Resource allocation in an annual herb: Effects of light,mycorrhizal fungi,and defoliation

Concurrent interactions and the availability of resources (e.g., light) affect the cost/benefit balance during mutualistic and antagonistic interactions, as well as plant resource allocation patterns. Mycorrhizal interactions and herbivory concur in most plants, where mycorrhizae can enhance the uptake of soil nutrients by plants as well as consuming a large fraction of the plant's carbon, and defoliation usually reduces light interception and photosynthesis, thereby causing direct losses to the hosts of mycorrhizal fungi. Both types of interactions affect the carbon budget of their host plants and thus we predict that the relative costs of herbivory and mycorrhizal colonization will increase when photosynthesis is reduced, for instance in light limited environments. We conducted a greenhouse experiment using Datura stramonium to investigate the effects of defoliation and mycorrhizal inoculation on the resource allocation patterns in two different light environments. Defoliated plants overcompensated in terms of leaf mass in both light environments, but total seed mass per fruit was negatively affected by defoliation in both light environments. Mycorrhizal inoculation had a positive effect on vegetative growth and the leaf nitrogen content, but defoliation negates the benefit of mycorrhizal interactions in terms of the leaf nitrogen content. In general, D. stramonium compensated for the relative costs of concurrent mycorrhizal interactions and defoliation; plants that lacked both interactions exhibited the same performance as plants with both types of interactions.     

Competition for pulsed resources: an experimental study of establishment and coexistence for an arid-land grass

In arid environments, episodically-pulsed resources are important components of annual water and nutrient supply for plants. This study set out to test whether seedlings have an increased capacity for using pulsed resources, which might then improve establishment when in competition with older individuals. A second aim was to determine whether there is a trade-off in competitive strategies when resources are supplied continuously at low concentrations, or as pulses with pronounced inter-pulse periods. A glasshouse experiment used a target-neighbour design of size-asymmetric competition, with juveniles of Panicum antidotale (blue panicgrass) introduced into contrasting densities of adult plants. Stable isotopes of nitrogen were used for measuring plant resource uptake from pulses, and tolerance to inter-pulse conditions was assessed as the mean residence time (MRT) of nitrogen. A higher root/shoot ratio and finer root system enhanced the capacity of juveniles to use resources when pulsed, rather than when continuously supplied. Higher resource uptake during pulses improved the establishment of juvenile Panicum in mixed cultures with older individuals. However, a trade-off was observed in plant strategies, with juveniles showing a lower MRT for nitrogen, which suggested reduced tolerance to resource deficit during inter-pulse periods. Under field conditions, higher utilization of pulsed resources would lead to the improved seedling establishment of Panicum adjacent to “nurse” plants, whereas mature plants with well-developed roots, exploiting a greater soil volume, maintain more constant resource uptake and retention during inter-pulse periods.     

Arbuscular mycorrhizal fungi reduce growth and infect roots of the non‐host plant Arabidopsis thaliana

The arbuscular mycorrhizal (AM) symbiosis is widespread throughout the plant kingdom and important for plant nutrition and ecosystem functioning. Nonetheless, most terrestrial ecosystems also contain a considerable number of non‐mycorrhizal plants. The interaction of such non‐host plants with AM fungi (AMF) is still poorly understood. Here, in three complementary experiments, we investigated whether the non‐mycorrhizal plant Arabidopsis thaliana, the model organism for plant molecular biology and genetics, interacts with AMF. We grew A. thaliana alone or together with a mycorrhizal host species (either Trifolium pratense or Lolium multiflorum) in the presence or absence of the AMF Rhizophagus irregularis. Plants were grown in a dual‐compartment system with a hyphal mesh separating roots of A. thaliana from roots of the host species, avoiding direct root competition. The host plants in the system ensured the presence of an active AM fungal network. AM fungal networks caused growth depressions in A. thaliana of more than 50% which were not observed in the absence of host plants. Microscopy analyses revealed that R. irregularis supported by a host plant was capable of infecting A. thaliana root tissues (up to 43% of root length colonized), but no arbuscules were observed. The results reveal high susceptibility of A. thaliana to R. irregularis, suggesting that A. thaliana is a suitable model plant to study non‐host/AMF interactions and the biological basis of AM incompatibility.     

