root ratio generally increased, mainly as a result of increased shoot growth.     

An ericoid shrub plays a dual role in recruiting both pines and their fungal symbionts along primary succession gradients

Relative importance of positive and negative interactions between plant species may change along disturbance and resource gradients. Positive interactions are suggested to prevail in low resource, low productivity (high stress) conditions and negative interactions in high resource availability. A dwarf shrub, mountain crowberry Empetrum nigrum ssp. hermaphroditum, is known to have allelopathic impacts on both Scots pine Pinus sylvestris and its ectomycorrhizal symbionts. We aimed to study if the outcome of Empetrum impacts on Scots pine changes along primary succession gradients on the dune shores of Bothnian Bay, in Finland, where abiotic stress gradually changes to biotic stress along the succession. We found that Empetrum may act as a facilitator despite its allelopathic effects, since the proportion of Scots pine seedlings established in Empetrum patches was higher than in patches without the shrub in early and mid succession stages, whereas patches without Empetrum were preferred in late succession. The amount of mycelial fungal biomass (ergosterol) in the soil in the vicinity of the seedling roots was higher in Empetrum patches than in patches without Empetrum and it increased along the succession gradient. Proportion of pine root tips colonised by suilloid morphotypes with abundant external mycelia and the diversity of ectomycorrhizal morphotypes were higher in mid successional stage in Empetrum patches compared to patches without Empetrum. Our results suggest that in the harsh physical conditions of the dune shore Empetrum facilitates pine seedling establishment in the early and mid stages of succession by providing mechanical and physical shelter whereas in late succession negative interactions (competition and allelopathy) between the shrub and the pine are dominating. To our knowledge we present the first finding that an ericoid mycorrhizal shrub could enhance both the performance of the ectomycorrhizal host tree and the tree's fungal symbionts.     

Salinity effects on germination,growth, and seed production of the halophyte Cakile maritima

The growth ofEucalyptus regnans seedlings in forest soil is enhanced when it has been air-dried. In undried forest soil seedlings grow poorly and develop purple coloration in the foliage, indicating P deficiency. This paper reports the results of pot experiments designed to investigate the relationship between growth and P acquisition, ectomycorrhizal infection and age of seedlings grown in air-dried and undried soil. The effect on seedling growth of their inoculation with air-dried or undried soil or with ectomycorrhizal roots from plants growing in air-dried or undried soil was also investigated. Ectomycorrhizal root tips were detected in 3-week-oldE. regnans seedlings in both air-dried and undried soil, and from then on the frequency of ectomycorrhizal root tips increased rapidly. In air-dried soil, seedlings were fully ectomycorrhizal at 9 weeks, and the occurrence of maximum ectomycorrhizal infection coincided with enhanced P acquisition and the initiation of rapid seedling growth. In undried forest soil, seedling growth remained poor, even though the seedlings had well-developed ectomycorrhizae and the incidence of ectomycorrhizal root tips was the same as in air-dried soil. The dominant ectomycorrhizae in airdried soil were associated with an ascomycete fungus, whereas in undried, undisturbed soil they were commonly associated with basidiomycete fungi. Inoculation of sterile soil/sand mix with washed ectomycorrhizal roots from air-dried soil increased the P acquisition and growth of the seedlings significantly compared with controls, whereas ectomycorrhizal inocula from undried soil had no effect on seedling growth, although both inocula resulted in a similar incidence of ectomycorrhizal root tips. Similarly, addition of a small amount of air-dried soil into sterile soil/sand mix resulted in a significantly greater increase in the P content and dry weight of the seedlings, compared with the control, than addition of undried soil. In both treatments, the incidence of ectomycorrhial root tips was similar. As (i) the differentiation in seedling growth between air-dried and undried soil occurred after seedlings became ectomycorrhizal, (ii) the dominant ectomycorrhizae in air-dried soil were different from those in undried soil, and (iii) inocula from air-dried soil, but not from undried soil, stimulated seedling growth in sterile soil/sand mix, it is concluded that development of particular ectomycorrhizae may be involved in seedling growth stimulation and enhanced P acquisition associated with air drying of forest soil.     

