Mycorrhizal fungi
Aims Arbuscular mycorrhizal (AM) symbiosis plays an important role in plant adaptation to phosphorus (P) deficiency. The mycorrhizal fungi can directly regulate P stress response of the host plants, and can also indirectly influence neighbor plants via AM exudates. This study aimed to reveal the regulation mechanisms of plant response to P deficiency by AM associations. Methods In a compartmentation cultivation experiment with Zea mays ‘B73’ and AM fungus Rhizophagus irregularis ‘DAOM197198’, we investigated mycorrhizal effects on plant P nutrition and the expression of plant and fungal genes related to P and carbon (C) metabolisms under both low P (10 mg?kg-1) and high P (100 mg?kg-1) conditions. The cultivation system consisted of three compartments, namely donor compartment, buffer compartment and receiver compartment divided by two pieces of microporous filters with pore size of 0.45 μm. Maize plant in donor compartment inoculated with AM fungus served as a source of AM exudates. The microporous filters could restrict the development of extraradical mycelium of AM fungi, but allow diffusion of AM exudates. Real-time PCR was performed to quantify the gene expression levels both in maize plants and AM fungi. Important findings The experimental results indicated that under low P conditions mycorrhizal colonization increased plant dry weight and P concentration in donor plants, and up-regulated plant genes encoding P transporters Pht1;2, Pht1;6, phosphoenolpiruvate carboxylase (PEPC), inorganic pyrophosphatase (TC289), glycerol-3-phosphate transporter (G3PT) and malate synthase (MAS1). The expression of AM fungal genes encoding P transporter (GiPT), GlcNAc transporter (NGT1), GlcNAc kinase (HXK1b), GlcNAc phosphomutase (AGM1), UDP GlcNAc pyrophosphorylase (UAP1), chitin synthase (CHS1), GlcNAc-6-phosphate deacetylase (DAC1) and glucosamine-6-phosphate isomerase (NAG1) was significantly higher under low P conditions compared with high P conditions. However, for the receiver plants, plant dry mass and P concentration were only significantly increased by higher P addition, while inoculation treatment significantly up-regulated the expression of P transporter genes Pht1;2 and Pht1;6, C metabolism related genes G3PT, PEPC, TC289 and MAS1. The study proved that AM exudates could potentially stimulate plant response to P deficiency by regulating functional genes relevant to P and C metabolisms in the mycorrhizal associations.
Aims To understand the ecological significance of arbuscular mycorrhizal (AM) fungi associated with Hedysarum scoparium in semi-arid and arid lands, species diversity and ecological distribution of AM fungi associated with Hedysarum scoparium were elucidated in a desert ecosystem of northwestern China.
Methods Soil samples (0–30 cm depth) under Hedysarum scopariumis were collected at seven different sites (Ordos, Wuhai, Dengkou, Alxa, Shapotou, Minqin, Anxi) in northwest China in July 2015. Based on the morphological characteristics of spores, AM fungi were identified, and redundancy analysis (RDA) was used to distinguish among different groups. Furthermore, the relationship between species diversity of AM fungi and soil factors were evaluated by Pearson’s correlation analysis.
Important findings A total of 42 AM fungal species belonging to six genera were isolated. Among these, 16 species belong to Glomus,17 to Acaulospora four to Claroideoglomus,two to Septoglomus,two to Funneliformis and one to Scutellospora.The abundance, spore density and Shannon-Wiener index of AM fungi decreased gradually along the aridity gradient from east to west. Spore density of AM fungi of different species in the same site were different, and those of the same species in different sites were also different. Soil organic matter, pH,ammonia, and available phosphorus had significant effects on AM fungi. The results showed that the species diversity and distribution of AM fungi have obvious spatial patterns, and were influenced by soil factors, among which soil moisture was the most significant factor.