Metal complexes increase uptake of Zn and Cu by plants: implications for uptake and deficiency studies in chelator-buffered solutions

The allocation of resources among roots and shoots represents the largest flux of resources within a plant and therefore should have been selected to maximize benefits to plants. Yet, it is unclear why some species like temperate grasses have such high root length density (RLD). Either the slow rate of diffusion of inorganic N in soils or interplant competition could explain the high RLD of temperate grasses. Using a fine-scale model of nutrient dynamics in the soil and plant growth, a cost–benefit approach was used to assess optimal allocation rates for plants that accounted for value of both carbon and nitrogen. In the absence of interplant competition, resource benefits are maximized with very little root length except in extremely dry soils for ammonium. In the presence of a competitor, optimal allocation of N to roots is much greater and increases as ability of competitors to produce root length increase. Competition for inorganic nitrogen generates a classic aspect of the tragedy of the commons, the “race for fish”, where plants must allocate more resources to acquisition of the limiting resource than is optimal for plants in the absence of competition. As such, nutrient competition needs to be directly addressed when understanding plant- and ecosystem-level resource fluxes as well as the evolution of root systems.     

Interaction between root growth allocation and mycorrhizal fungi in soil with patchy P distribution

Aims and Background

Many plants preferentially grow roots into P-enriched soil patches, but little is known about how the presence of arbuscular mycorrhizal fungi (AMF) affects this response.

Methods

Lotus japonicus (L.) was grown in a low-P soil with (a) no additional P, (b) homogeneous P (28 mg pot^?1), (c) low heterogeneous P (9.3 mg pot^?1), and (d) high heterogeneous P (28 mg pot^?1). Each P treatment was combined with one of three mycorrhiza treatments: no mycorrhizae, Glomus intraradices, indigenous AMF. Real-time PCR was used to assess the abundance of G. intraradices and the indigeneous AMF G. mosseae and G. claroideum.

Results

Mycorrhization and P fertilization strongly increased plant growth. Homogeneous P supply enhanced growth in both mycorrhizal treatments, while heterogeneous P fertilization increased biomass production only in treatments with indigenous AMF inoculation. Preferential root allocation into P-enriched soil was significant only in absence of AMF. The abundance of AMF species was similar in P-enriched and unfertilized soil patches.

Conclusion

Mycorrhization may completely override preferential root growth responses of plants to P- patchiness in soil. The advantage of this effect for the plants is to give roots more freedom to forage for other resources in demand for growth and to adapt to variable soil conditions.     

The proliferation of fungal hyphae in soils supporting mycorrhizal and non-mycorrhizal plants

This study investigated the impact of mycorrhizal plants, non-mycorrhizal plants and soil organic matter on the relative abundance of soil hyphae perceived to belong to indigenous arbuscular mycorrhizal (AM) plants. The mycorrhizal plants corn (Zea mays L.) and barley (Hordeum vulgare L.) and a non-mycorrhizal plant, canola (Brassica napus L.), were grown in unsterilized soil in pots inoculated with mycorrhizal corn root fragments. The abundance of hyphae was measured after 5 weeks and the response of fungal growth to the addition of corn residues in the absence of plants was assessed. The abundance of hyphae was higher in the presence of the mycorrhizal plants than in the other treatments. AM hyphae present under mycorrhizal plants accounted for more than 83% of the measured hyphae. The levels of root colonization of 32% in corn and 27% in barley confirmed the mycorrhizal status of the experimental plants. Only a few points of entry were observed in canola, the non-host plant. The percentage of mycorrhizal colonization was positively related (R ²?=?0.85) to the abundance of soil hyphae, indicating that AM hyphae were the major component of the soil hyphae in the presence of mycorrhizal plants in this study.     

接种AMF对菌根植物和非菌根植物竞争的影响

为了研究丛枝菌根真菌(arbuscular mycorrhizal fungus, AMF)对菌根植物与非菌根植物种间竞争的影响,以玉米(菌根植物)和油菜(非菌根植物)作为供试植物,分别进行间作、尼龙网分隔和单作,模拟这两种植物之间不同的竞争状态,接种丛枝菌根真菌Glomus intraradices和Glomus mosseae,比较菌根植物和非菌根植物的生长和磷营养状况,分析AMF侵染对植物种间竞争作用的影响。结果显示,与单作相比,间作模式下玉米的生物量及磷营养状况有所降低,但其菌根依赖性却有所提高。与不接种相比,接种处理显著降低了间作体系油菜根系的磷含量和磷吸收量,但趋于改善菌根植物玉米的磷营养状况。因此,接种AMF可以降低非菌根植物的磷营养状况及生物量,使得菌根植物的相对竞争能力明显提高,说明AMF在维持物种多样性方面有着重要的作用。     