An ectomycorrhizal fungus,Cenococcum geophilum,in a coastal pine forest has a high tolerance for an insecticide used to control pine wilt disease

Cenococcum geophilum Fr., one of several ectomycorrhizal species associated with black pine (Pinus thunbergii Parl.), is dominant in the coastal forests of Japan, even under adverse abiotic environmental conditions. In these forests, many tonnes of Sumipine® (fenitrothion) are applied every year to protect P. thunbergii from pine wilt disease, which is transmitted by a beetle. Here, we examined the effect of this insecticide on the species of fungi found as ectomycorrhizae on naturally regenerated P. thunbergii seedlings collected from coastal forest sites that had or had not been sprayed with fenitrothion. The proportion of C. geophilum ectomycorrhizae on black pine root tips was significantly higher in areas where fenitrothion had been applied than in areas where it had not. We measured the in vitro mycelial growth of C. geophilum as well as other ectomycorrhizal fungi of coastal black pine, Rhizopogon roseolus (Corda) Th. Fr. and Pisolithus arhizus (Scop.) Rauschert, at three levels of fenitrothion (density: 1.32 g/cm³), i.e., 0, 0.1 and 0.2 mL L^?1. The growth of all three species decreased significantly as the fenitrothion dosage increased. However, the reduction of mycelial growth in response to fenitrothion was lower in C. geophilum than in the other two species. These results suggest that C. geophilum has a high tolerance for fenitrothion, which may explain its dominance over other ectomycorrhizal species in coastal forests in Japan where fenitrothion is routinely sprayed.

     

Effects of increasing saturation vapour pressure deficit on growth and ABA levels in black spruce and jack pine

 Plant responses to saturation vapour pressure deficit (SVPD) were studied by subjecting black spruce [Picea mariana (Mill) B.S.P.] and jack pine seedlings (Pinus banksiana Lamb.) to humid (0.3 – 0.8 kPa) or dry (2.0 – 2.5 kPa SVPD) regimes for 4 weeks using a computer-controlled environmental system to control diurnal variation in SVPD. Dry matter accumulation in needles was not altered by increasing SVPD. However, root growth declined by 60% which increased shoot to root ratio and reduced total seedling dry weight in both black spruce and jack pine. Relative growth rate of jack pine also declined to about half the rate of plants grown under humid conditions. In situ root marking studies showed that the decline in root growth of jack pine under the high SVPD was the result of reduced lateral root initiation, whereas root elongation was unaffected by humidity. A 4-week exposure to dry air increased abscisic acid (ABA) levels in needles, but not roots, of jack pine whereas ABA levels in black spruce were not altered. A short (3-day) exposure failed to increase needle ABA levels in either species. These results suggest that the responses of conifers to dry air were not the result of ABA accumulation. Received: 24 March 1996 / Accepted: 30 May 1996     

Aluminum-mycorrhizal interactions in the physiology of pitch pine seedlings

Aluminum (Al) in the rhizosphere adversely affects plant nutrition and growth. Although many conifer species, and pitch pine (Pinus rigida) in particular, have evolved on acidic soils where soluble Al is often high, controlled environment studies often indicate that Al interferes with seedling growth and nutrient relations. Under normal field conditions, conifer roots grow in a symbiotic relationship with ectomycorrhizal fungi, and this association may modulate the effects of Al on root physiology. To investigate the influence of mycorrhizal infection on Al toxicity, pitch pine seedlings were grown with or without the ectomycorrhizal symbiont Pisolithus tinctorius and were exposed to low levels of Al in sand culture. Aluminum at 50 μM reduced nonmycorrhizal seedling growth and increased foliar Al concentrations, but did not alter photosynthetic gas exchange or other aspects of seedling nutrition. Nonmycorrhizal seedlings exposed to 200 μM Al exhibited decreased growth, increased transpiration rates, decreased water use efficiency, increased foliar Al and Na levels, and reduced foliar P concentrations. Seedlings inoculated with P. tinctorius exhibited unaltered growth, physiological function, and ionic relations when exposed to Al. The fungal symbiont evidently modulated ionic relations in the rhizosphere, reducing Al-P precipitation reactions, Al uptake, and subsequent root and shoot tissue Al exposure.     

