Number Of Mycorrhizal Root Tips Research Articles

Chemical and morphological response of beech saplings (Fagus sylvatica L.) to an experimental soil drought gradient

European beech (Fagus sylvatica L.) is a common tree species in Central European forests but the fitness of this species under future climate conditions is still a matter of debate. Here, we study the response of transplanted beech saplings in terms of their chemical and morphological traits to different levels of soil drought in a mountainous, partially open, storm damaged Norway spruce forest. Throughfall was excluded by roof constructions in three consecutive growing seasons. Spatial soil drought gradients resulted from soil water consumption by heterogeneously distributed mature spruce trees. Individual drought stress dose (DSD) was assessed for each beech sapling using cumulative soil matric potential in the rooting zone. After three years of drought treatment, we analyzed biomass components, traits of leaves and fine roots of sixty beech saplings. In the third year, the classical permanent wilting point in the soil was exceeded for some beech saplings, however, all saplings survived the drought treatments. Several chemical plant traits responded to DSD sum of the last two years, while morphological traits and biomass components were mostly not or weakly correlated with DSD. Potassium concentration and associated C:K and N:K ratios in fine roots were most sensitive to drought stress. We assume that K and other nutrients were hardly available in the extremely dry forest floor and that the undersupply could not be compensated by nutrient uptake from the mineral soil. Increasing C concentration in leaves indicates an acclimation towards sclerophylly to maintain the hydraulic function of leaves. Increasing specific root length (SRL), specific root tip density (SRTD) and decreasing fine root diameter also indicate a morphological acclimation of saplings to increasing DSD. Weak correlations between morphological traits and DSD partly resulted from non-linear responses to increasing DSD. Maximum number of mycorrhizal root tips and maximum fine root biomass occurred at medium DSD. Our results suggest that the acclimation of chemical and morphological traits fortifies the resilience of beech saplings against soil drought in the years after transplantation. However, reduced uptake of soil nutrients caused by drought can only be partially compensated by redistribution within the sapling. An expansion of the rooting zone in the moist, nutrient-poor subsoil can improve the water uptake of beech saplings during drought periods, but this strategy hardly improves their nutrient supply.

Effect of inoculation with putative plant growth-promoting rhizobacteria isolated fromPinusspp. onPinus pineagrowth, mycorrhization and rhizosphere microbial communities

In this study, 10 putative plant growth-promoting rhizobacteria (PGPR) were assayed for their ability to improve Pinus pinea growth and mycorrhization. After an inoculation assay, except for two, all strains stimulated plant growth. All bacteria altered rhizosphere microbial communities as revealed by phospholipid fatty acid analysis; associating plant growth promotion with a decrease in biological diversity. Three strains were tested for their ability to enhance pine mycorrhization with wild fungi species. Only strain BB1 increased the total number of mycorrhizal root tips. Mycorrhizas present in the roots of each treatment were identified by ribosomal RNA sequencing and denaturing gradient gel electrophoresis analysis, detecting specificity between mycorrhizal species colonizing the roots and the inoculated PGPR. In conclusion, BB1 appears to be a good candidate to be developed into a biofertilizer directed to enhance pine growth and mycorrhization, which should result in a better establishment rate for plants used in reforestation. This study shows the potential of PGPR to improve fitness of forest tree specie. Moreover, the specificity between the bacteria inoculated and the mycorrhiza that the plant selects involve a potential biotechnological use in production of value-added fungi.

Effects of Fertilization with Dolomite Lime+PK or Wood Ash on Root Distribution and Morphology in a Norway Spruce Stand in Southwest Sweden

Abstract Pelleted wood ash (A) or crushed dolomite lime with added potassium and phosphorous (CaMgPK) was applied to plots in a 60-yr-old Norway spruce stand in Southwest Sweden. Eight years later, we measured the effect of these treatments on a number of root parameters, including root biomass and distribution (in different diameter classes), root length density (cm cm-3 soil), specific root length (SRL, m g-1 DM), and number of mycorrhizal root tips. Layers sampled included the humus layer and the upper 30 cm of the mineral soil. The total fine root (0–1 mm) biomass in the mineral soil layer was lower in the A plots than the control plots, and the fine root (1–2 mm) systems were shallower in the A plots compared to both the control and CaMgPK plots. SRL was higher in the humus layer in both the CaMgPK and A plots than in the controls, and higher in the CaMgPK than in the A plots. The number of mycorrhizal root tips was also higher in the treated plots than in the controls, with the highest numbers being found in CaMgPK plots. Based on our results, we conclude that both the CaMgPK and ash treatments resulted in changes in root morphology and, therefore, presumably increased the capacity for nutrient uptake. FOR. SCI. 50(6):802–809.