Physiological Significance of Network Organization in Fungi

The evolution of multicellularity has occurred in diverse lineages and in multiple ways among eukaryotic species. For plants and fungi, multicellular forms are derived from ancestors that failed to separate following cell division, thus retaining cytoplasmic continuity between the daughter cells. In networked organisms, such as filamentous fungi, cytoplasmic continuity facilitates the long-distance transport of resources without the elaboration of a separate vascular system. Nutrient translocation in fungi is essential for nutrient cycling in ecosystems, mycorrhizal symbioses, virulence, and substrate utilization. It has been proposed that an interconnected mycelial network influences resource translocation, but the theory has not been empirically tested. Here we show, by using mutants that disrupt network formation in Neurospora crassa (Δso mutant, no fusion; ΔPrm-1 mutant, ∼50% fusion), that the translocation of labeled nutrients is adversely affected in homogeneous environments and is even more severely impacted in heterogeneous environments. We also show that the ability to share resources and genetic exchange between colonies (via hyphal fusion) is very limited in mature colonies, in contrast to in young colonies and germlings that readily share nutrients and genetic resources. The differences in genetic/resource sharing between young and mature colonies were associated with variations in colony architecture (hyphal differentiation/diameters, branching patterns, and angles). Thus, the ability to share resources and genetic material between colonies is developmentally regulated and is a function of the age of a colony. This study highlights the necessity of hyphal fusion for efficient nutrient translocation within an N. crassa colony but also shows that established N. crassa colonies do not share resources in a significant manner.     

Pitcher plant facilitates prey capture in a sympatric congener

Carnivorous plants avoid below-ground competition for nitrogen by utilizing an alternative nitrogen resource—invertebrate prey, but it remains unclear if sympatric carnivorous plants compete for prey resources. The aim of this study was to investigate if exploitative prey-resource competition occurs between the two sympatric pitcher plant species, Nepenthes rafflesiana and N. gracilis in Singapore. We first investigated if prey-resource partitioning occurs between these two species, and then investigated niche shift in N. gracilis by examining its pitcher contents along an in situ gradient of N. rafflesiana interspecific competition. Our results showed clear evidence of resource partitioning between the two species, but contrary to the expectation of competition, proximity to N. rafflesiana pitchers correlated with higher total prey numbers in N. gracilis pitchers. Our multivariate model of prey assemblages further suggested that N. rafflesiana facilitates N. gracilis prey capture, especially in several ant taxa that are trapped by both species. Concurrently, we found strong evidence for intraspecific competition between N. gracilis pitchers, suggesting that prey resources are exhaustible by pitcher-predation. Our results show that resource partitioning can be associated with facilitative interactions, instead of competition as is usually assumed. Facilitation is more typically expected between phylogenetically distant species, but divergences in resource acquisition strategies can permit facilitation between congeners.     

Clonal plant <Emphasis Type="Italic">Duchesnea indica</Emphasis> Focke forms an effective survival strategy in different degrees of Pb-contaminated environments

Clonal plants in heterogeneous environments can benefit from habitat selection, giving them the ability to utilize patchily distributed resources efficiently. However, most research is conducted in a resource heterogeneous environment, and the study of heterogeneous environment of non-resource material (copper, cadmium, lead, and so on) is limited. Research into clonal plant growth under heterogeneous toxic conditions could contribute to our understanding of the strategy of the selective establishment pattern. Thus, we examined clonal growth in a heterogeneous lead environment to enhance understanding of habitat selection strategies. The growth indices (stolon-length, ramet number, biomass, and lead-concentrations) of Duchesnea indica were examined under three levels (low, moderate, and high were represented by 0, 50 and 100%) of lead contamination and two degrees of heterogeneity (low and high heterogeneity under moderate contamination) environments in a glasshouse study. Habitat selection strategy was analyzed by clone growth pattern, labor division, and risk-spreading. The clones under the moderate contamination level, especially with high heterogeneity, demonstrated the optimal growth. They expanded their growth-pattern to escape the toxic environment, and rooted more ramets in the unpolluted patches, allocating more aboveground biomass to these areas. Moreover, parent ramets transported their lead in the soil to the offspring. The offspring spread the toxic risk by accumulating lead in their roots and producing more ramets. Optimal growth of clonal plants occurred in environments moderately contaminated with lead, especially under higher heterogeneity, which performed effective survival strategy by expensive growth architecture, aboveground biomass increase and risk-spreading.     