Aims Soil respiration component partitioning is pivotal to understand the belowground carbon (C) cycle. Mycorrhizal fungi have been proven to play an important role in the soil C turnover, but only a few studies have been conducted to quantify the contribution of mycorrhizal respiration to total soil respiration in grassland ecosystems.Methods The mini-trenching mesh method was applied to partition soil respiration components of a semi-arid grassland in Inner Mongolia. A shallow collar (measuring soil total respiration), a deep collar (excluding roots and mycorrhizal hypahe) and a deep collar with 40 μm pore mesh window (excluding roots but not mycorrhizal hyphae) were installed in each plot. Soil respiration rate of each collar was measured every two weeks during the growing season from 2014 to 2016. The differences in the rate of soil respiration among different type of collars were used to partition the components of soil respiration.Important findings The results showed that the contribution of heterotrophic, root and mycorrhizal respiration to total soil respiration was 49%, 28%, and 23%, respectively. Across the three years, the proportion of mycorrhizal respiration varied from 21%-26%, which is comparable with the results reported by other studies recently. Our results demonstrated that the mini-trenching mesh method is a suitable method for separating mycorrhizal respiration component in grassland ecosystems. Evaluating the contribution of mycorrhizal respiration to total soil respiration is very important for predicting the responses of soil carbon release to future climate change.
Aims Arbuscular mycorrhizal fungi (AMF) can form symbiotic associations with most terrestrial plants to improve plant growth and stress resistance. It has been well demonstrated that AMF can promote plant acquisition of water and enhance plant tolerance to drought. In this study, AMF extraradical hyphae were obtained from in vitro culture of AMF Rhirophagus irregularis with hairy carrot (Daucus carota var. sativa) root to investigate the morphological and physiological changes of hyphae in response to drought stress induced by polyethylene glycol (PEG).
Methods The influence of drought stress on the hyphal morphology was observed by using the field emission-scanning electron microscope-energy dispersive X-ray spectroscopy (FE-SEM-EDS), while H + and Ca 2+ion fluxes through living hyphae were monitored by non-invasive micro-test technique (NMT).
Important findings The results showed that significant H+ efflux and Ca2+ influx through the tip and side of the extraradical hyphae were detected in response to drought stress induced by PEG for 1 h. Fluorescence probing confirmed that the intracellular pH value and Ca2+ concentration of hyphae significantly increased under PEG treatment. The morphology of hyphae changed and the pH value of the growth medium decreased after treatment with PEG for 24 h. The P, Ca, and Fe elements accumulated at the hyphosphere to enhance the nutrient absorption by hyphae. The study confirmed that AMF regulated the transmembrane H+ and Ca2+ flux to promote the material exchange between hyphae and environment under drought stress. The acidification of the hyphosphere environment potentially promoted the absorption of nutrients and also the signal exchange between AMF and the host plant to enhance plant drought tolerance.
Invasive alien plants not only influence plant community composition, biodiversity and ecosystem structure and function, but also have severe impacts on soil nitrogen transformation processes. The effects of invasive alien plants on nitrogen (N) cycling have been one of the hot topics in invasion ecology. Litter decomposition and its nutrient release play an important role in nutrient cycling. In addition, invasive alien plants have the potential to influence soil N transformation through allelopathy. All these processes are tightly related to soil microbes. Therefore, this review mainly focuses on litter decomposition and its nutrient release, and allelopathy to understand the effects of plant invasion on soil N transformation. Changes in soil N transformation and soil microbes (esp. Ammonia oxidizing bacteria and Ammonia oxidizing archaea) due to plant invasion, as well as the feedbacks of these changes to further invasion of alien plants were discussed. Finally, the interactions between arbuscular mycorrhizal fungi and plant invasion were reviewed.