Growth,nutrient acquisition and ectomycorrhizae of <Emphasis Type="Italic">Eucalyptus regnans</Emphasis> F. Muell. seedlings in fertilized or diluted air-dried and undried forest soil

Seedlings of Eucalyptus regnans (mountain ash) grow poorly in undried forest soil, where they develop purple coloration in the foliage, but their growth is markedly improved when forest soil has been air dried. Whether this growth promotion is purely due to improved nutrient status of the soil, as a result of air drying, was investigated. In several pot experiments, E. regnans seedlings were grown (i) in air-dried and undried forest soil with addition of different levels of complete fertiliser, (ii) in air-dried or undried soil diluted to different extents with sand, or (iii) in undried soil mixed with different amounts of air-dried soil. Seedling dry weight, P content and incidence of ectomycorrhizal root tips were determined.In all experiments, the dry weights of seedlings were 3–6 times greater in 100% air-dried soil than in 100% undried soil. Fertiliser application resulted in a significant increase in dry weight of seedlings in both air-dried and undried soil, but the dry weights in air-dried soil were always significantly greater than those in undried soil at the same level of fertiliser application. Even at the highest level of fertiliser application, the growth difference between seedlings in air-dried and undried soil remained. When air-dried soil was diluted with sand, there was a significant reduction in seedling dry weight only when soil was diluted to 20% or less (air-dried soil:total mix). Conversly, when air-dried soil was mixed with undried soil, there was a proportional decrease in seedling dry weight with increasing amounts of undried soil. In all experiments, the dominant ectomycorrhizal morphotypes in 100% air-dried soil were different from those in undried soil. Fertilisation and dilution of air-dried and undried soil did not result in a reduction in the overall incidence of ectomycorrhizal root tips, although the frequency of occurrence of different ectomycorrhizal morphotypes was affected.It is concluded that the growth difference between seedlings in air-dried and undried forest soils is not due solely to differences in the direct availability of nutrients in the soils, and different ectomycorrhizae may indirectly affect nutrient availability to the plant.     

The feeding preference of mycophagous Collembola varies with the ectomycorrhizal symbiont

The interactions of the collembolan insect Proisotoma minuta with ectomycorrhizal and/or pathogenic fungi was examined in three experiments: (1) in vitro analysis of feeding patterns, (2) in vitro food preference test, and (3) in situ analysis of ectomycorrhizal colonization in relation to population density. The ectomycorrhizal fungi Laccaria laccata, Pisolithus tinctorius, Suillus luteus, Thelephora terrestris and the pathogenic fungi Rhizoctonia solani were employed in all experiments. In vitro and in situ experiments revealed that Pr. minuta consumed all the ectomycorrhizal fungi tested but the feeding pattern and consumption varied with each isolate. In a comparative in vitro feeding preference test, where Pr. minuta was given a choice, R. solani was grazed more heavily than the ectomycorrhizal fungi. Among the ectomycorrhizal fungi examined, Pi. tinctorius was consumed significantly less than L. laccata, S. luteus or T. terrestris in the presence of R. solani. A 10-week in situ analysis of loblolly pine (Pinus taeda L.) seedling root systems inoculated with Pr. minuta revealed that ectomycorrhizal colonization was significantly less than that of control plants (without Pr. minuta). Collectively, these data suggest that mycophagous Collembola may play a major role in the distribution and biomass of ectomycorrhizal fungi in the rhizosphere of tree seedlings.     

松萎蔫病发生区和未发生区油松根部真菌群落研究

植物根部真菌群落结构和多样性与植物的抗病性和病害的危害程度相互影响。为揭示松萎蔫病与松树根部真菌群落的相互作用,该研究对陕西省商洛市柞水县松萎蔫病发生区和未发生区油松的根尖活性、根部外生菌根真菌(ECMF)和深色有隔内生真菌(DSE)的侵染率进行分析,并通过油松根部可培养真菌的分离和鉴定,分析了两地油松根部真菌的群落结构及多样性。结果显示:(1)松萎蔫病未发生区油松根部的活性根尖比、菌根根尖比和ECMF的侵染率均显著高于发生区,而DSE的侵染率和微菌核密度却低于松萎蔫病发生区,ECMF的侵染率在两个样区油松根部都显著高于DSE。(2)从两个样区油松根部共分离到131个菌株,根据形态和分子学特征最终鉴定为23种真菌,其中DSE占绝对优势,且Phialocephala fortinii和Cryptosporiopsis ericae为油松根部分离真菌的优势种。(3)两个样区真菌的群落组成存在明显差异,共有真菌仅5种。(4)松萎蔫病未发生区真菌群落的丰富度(17)和多样性(2.012 0)、以及ECMF的相对丰度(8%)都高于松萎蔫病发生区(分别为11、1.197 9和1.6%),而DSE的相对丰度(70%)却明显低于发生区(82.7%)。研究表明,松萎蔫病的发生影响了油松根部的活性、菌根的形成、ECMF和DSE的侵染,以及根部真菌的群落组成和多样性。该文首次报道了DSE与松萎蔫病的关系,但分离真菌对油松松萎蔫病抗性的影响有待进一步研究。     