The ectomycorrhizal symbiosis between Lactarius deliciosus and Pinus sylvestris in forest soil samples: symbiotic efficiency and development on roots of a rDNA internal transcribed spacer-selected isolate of L. deliciosus.

The effect on plant growth of pre-inoculation of Pinus sylvestris with the ectomycorrhizal (ECM) edible basidiomycete Lactarius deliciosus (isolate D45) under controlled conditions, and the development on roots of this basidiomycete, were investigated in gamma-irradiated and unsterilized containers containing different forest soil cores or a perlite-vermiculite mixture. Five months after planting, L. deliciosus mycorrhizal plants exhibited greater growth than the non-mycorrhizal ones in all soil types, i.e. up to a 325% increase in shoot height in the sterilized soils. The experiment demonstrated the dependency of P. sylvestris seedlings upon ECM symbiosis for their survival in gamma-irradiated, microbiologically disturbed soil samples. Furthermore, in two soils, the growth of L. deliciosus-inoculated seedlings was greater in the sterilized soil samples than in the non-sterilized ones, i.e. 46% and 132% increase in shoot height under sterilized soil conditions. In containers randomly sampled from each soil type, the degree of root colonization by the inoculated isolate, calculated as the number of mycorrhizal root tips divided by the total number of root tips x100, ranged from 80% to 35%. Within the short term, the inoculated isolate developed rapidly on roots, dominated, and hampered ectomycorrhiza formation by various unidentified (but not Lactarius) resident ECM fungi in unsterilized soil types. Results indicate that the ECM species L. deliciosus is worth investigating to ascertain if other isolates benefit pine growth like the isolate D45, and are therefore also attractive candidates for forestry applications in the Mediterranean area.

Changes in fine root production and longevity in relation to water and nutrient availability in a Norway spruce stand in northern Sweden.

Effects of irrigation and liquid fertilization on fine root (< 1 mm) production and longevity, and fine root (< 0.5-2 mm) biomass were studied in a Norway spruce (Picea abies (L.) Karst.) stand in northern Sweden. Fine root length production and longevity were measured by the minirhizotron technique at 0-10 cm depth in the following treatments: irrigation (I), liquid fertilization (IL) and control (C). Standing root biomass and root length density (RLD) were studied in the litter-fermented humus (LFH) layer and at depths of 0-10, 10-20 and 20-30 cm using soil cores in solid fertilized (F) and C plots. Minirhizotrons were installed in October 1994 and measurements recorded monthly from July to September 1995 and during the growing season in 1996. Soil cores were sampled in 1996. Fine root production increased significantly in IL plots compared with C plots, but the I treatment did not increase root production. Root mortality increased significantly in IL plots compared with C plots. Fine root longevity in IL plots was significantly lower compared with C and I plots. No significant difference was found between longevity of fine roots in I and C plots. Compared with C, F treatment increased fine root biomass in the LFH and mineral soil layers, and increased the amount of fine roots in mineral soil layers relative to the LFH layer. Furthermore, F increased RLD and the number of mycorrhizal root tips significantly.