Aims Accumulating evidence suggests that arbuscular mycorrhizal fungi (AMF) can promote the growth of plant roots. However, the effects of AMF on the root growth of dioecious plants, particularly those grown under different sexual combination patterns, remain largely unknown, this study therefore aimed at improving our understanding of the roles of AMF in these systems.Methods In the present study, homogenized soil (river sand:surface soil:vermiculite = 1:1:1, volume ratio) was used as growth substrate. The Populus cathayana saplings uninoculated and inoculated with AMF under three sex combination patterns (male vs. male, MM; female vs. female, FF; male vs. female, MF) were defined as control (CK) and AMF treatment group, respectively. Subsequently, we compared the differences in colonization rate, root dry mass, root morphology, carbon (C) content and nitrogen (N) content between CK and AMF treatments under different sexual combination patterns.Important findings Our results indicated that colonization rate, root dry mass, root morphology (except root branching intensity, specific root surface area) and C, N content were remarkably altered upon inoculation with AMF in comparison to uninoculated controls. Furthermore, the sexual combination patterns were shown to significantly affect root dry mass, root morphology and C, N content of male and female P. cathayana. After inoculation with AMF, root dry mass, root morphology and N content of female individuals were increased whereas these parameters of males were decreased or slightly increased in inter-sexual groups compared with the respective intra-sexual groups. Collectively, our data demonstrate the growth-promoting effects of AMF on the roots of P. cathayana individuals grown under different sexual combination patterns, and such beneficial effects are most pronounced in females grown under inter-sexual combination patterns.
AimsPrevious studies have shown that Dendrobium plants form a specific symbiotic relationship with fungi at differentiation stages during natural seed germination. In order to explore the evolution and adaptation of this symbiotic relationship in interspecific hybrid progenies, this study was to understand whether the strong specificity with symbiotic fungi during seedling formation and differentiation was also an important factor limiting the formation of hybrid progenies in Dendrobium, and the relationship between hybrid progenies of orchids and symbiotic fungi during seed germination stage.MethodsThe effects of fungi on germination of interspecific hybrid seeds of D. officinale and D. tortile were studied using the highly specific fungi strains Tulasnella SSCDO-5 and Epulorhiza FDd1, which can effectively promote seed germination and seedling formation in D. officinale and D. devonianum, respectively.Important findings The results showed that both SSCDO-5 and FDd1 strains could effectively promote the protocorm and seedling formation of hybrid seeds after 68 days incubation with no significant difference. The SSCDO-5 strain from D. officinale did not show any advantages, and the seedling formation rate of hybrid was lower than that of FDd1 strain from D. devonianum. The seedling formation rate incubation with SSCDO-5 strain was (22.13 ± 6.62)% while with FDd1 strain was (29.53 ± 5.51)%. The specificity of SSCDO-5 strain with D. officinale at seedling formation and development stage was not inherited or expressed in hybrid progenies, indicating that hybridization broke the symbiotic relationship of this specificity, which enabled hybrid progenies to establish new symbiotic relationship with different fungi. Our results do not support the hypothesis that the specificity of symbiotic fungi is an important limiting factor for the formation of hybrid progenies in Dendrobium. We speculate that the symbiotic relationship between Dendrobium plants and fungi during seedling differentiation and development is formed and established in the process of adapting to specific ecological environment.
Nitrogen (N) deposition has profound impacts on the phosphorus (P) cycling in forest ecosystems. Especially, the aggravated P limitation on tree growth under N addition has caused much attention to researchers. This article reviews the effects of N addition on plant P content in forest ecosystems. The result showed that N addition increased soil available P and facilitated the absorption of P by plants by promoting soil phosphatase activity, thereby increasing plant P content. Furthermore, changes in tree P content following N addition were also affected by species, life forms as well as experimental duration. Due to the inconsistency, the underlying mechanisms of changes in P content under N addition were further summarized as follows: 1) changes in soil available P content induced by exogenous N input affected the source of plant P; 2) N input affected the P uptake capacity of plants by affecting plant root exudates, mycorrhizal symbiosis and root morphological structure; 3) plant P utilization efficiency was also influenced with changes of P re-distribution and P re-absorption. Overall, for the changes in plant P under increasing exogenous N inputs, alterations of soil available P under N addition was the primary factor, while changes in plant P uptake capacity and P utilization efficiency ulteriorly regulated plant P content.