How belowground interactions contribute to the coexistence of mycorrhizal and non-mycorrhizal species in severely phosphorus-impoverished hyperdiverse ecosystems

Background

Mycorrhizal strategies are very effective in enhancing plant acquisition of poorly-mobile nutrients, particularly phosphorus (P) from infertile soil. However, on very old and severely P-impoverished soils, a carboxylate-releasing and P-mobilising cluster-root strategy is more effective at acquiring this growth-limiting resource. Carboxylates are released during a period of only a few days from ephemeral cluster roots. Despite the cluster-root strategy being superior for P acquisition in such environments, these species coexist with a wide range of mycorrhizal species, raising questions about the mechanisms contributing to their coexistence.

Scope

We surmise that the coexistence of mycorrhizal and non-mycorrhizal strategies is primarily accounted for by a combination of belowground mechanisms, namely (i) facilitation of P acquisition by mycorrhizal plants from neighbouring cluster-rooted plants, and (ii) interactions between roots, pathogens and mycorrhizal fungi, which enhance the plants’ defence against pathogens. Facilitation of nutrient acquisition by cluster-rooted plants involves carboxylate exudation, making more P available for both themselves and their mycorrhizal neighbours. Belowground nutrient exchanges between carboxylate-exuding plants and mycorrhizal N₂-fixing plants appear likely, but require further experimental testing to determine their nutritional and ecological relevance. Anatomical studies of roots of cluster-rooted Proteaceae species show that they do not form a complete suberised exodermis.

Conclusions

The absence of an exodermis may well be important to rapidly release carboxylates, but likely lowers root structural defences against pathogens, particularly oomycetes. Conversely, roots of mycorrhizal plants may not be as effective at acquiring P when P availability is very low, but they are better defended against pathogens, and this superior defence likely involves mycorrhizal fungi. Taken together, we are beginning to understand how an exceptionally large number of plant species and P-acquisition strategies coexist on the most severely P-impoverished soils.

     

接种AM真菌对玉米和油菜种间竞争及土壤无机磷组分的影响

在温室盆栽条件下,分别模拟单作、间作和尼龙网分隔种植,比较接种丛枝菌根(arbuscular mycorrhizal, AM)真菌Glomus intraradices和Glomus mosseae对菌根植物玉米和非菌根植物油菜生长和磷吸收状况的影响,并分析土壤中各无机磷组分的变化。结果发现,接种AM真菌可以促进土壤中难溶性磷(Ca₁₀-P和O-P)向有效态磷转化,并显著降低总无机磷含量 (P<0.05),显著提高菌根植物玉米的生物量和磷吸收量(P<0.05),特别是在间作体系中使玉米的磷营养竞争比率显著提高了45.0%-104.1% (P<0.05),显著降低了油菜的生物量和磷吸收量(P<0.05),从而增强了了菌根植物的竞争优势,降低了非菌根植物与菌根植物的共存能力。揭示了石灰性土壤中AM真菌对植物物种多样性的影响,有助于更加全面地理解AM真菌在农业生态系统中的作用。     

Arbuscular mycorrhizal fungi reduce effects of physiological integration in Trifolium repens

Background and Aims

One of the special properties of clonal plants is the capacity for physiological integration, which can increase plant performance through mechanisms such as resource sharing and co-ordinated phenotypic plasticity when plants grow in microsites with contrasting resource availabilities. However, many clonal plants are colonized by arbuscular mycorrhizal fungi (AMF). Since AMF are likely to reduce contrasts in effective resource levels, they could also reduce these effects of clonal integration on plasticity and performance in heterogeneous environments.

Methods

To test this hypothesis, pairs of connected and disconnected ramets of the stoloniferous herb Trifolium repens were grown. One ramet in a pair was given high light and low nutrients while the other ramet was given high nutrients and low light. The pairs were inoculated with zero, one or five species of AMF.

Key Results

Pairs of ramets grown without AMF developed division of labour and benefited from resource sharing, as indicated by effects of connection on allocation to roots, accumulation of mass, and ramet production. Inoculation with five species of AMF significantly reduced these effects of connection, both by inhibiting them in ramets given high nutrients and inducing them in ramets given high light. Inoculation with one species of AMF also reduced some effects of connection, but generally to a lesser degree.