Characterizing the Size Dependence of Resource Acquisition within Crowded Plant Populations

We present and apply a method for analyzing size-dependent patterns of resource acquisition by individuals within stands of competing plants. Our approach relies on curve-fitting to relate empirical measures of resource acquisition with various aspects of plant size and form. These relationships are referred to as size–uptake relationships (SURs). We demonstrate the use of this approach by characterizing the size dependence of light and nitrogen acquisition within developing stands of birch seedlings. Results of a number of phenomenological studies have predicted that competition for light is expected to be size asymmetric and that competition for belowground resources is expected to be size symmetric. Our study provides the first direct empirical test for these hypotheses. Application of the SUR approach largely confirms predictions regarding the size-dependent nature of light and belowground resource (nitrogen) acquisition. The uptake of nitrogen by birch seedlings was size symmetric, regardless of which aspect of size we considered (i.e., root mass, root length, root surface area, number of root tips, number of mycorrhizal root tips). In contrast, light interception was size asymmetric in relation to height and leaf area, but size symmetric in relation to total plant biomass. Differences in the degree of size-asymmetry of light acquisition between different measures of size were driven by the nature of the allometric relationships between plant height, biomass, and leaf area. SURs offer a tool for exploring some of the mechanistic processes related to resource-based interactions. Using this approach, we demonstrate that it is possible to characterize simultaneously the size-dependent patterns of multiple resources within competing plant populations. We suggest that this approach may prove valuable for identifying how size-dependent patterns of resource acquisition vary through ontogeny. We conclude with a discussion of the need for a more mechanistic understanding of plant–plant interactions and the role that the SUR approach can play towards this goal.

Plant and fungal responses to elevated atmospheric CO 2 in mycorrhizal seedlings of Betula pendula

The effects of elevated CO 2 concentrations upon carbon allocation in mycorrhizal (M) and non-mycorrhizal (NM) birch ( Betula pendula) seedlings were investigated. M plants, colonised by the fungus Paxillus involutus, and NM plants, were exposed for 3 months to ambient (350 μl l −1) or elevated (700 μl l −1) CO 2 environments. The assimilation and distribution of carbon within the different compartments of the plant–substrate–fungal system were investigated using radioactive carbon as a tracer. In addition, the impact of elevated CO 2 upon extension growth of the ectomycorrhizal mycelium of the fungus was determined in transparent observation chambers. Yields of whole plants and of shoots were significantly decreased under elevated CO 2 whether they were grown with or without their fungal symbionts. Neither the dry mass production of roots of mycorrhizal plants, nor the amount of carbon allocated to shoots, roots and mycorrhizal tips were affected by elevated CO 2. While the number of mycorrhizal root tips was decreased with CO 2 enrichment, their relative importance in the total root system was unchanged. There was a significant increase in the extent of development of the external mycelium under elevated CO 2. A greater proportion of the radioactive carbon was allocated to the soil compartment under elevated CO 2. This increase, probably arising through increased rhizodeposition, was greater in NM than M plants. The responses are discussed in terms of nutrient availability in the growth media and the possible role of increased carbon allocation to mycorrhizal mycelium in nature.

Some Effects of N on Ectomycorrhizal Diversity of Scots Pine ( Pinus sylvestris L.) in Northeastern Germany

In the last three decades high industrial nitrogen (N) emissions have led to eutrophication of a Scots pine stand (Pinus sylvestris [L.]) near Schwedt characterized by a broad cover of Calamagrostis epigejos [L.] Roth (Poaceae). In comparison to the relatively unimpacted control site (low N site), this high N site showed a remarkably low mycorrhizal frequency (percentage of mycorrhizas on total amount of root tips) with seasonal lows down to 27 %. At the low N site the highest number of mycorrhizal root tips was found in the organic layer. At the high N site the amount of mycorrhizas per soil volume was similar in both organic and mineral soil layers, and also significantly lower when compared to the amount at the low N site. The high N site revealed only nine mycorrhizal morphotypes instead of eighteen found at each sampling date at the control site. 80 % of the coenosis at the high N site were represented by only four morphotypes resulting in a low diversity. The seasonal decrease in the mycorrhizal frequency, the small amount of mycorrhizas and the low diversity suggest that the high N deposition at this site has reduced the ability of the pine trees to withstand natural stresses such as prolonged drought or frost periods. This corresponds well with the 42 % reduction in tree stocking density at the high N site compared to the low N site.