Aims Null model is an important basis for nesting judgment. Highly asymmetric structures often appear in plant symbolic fungal networks. This study aims to explore the influence of matrix asymmetric changes on network nesting judgment.Methods The study was conducted based on various null model construction methods.Important findings Constraints vary with changing null models, with reducing null space when additional qualifications were added during null model establishment. Highly constrained nulls are prone to causing type II errors. Highly asymmetric networks increase matrix temperature (NT) deviation based on random (Equiprobable- equiprobable, r00) null model while reducing overlap and decreasing fill (NODF) deviation. Values of z-score show that highly asymmetric networks contribute to the significant determination level of NT and NODF. The impacts on the judgment of nestedness of asymmetric networks differ between row and column fixed null models. The effects of network asymmetry change on nesting detection based on column constrained (c0) nulls are similar to that of random null model, but with smaller nesting deviation and standard deviations. No significant differences in both NT and NT deviations were observed among different asymmetry networks based on the row fixed (r0) nulls, with a lower NODF deviation in highly asymmetric network based on c0 nulls. To more accurately determine whether the asymmetric networks would have nested structures, we recommend using a combination of random and constrained null models. Our results also demonstrate that the r0 null model performs better than either the r00 null model or the c0 null model when comparing nesting level of different asymmetric networks.
Aims Orchid plants generally grow better when they are mycorrhizal since mycorrhizal fungi are likely to assist in orchid seeds’ germination. However, there is little quantitative work on it. Thus we hope to better understand this mechanism to benefit the orchid plants protection. Methods We studied nine small population species of orchids grown in Liaoning Province, China. We analyzed the composition of orchid mycorrhizal fungi (OMF) and fungal communities in the roots, in the rhizosphere soil as well as bulk soil, by taking advantage of the next generation sequencing technology. Important findings Our study showed that there was a significant difference in fungal communities among in the roots, the rhizosphere soil and the bulk soil, especially in the total operational taxonomic unit (OTU) number. Although the OTU number was far smaller in the roots than in the rhizosphere soil and bulk soil, the species and abundances of OMF were less relative to each other. FunGuild, an indicator to predict the functional fungi, indicated that Arbuscular Mycorrhizal fungi were abundence in the rhizosphere while were rare in the roots of orchids. In general, the fungal communities in the roots were not tightly correlated with that in the root-associated soil.
Aims Arbuscular mycorrhizal fungi (AMF) form symbiotic relationships with most terrestrial plants, contributing to the nutrient uptake of host plants. While little is known on how rhizospheric microorganisms affect the relationships between AMF and host plants under nutritional stress. We hypothesize that AMF may compete for nutrients with host plants in extremely nutrient-limited environments, such as nitrogen deficient habitats, and nitrogen-fixing bacteria will alleviate the competition.Methods In order to test our hypotheses, we grew Solidago canadensis plants under nitrogen deficient treatments. We inoculated plants with AMF and a nitrogen-fixing bacterium to test the relationships among the host plant and microorganisms.Important findings Under the lowest nitrogen level (0.025 mmol·L-1 N of ammonium nitrogen), the growth of S. canadensis was more restricted with AMF colonization, suggesting competition between AMF and the host. However, with the inoculation of nitrogen-fixing bacterium, AMF colonization was promoted and plant growth was increased. These results indicate that nitrogen-fixing bacteria could moderate the competition for nutrients between AMF and their host under nitrogen deficiency. This study improves our understanding of the invasion mechanisms of alien plants, where they interact with different microorganisms under extreme nutrient stress.