Conclusions

The results show that AMF can significantly modify the effects of clonal integration on the plasticity and performance of clonal plants in heterogeneous environments. In particular, AMF may partly replace the effects and benefits of clonal integration in low-nutrient habitats, possibly more so where species richness of AMF is high. This provides the first test of interaction between colonization by AMF and physiological integration in a clonal plant, and a new example of how biotic and abiotic factors could interact to determine the ecological importance of clonal growth.Key words: Arbuscular mycorrhizal fungi, biomass allocation, clonal plant, division of labour, environmental heterogeneity, light availability, nutrients, white clover     

The co-existence between DSE and AMF symbionts affects plant P pools through P mineralization and solubilization processes

The capacity of dark septate endophytes (DSE; Phialocephala turiciensis, Acephala applanata, P. glacialis and Phaeomollisia piceae) to solubilize inorganic phosphate (P) and to mineralize the organic form was studied. We analysed the effect of DSE strains on P uptake by Trifolium repens in the presence or absence of arbuscular mycorrhizal fungi (AMF). Phosphatases were observed both in the absence of the host plant and the organic resource, showing that the P mineralization process is not induced by the enzyme substrate or the host. DSE were more efficient at mineralizing organic P. Independently of the presence of AMF, DSE increased the pool of P in the soil, with significant differences being found in P levels among the different DSE. In contrast, plant P uptake was increased by AMF. The P content of plants increased with the co-inoculation of AMF and P. turiciensis or P. piceae. We hypothesize a close relationship between DSE and AMF in relation to P availability and uptake in plants. Whereas DSE increase the pool of P in the rhizosphere, AMF are responsible for P transfer to the host, with co-colonization of plants by DSE and AMF showing a synergistic outcome.     

Quantifying dynamic resource allocation illuminates foraging strategy in Phanerochaete velutina

Saprotrophic woodland fungi forage for mineral nutrients and woody resources by extension of a mycelial network across the forest floor. Different species explore at different rates and establish networks with qualitatively differing architecture. However, detailed understanding of fungal foraging behaviour has been hampered by the absence of tools to quantify resource allocation and growth accurately and non-invasively. To solve this problem, we have used photon-counting scintillation imaging (PCSI) to map and quantify nutrient allocation and localised growth simultaneously in heterogeneous resource environments. We show that colonies spontaneously shift to an asymmetric growth pattern, even in the absence of added resources, often with a distinct transition between the two growth phases. However, the extent of polarisation was much more pronounced and focussed in the presence of an additional cellulose resource. In this case, there was highly localised growth, often at the expense of growth elsewhere in the colony, and marked accumulation of ¹⁴C-AIB in the sector of the colony with the added resource. The magnitude of the response was greatest when resource was added around the time of the endogenous developmental transition. The focussed response required a metabolisable resource, as only limited changes were seen with glass fibre discs used to mimic the osmotic and thigmotropic stimuli upon resource addition. Overall the behaviour is consistent with an adaptive foraging strategy, both to exploit new resources and also to redirect subsequent foraging effort to this region, presumably with an expectation that the probability of finding additional resources is increased.     

Different arbuscular mycorrhizal interactions in male and female plants of wild Carica papaya L.

The different resource demands on male and female plants of dioecious species can lead to secondary sexual dimorphisms. Male and female plants might also interact differently with antagonists and mutualists. We used a repeated measures natural experiment in five subpopulations to investigate secondary sexual dimorphism in Carica papaya including interactions with arbuscular mycorrhizal fungi. Male and female plants did not differ in size or growth rate, but male plants flowered earlier than female plants. We observed different patterns of root colonization by arbuscular mycorrhizal fungi in male and female plants of C. papaya. These differences between the sexes preceded the flowering of most female plants. Female plants were sensitive to changes in soil fertility and adjusted the extent of their root colonization by arbuscular mycorrhizal fungi accordingly. Overall, the different resource demands on male and female plants seem to modulate the interactions of C. papaya with arbuscular mycorrhizal fungi.     