Ectomycorrhizae of Young and Mature Scots Pine Trees in Industrial Regions in Poland

Ectomycorrhizae are obligate symbiotic structures of forest tree roots and are susceptible to environmental changes. Ectomycorrhizae of Scots pine ( Pinus sylvestris L.) trees grown in forests influenced by different levels of air pollutants were investigated. Total numbers of mycorrhizal root tips in the soil horizons and the frequency of mycorrhizal morphotypes were studied as indicators of ectomycorrhizal status. The studies were conducted in two comparable young plantations in western Poland with high and low pollution exposure and in two mature forest ecosystems in southern Poland differing in pollution exposure. At the young Scots pine plantation with high pollution exposure (Luboń), numbers of mycorrhizal root tips in the soil layer 0–5 cm were lower during three growing seasons than at the cleaner site (Kórnik). In the soil layer 15–30 cm the total number of mycorrhizal root tips was found slightly higher at the polluted than at the control site. There was no difference in the frequency of the seven mycorrhizal morphotypes found at the two young plantations. At the heavily polluted mature forest stand (Niepołomice Forest) the total number of mycorrhizal root tips was lower in zones of severe pollution levels than in the less polluted zones. Moreover, the average number of mycorrhizae in the Niepołomice Forest was lower than in the moderately polluted forest ecosystem (Ratanica catchment). The mycorrhizal diversity of the mature pines in the heavily polluted forest was reduced (four morphotypes) as compared to the moderately polluted forest (eight morphotypes). The relationship between industrial pollution and mycorrhizal status was more pronounced at the mature Scots pine stands than at the young plantations.

Pine and spruce seedling growth and mycorrhizal infection after inoculation with plant growth promoting Pseudomonas strains

Pine and spruce seeds were inoculated with antibiotic-resistant plant growth promoting fluorescent Pseudomonas strains Sm3-RN, Ss2-RN and Sw5-RN for evaluation of bacterial root colonization and seedling growth responses under greenhouse conditions. Mycorrhizal inoculum was introduced to seedling containers by placing 2 cc of forest floor soil around seeds at the time of sowing. Mycorrhizal roots were detected on 39% of pine and 30% of spruce seedlings treated with forest soil 13–15 weeks later. Most mycorrhizae were formed by Wilcoxina sp. (E-strain) (89% for spruce and 69% for pine); some Amphinema-like, Mycelium radicis atrovirens, Suillus-like, Thelephora-like, and Tuber-like mycorrhizae were also detected. In the absence of bacterial inoculum, spruce seedling biomass was positively correlated with the number of mycorrhizal root tips. This trend was obscured following inoculation with strains Ss2-RN and Sw5-RN. Pine seedling growth was weakly correlated with mycorrhizal root tip development only after treatment with strain Sm3-RN. Bacterial inoculation did not influence the mycorrhizal status of seedlings, but all three Pseudomonas strains stimulated biomass accumulation of spruce and pine seedlings, up to 19% (P < 0.05). Non-mycorrhizal seedlings tended to support smaller root-associated Pseudomonas populations, but inoculant bacteria colonized seedlings with a minimum of 6.3 × 103 colony forming units per gram of rhizosphere soil regardless of their mycorrhizal status. For spruce, growth effects due to bacterial inoculation were similar in both mycorrhizal and non-mycorrhizal seedlings. However, statistically significant gains in pine biomass by inoculation with strains Sm3-RN and Ss2-RN occurred only in mycorrhizal seedlings, whereas strain Sw5-RN caused significant growth promotion only in non-mycorrhizal pine. Our results suggest that these fluorescent pseudomonad strains enhanced spruce seedling growth through mechanisms unrelated to increased mycorrhizal colonization, but growth promotion of pine by strains Sm3-RN and Ss2-RN was facilitated by an interaction with mycorrhizae.

Pine and spruce seedling growth and mycorrhizal infection after inoculation with plant growth promoting Pseudomonas strains