Suillus variegatus causes significant changes in the content of individual polyamines and flavonoids in Scots pine seedlings during mycorrhiza formation in vitro

Changes in the concentrations of individual flavonoids and polyamines (PAs) in Scots pine (Pinus sylvestris L.) cotyledonary seedlings were studied during the establishment of an ectomycorrhizal (ECM) symbiosis with two Suillus variegatus strains in vitro. Both flavonoids and PAs were analysed after 3, 7, and 14 d in dual culture, and changes in concentrations were compared with growth of the seedlings. Both S. variegatus strains caused similar responses in Scots pine seedlings. Free putrescine accumulated immediately but only transiently after inoculation. This was followed by continuous accumulation of PA conjugates in needles and stems, and free spermidine and spermine in roots, which was accompanied by mycorrhiza formation and improved growth. The fungi induced lateral root formation and main root and primary needle elongation. Inoculation caused no qualitative changes in flavonoid composition, while quantitative changes in flavonols, catechins, and condensed tannins were observed in shoots during mycorrhiza formation. These results indicate that in this in vitro system conjugated PAs and specific flavonoids, generally related to the plant's defence reactions, did not play a major role in the regulation of the establishment of the ectomycorrhizal (ECM) symbiosis in Scots pine roots. The results also clearly show that positive growth responses in shoots and roots due to S. variegatus were supported by different and highly specific changes in the synthesis of both primary and secondary metabolites in these parts of the seedling.     

外生菌根菌对油松幼苗抗氧化酶活性及根系构型的影响

研究盆栽条件下,接种褐环乳牛肝菌(Suillus luteus)和红汁乳菇(Lactarius hatsudake)对油松(Pinus tabulaeformis)苗木生长,抗氧化酶活性和根系构型的影响。结果表明:(1)褐环乳牛肝菌和红汁乳菇均可与油松合成外生菌根,并显著提高苗木的苗高、地径、鲜重和干重。(2)接种褐环乳牛肝菌苗木针叶抗氧化酶(SOD、CAT、POD)活性分别比接种红汁乳菇苗木高14.77%、20.77%、34.68%;接种褐环乳牛肝菌苗木根系抗氧化酶(SOD、CAT、POD)活性分别比接种红汁乳菇苗木高8.54%,4.34%,33.31%;接种处理苗木抗氧化酶活性均显著高于不接种处理。接种处理苗木根长、表面积、体积、平均直径、根尖数、分叉数显著高于不接种处理;接种处理间苗木只有根尖数存在显著差异;接种褐环乳牛肝菌的油松根系分支成80°—90°的一级侧根数占23.81%,显著多于接种红汁乳菇和对照苗木。研究表明,接种褐环乳牛肝菌和红汁乳菇均能促进油松苗木生长,提高油松体内抗氧化酶活性,扩大苗木根系的吸收范围,其中褐环乳牛肝菌各方面的促进效果要优于红汁乳菇。     