The Impact of Resource Availability on Bacterial Resistance to Phages in Soil

Resource availability can affect the coevolutionary dynamics between host and parasites, shaping communities and hence ecosystem function. A key finding from theoretical and in vitro studies is that host resistance evolves to greater levels with increased resources, but the relevance to natural communities is less clear. We took two complementary approaches to investigate the effect of resource availability on the evolution of bacterial resistance to phages in soil. First, we measured the resistance and infectivity of natural communities of soil bacteria and phage in the presence and absence of nutrient-providing plants. Second, we followed the real-time coevolution between defined bacteria and phage populations with resource availability manipulated by the addition or not of an artificial plant root exudate. Increased resource availability resulted in increases in bacterial resistance to phages, but without a concomitant increase in phage infectivity. These results suggest that phages may have a reduced impact on the control of bacterial densities and community composition in stable, high resource environments.     

Modularity Reveals the Tendency of Arbuscular Mycorrhizal Fungi To Interact Differently with Generalist and Specialist Plant Species in Gypsum Soils

Patterns in plant–soil biota interactions could be influenced by the spatial distribution of species due to soil conditions or by the functional traits of species. Gypsum environments usually constitute a mosaic of heterogeneous soils where gypsum and nongypsum soils are imbricated at a local scale. A case study of the interactions of plants with arbuscular mycorrhizal fungi (AMF) in gypsum environments can be illustrative of patterns in biotic interactions. We hypothesized that (i) soil characteristics might affect the AMF community and (ii) there are differences between the AMF communities (modules) associated with plants exclusive to gypsum soils (gypsophytes) and those associated with plants that show facultative behavior on gypsum and/or marly-limestone soils (gypsovags). We used indicator species and network analyses to test for differences between the AMF communities harbored in gypsophyte and gypsovag plants. We recorded 46 operational taxonomic units (OTUs) belonging to nine genera of Glomeromycota. The indicator species analysis showed two OTUs preferentially associating with gypsum soils and three OTUs preferentially associating with marly-limestone soils. Modularity analysis revealed that soil type can be a major factor shaping AMF communities, and some AMF groups showed a tendency to interact differently with plants that had distinct ecological strategies (gypsophytes and gypsovags). Characterization of ecological networks can be a valuable tool for ascertaining the potential influence of above- and below-ground biotic interactions (plant-AMF) on plant community composition.     

Bioenergetic theory predicts infection dynamics of human schistosomes in intermediate host snails across ecological gradients

Epidemiological dynamics depend on the traits of hosts and parasites, but hosts and parasites are heterogeneous entities that exist in dynamic environments. Resource availability is a particularly dynamic and potent environmental driver of within‐host infection dynamics (temporal patterns of growth, reproduction, parasite production and survival). We developed, parameterised and validated a model for resource‐explicit infection dynamics by incorporating a parasitism module into dynamic energy budget theory. The model mechanistically explained the dynamic multivariate responses of the human parasite Schistosoma mansoni and its intermediate host snail to variation in resources and host density. At the population level, feedbacks mediated by resource competition could create a unimodal relationship between snail density and human risk of exposure to schistosomes. Consequently, weak snail control could backfire if reductions in snail density release remaining hosts from resource competition. If resource competition is strong and relevant to schistosome production in nature, it could inform control strategies.     

土著菌根真菌和混生植物对羊草生长和磷营养的影响

植物种间相互作用直接影响植物生长、根系可塑性及养分吸收,而与植物共生的丛枝菌根真菌可以改变植物个体和种间养分资源的分配,具有协调种间竞争的潜力.以我国北方草甸草原建群种羊草(Leymus chinensis)和混生植物紫花苜蓿(Medicago sativa)及独行菜(Lepidium spetalum)为供试植物,通过模拟盆栽试验,研究了土著菌根真菌和混生植物对羊草生长、根系形态及磷营养的影响.试验结果表明,土著菌根真菌能够与羊草及紫花苜蓿形成良好共生,而独行菜根内基本未形成菌根共生结构.土著菌根真菌显著降低了羊草及独行菜的生物量,但促进了紫花苜蓿的生长;混种紫花苜蓿显著促进了羊草的生长,而混种独行菜则显著抑制了羊草的生长.土著菌根真菌对羊草根系形态的影响表现出与植株生物量类似的趋势,但不同混生植物对羊草根系生长均无显著影响.土著菌根真菌和混生植物对羊草植株磷含量均无显著影响.与混生植物相比,羊草具有较高的比根长和磷吸收能力,这也解释了其负向菌根依赖性.研究证实了菌根真菌和植物种间相互作用均是影响草原优势植物生长和根系发育的重要因素,深入研究其交互作用对于科学管理草地生态系统,维持植物群落的稳定性和生态系统生产力具有重要意义.