Pine and spruce seeds were inoculated with antibiotic-resistant plant growth promoting fluorescent Pseudomonas strains Sm3-RN, Ss2-RN and Sw5-RN for evaluation of bacterial root colonization and seedling growth responses under greenhouse conditions. Mycorrhizal inoculum was introduced to seedling containers by placing 2 cc of forest floor soil around seeds at the time of sowing. Mycorrhizal roots were detected on 39% of pine and 30% of spruce seedlings treated with forest soil 13–15 weeks later. Most mycorrhizae were formed by Wilcoxina sp. (E-strain) (89% for spruce and 69% for pine); some Amphinema-like, Mycelium radicis atrovirens, Suillus-like, Thelephora-like, and Tuber-like mycorrhizae were also detected. In the absence of bacterial inoculum, spruce seedling biomass was positively correlated with the number of mycorrhizal root tips. This trend was obscured following inoculation with strains Ss2-RN and Sw5-RN. Pine seedling growth was weakly correlated with mycorrhizal root tip development only after treatment with strain Sm3-RN. Bacterial inoculation did not influence the mycorrhizal status of seedlings, but all three Pseudomonas strains stimulated biomass accumulation of spruce and pine seedlings, up to 19% ( P < 0.05). Non-mycorrhizal seedlings tended to support smaller root-associated Pseudomonas populations, but inoculant bacteria colonized seedlings with a minimum of 6.3 × 10 3 colony forming units per gram of rhizosphere soil regardless of their mycorrhizal status. For spruce, growth effects due to bacterial inoculation were similar in both mycorrhizal and non-mycorrhizal seedlings. However, statistically significant gains in pine biomass by inoculation with strains Sm3-RN and Ss2-RN occurred only in mycorrhizal seedlings, whereas strain Sw5-RN caused significant growth promotion only in non-mycorrhizal pine. Our results suggest that these fluorescent pseudomonad strains enhanced spruce seedling growth through mechanisms unrelated to increased mycorrhizal colonization, but growth promotion of pine by strains Sm3-RN and Ss2-RN was facilitated by an interaction with mycorrhizae.

Effect of Plant Growth Promoting BacillusStrains on Pine and Spruce Seedling Growth and Mycorrhizal Infection

Rifamycin-resistant derivatives of plant growth promoting Bacillus polymyxastrains L6, Pw-2, and S20 were used to evaluate the interaction of bacterial–mycorrhizal co-inoculation on pine and spruce seedling growth. We were particularly interested in determining if the mechanism by which bacteria stimulated seedling growth depended on the presence of ectomycorrhizae. Mycorrhizal inoculum was introduced by adding 2ml of one of six forest floor soil types originating from different spruce and pine stands to seedling containers. Mycorrhizal roots developed in 34% of pine and 27% of spruce seedlings treated with forest soil, but no differences between forest soils were detected. Most mycorrhizae were formed by Wilcoxinasp. (E-strain) (98% for spruce and 67% for pine); small numbers of Amphinema-like, Mycelium radicis atrovirens, Suillus-like, Thelephora-like, and Tuber-like mycorrhizae were also found on pine (27% in total). Thelephora-like fungi comprised 2% of spruce mycorrhize. In the absence of bacterial inoculum, spruce seedling biomass was positively correlated with the number of mycorrhizal root tips, but this trend was not detected in spruce inoculated with bacteria or in pine. Bacterial inoculation did not influence the mycorrhizal status of seedlings, but all three Bacillusstrains stimulated growth of both conifer species. Root biomass, in particular, was significantly enhanced by up to 18% compared with uninoculated controls. Mycorrhizal fungi improved the growth of spruce seedlings, but plant growth promotion by Bacilluswas similar for mycorrizal and non-mycorrhizal seedlings of both species. Our results suggest that Bacillusstrains L6-16R, Pw-2R, and S20-R enhance conifer seedling growth through a mechanism unrelated to mycorrhizal fungi.

Effect of artificial defoliation on biomass allocation in ectomycorrhizal Pinussylvestris seedlings

Ectomycorrhizal seedlings of Scots pine (Pinussylvestris L.) were subjected to repeated artificial defoliation (0, 25, 50, and 75%) to demonstrate the effect of a reduced amount of photosynthates on the allocation of biomass between the tree and its fungal symbionts. Defoliation reduced shoot biomass in the seedlings significantly, and belowground parts adjusted to the same growth level. Biomass parameters of seedlings that had undergone the mildest defoliation treatment did not differ significantly from control seedlings, while the two most intensive treatments reduced growth and biomass of seedlings in a similar way. Defoliation did not reduce mycorrhizal colonization or fungal biomass calculated per unit weight of fine roots. Actual needle biomass in seedlings correlated positively with stem biomass, total root biomass, fungal biomass both in roots and in soil, and the number of mycorrhizal root tips per seedling. Root/shoot ratio and total allocation pattern were relatively constant.