外生菌根菌不同接种方法对樟子松苗木生长的影响

 以提高外生菌根真菌对樟子松(Pinus sylvestris var. mongolica)苗木促生长效果为目的, 在前期研究的基础上, 采用菌株配对培养的方法对获得的樟子松外生菌根真菌进行混合接种菌株组合筛选; 采用苗木截根-菌液浸根和沟施接种方法分别对2年生和3年生樟子松苗木进行野外单接种及混合接种。研究外生菌根真菌不同接种方法、菌株单接种及混合接种对樟子松苗木生长的影响。试验结果表明: 供试菌株及菌株组合对樟子松苗木生长均有一定的促进作用。菌株GT005和菌株035为供试菌株中对樟子松苗木促生长效果最佳的菌株。采用苗木截根-菌液浸根方法接种2年生樟子松苗木130 d, GT005接种的苗木高生长提高54%, 地径生长提高15%, 过氧化氢酶活性提高48%, 而根系活力降低3%; 菌株035接种的苗木高生长提高42%, 地径生长提高56%, 过氧化氢酶活性提高47%, 根系活力提高11%。沟施接种方法接种3年生樟子松苗木100 d, GT005接种苗木高生长提高10%, 地径生长提高15%, 过氧化氢酶活性提高90%, 而根系活力降低34%; 菌株035接种苗木高生长提高7%, 地径生长提高9%, 过氧化氢酶活性提高6%, 而根系活力降低46%; 菌株组合044/GT001和GT001/GT005 接种的苗木高生长仅比对照提高3.47%和2.07%, 而菌株组合 044/025 和044/009 接种的苗木高生长低于对照; 混合接种的苗木其地径生长高于对照0.16%～7.98%。综上所述, 苗木截根-菌液浸根接种方法对苗木的促生长效果显著高于沟施接种方法; 外生菌根菌高效菌株与一般菌株混合接种会弱化高效菌株自身接种效果; 苗木过氧化氢酶活性、苗木根系活力与苗木的生物量间无相关性。     

The survival and development of inoculant ectomycorrhizal fungi on roots of outplanted Eucalyptus globulus Labill

The survival and development of two inoculant ectomycorrhizal fungi (Hebeloma westraliense Bough. Tom. and Mal. and Setchelliogaster sp. nov.) on roots of outplanted Eucalyptus globulus Labill. was examined at two expasture field sites in the south-west of Western Australia. Site 1 was a gravelly yellow duplex soil, and Site 2 was a yellow sandy earth. Plants were grown in steamed or unsteamed soil, in root bags designed as field containers for young growing trees. Three, 6 and 12 months after outplanting, plants were removed from these bags and assessed for dry weights of shoots and ectomycorrhizal colonization of roots.The inoculant ectomycorrhizal fungi (identified on the basis of the colour and morphology of their mycorrhizas) survived on roots of E. globulus for at least 12 months after outplanting at both field sites. At Site 1, however, colonization of new fine roots by the inoculant fungi was low (less than 20% of fine root length). Inoculation had no effect on the growth of E. globulus at this site. In contrast, at Site 2 the inoculant ectomycorrhizal fungi colonized up to 30–50% of new fine root length during the first 6 months after outplanting. There was a corresponding growth response to ectomycorrhizal inoculation at this site, with a close relationship (r²=0.82^**) between plant growth at 12 months and root colonization at 3 months. Plant growth at 12 months was related less closely with root colonization at 6 or 12 months. Root colonization by resident ectomycorrhizal fungi increased with time at both field sites. At Site 2, this increase appeared to be at the expense of colonization by the inoculant fungi, which was reduced to less than 10% of fine root length at 12 months. Steaming the soil had little effect on colonization by the inoculant ectomycorrhizal fungi at either field site, but decreased colonization by the resident ectomycorrhizal fungi.     

接种彩色豆马勃对模拟酸沉降下马尾松幼苗生物量的影响

外生菌根能够提高宿主植物对外界环境胁迫的抵抗力,促进植物的生长,本文试图揭示外生菌根对酸雨胁迫下马尾松生长的保护作用。本研究采用盆栽试验,共设置四个处理：酸雨对照处理（Control check (CK), 约pH值5.5）不接种,酸雨对照处理接种,酸雨pH值3.5处理不接种,酸雨pH值3.5处理接种。pH值3.5的酸雨处理降低马尾松的生物量,在试验前期降低根冠比,试验中后期则提高根冠比,在试验初期增加了叶面积,但中后期显著降低了叶面积。接种外生菌根菌有利于马尾松幼苗的生长,pH值3.5处理下接种外生菌根菌能提高马尾松幼苗的生物量,外生菌根菌对生物量分配和叶面积的影响与酸雨胁迫的影响是相反的,即外生菌根菌抵消了酸雨胁迫对马尾松的影响。