Influence of aluminum on in vitro formation of Pinus caribaea mycorrhizae

The ability of Pinus caribaea var. hondurensis to form mycorrhizae was determined in vitro with seven species of ectomycorrhizal fungi in the presence of six levels of Al (added as AlCl3) in a nutrient solution. The time required for mycorrhizal formation, the number of mycorrhizal root tips and the percent mycorrhizae were measured after 15, 30, 60, 90 and 120 days. Cenococcum graniforme was susceptible to Al toxicity at all Al concentrations. Pisolithus tinctorius and Suillus sp. were depressed at lower but stimulated at higher Al concentrations. The inverse was shown for Rhizopogon reaii and Hebeloma cylindrosporum. Tolerance to Al was verified for R. nigrescens and H. crustuliniforme. Pisolithus tinctorius had the largest mycorrhizal capacity, defined as the sum of the values for time, percent and number of mycorrhizae. Ectomycorrhizal fungi appeared to ameliorate Al damage to plant roots even in treatments where no mycorrhizae formed. Inoculation of pine seedlings with Al-tolerant mycorrhizal fungi is likely to improve reforestation efforts in highly-weathered tropical soils.

Interaction effects of vegetation type and Pacific madrone soil inocula on survival, growth, and mycorrhiza formation of Douglas-fir

Douglas-fir seedlings were planted in cleared blocks within three adjacent vegetation types, whiteleaf manzanita, annual grass meadow, and an open stand of Oregon white oak, in southwest Oregon. Within subplots in each block, either pasteurized or unpasteurized soil from a nearby Pacific madrone stand was transferred to the planting holes of the seedlings; control seedlings received no madrone soil. Second-year survival averaged 92, 43, and 12% for seedlings planted on the manzanita, meadow, and oak sites, respectively. Growth differences generally paralleled survival differences. Added madrone soil, whether pasteurized or unpasteurized, did not influence survival, but growth of seedlings on the manzanita site was substantially increased by the addition of unpasteurized madrone soil. Unpasteurized madrone soil did not influence growth of seedlings in the meadow and the oak stand. Pasteurized madrone soil did not affect growth in any of the vegetation types. When added to the manzanita site, unpasteurized madrone soil nearly tripled the number of mycorrhizal root tips forming on seedlings and resulted in formation of a new mycorrhiza type not seen otherwise. As with growth, unpasteurized madrone soil had little or no effect in the other vegetation types. These results suggest that manzanita and madrone impose on soils a biological pattern that stimulates Douglas-fir growth and survival, and they add to the growing body of literature showing that root symbionts and rhizosphere organisms mediate interactions among plant species.

THE STRUCTURE AND FUNCTION OF THE VEGETATIVE MYCELIUM OF ECTOMYCORRHIZAL PLANTS

SUMMARYUsing perspex observation chambers, the uptake, translocation and distribution of 32P‐labelled phosphorus was studied in ectomycorrhizal mycelial networks of Suillus bovinus (Fr.) O. Kuntze interconnecting plants of Pinus contorta Dougl. ex Loud and Pinus sylvestris L. Label was fed either directly to the cut ends of individual mycelial strands, to plant roots, or to the unsterile peat in the vicinity of advancing mycelial fans. Where 32P was fed to individual strands or mycelial fans it was taken up and translocated through the mycelium, over distances exceeding 40 cm, to all host plants connected to the mycelial network. Ectomycorrhizal roots acted as major sinks for phosphate but the label did not move exclusively towards the plant and was distributed throughout the mycelial system. Calculated translocation rates and flux rates suggest that transport is primarily by symplastic flow rather than turgor driven bulk flow. The amount of label accumulated by each plant was significantly related both to the size of the plant shoot and to the number of mycorrhizal root tips but did not appear to be influenced by the transpiration rates of individual plants. Phosphorus supplied directly to plant roots did not move to other plants via the mycelial connections suggesting that movement of phosphorus between the fungus and host is unidirectional.