Mycorrhizal fungi symbiosis is an important strategy for plant to uptake soil nutrients. Alien plants could thwart the symbiotic relationship between native plants and mycorrhizal fungus, and thus suppress the growth of native plants, which is an important mechanism for alien plant invasion, and has been increasingly emphasized in recent studies. In the present review, we summarized several key aspects of such mycorrhizal-related mechanism of plant invasion: 1) the impacts of alien plants on mycorrhizal fungi of native plants (i.e. mycorrhizal colonization rate, internal structures of mycorrhizal hyphae, amount of external hyphae, mycorrhizal and non-mycorrhizal composition, and mycorrhizal network); 2) mechanisms of alien-plant impacts on mycorrhizal fungi of native plants, including ecological mechanisms such as resource competition, allelopathy and edaphic fertility, as well as their molecular mechanisms; 3) variations of the above mentioned alien-plant impacts and related mechanisms at different durations of plant invasion. Despite thwarting mycorrhizal fungi of native plants is an important mechanism for alien plant invasion, researches on such mechanism are still scarce comparing to other mechanisms such as natural enemy release and new weapon hypothesis. Therefore, we proposal several research areas that need to be focused on in future studies: 1) how do global changes affect the alien-plant-invasion impacts on mycorrhizal fungi of native plants; 2) what are the relationships among different mechanisms including the mycorrhizal-related mechanism; 3) how does the mycorrhizae-related mechanism change at large spatio-temporal scales.
Aims Plants absorb mineral nutrients such as nitrogen (N) mainly through their roots. The nutrient uptake of plants with different root morphologies differs. Many studies have shown that arbuscular mycorrhizal fungi (AMF) can help their symbiotic associates absorb mineral N. However, there is little research on whether the effect of AMF on nutrient uptake of plant roots is affected by root morphology.
Methods In this study, we selected three rice mutants and one wild type (root hairless (rhl1), lateral rootless (iaa11), adventitious rootless (arl1) and wild type (Kas)) to investigate the role of root morphology in plant nutrient uptake. Subsequently, we used the 15N isotope labeling method to explore the effects of arbuscular mycorrhizal fungi and N addition (low N: 20 mg·kg-1 NH4+-N; high N: 100 mg·kg-1 NH4+-N) on N uptake of rice mutants with different root morphologies.
Important findings The results show that the leaf 15N concentrations of rhl1,Kas, iaa11 and arl1 were increased by 60%, 72%, 128% and 118%, respectively, under the high N compared to the low N treatment. This result indicates that the addition of N significantly promoted rice N uptake with the most evident effect occurring in iaa11 and arl1. The average effect sizes of AMF on rhl1, Kas, iaa11 and arl1 were 17%, 31%, 42% and 51% under the low N level, indicating that root morphology can alter the effect of AMF on plant N uptake. Compared to the low N treatment, high N significantly downregulated the AMF effect on N uptake by rice plants with different root morphologies, indicating that N addition may mediate the complementary effect of AMF and root morphology on plant nutrient uptake. In conclusion, our data provide direct experimental evidence of funcitonal complementarity of mycrrohzal fungi and their associated roots with different root morphogy.
Aims The increasing deposition of nitrogen (N) has led to an imbalance of N and phosphorus (P) in forest soils, and has become the focus of ecological studies. Fungi, as one of the main microorganisms in soils, plays an important role in maintaining nutrient balance and promoting plant growth. Enhancing the understanding of the growth status of Cunninghamia lanceolata seedlings and the changes of soil fungal community structure and functional groups under the treatments of N addition, are helpful to study the process of soil nutrient cycling, and provide references for scientific management and sustainable development of C. lanceolata plantation.
Methods In this study, we used high-throughput sequencing and FUNGuild functional prediction to determine changes in soil fungal structural composition and functional groups of C. lanceolatain response to the application of control (0 kg N·hm-2·a-1), low N (40 kg N·hm-2·a-1), and high N (80 kg·N hm-2·a-1) treatments.
Important findings The results showed that N addition reduced biomass and leaf P content of C. lanceolata seedlings. Ascomycota, Basidiomycota, and Mortierellomycota were the three dominant phyla in the experimental soils, and accounted for 76.71%-86.72% of the relative abundance among the entire fungal community. The effect of short-term N addition on fungal composition was not significant at the phylum level. However, the relative abundance of Glomeromycota increased significantly with the low N treatment. At the order level, compared with the control, low N treatment significantly increased the relative abundance of Mortierellales. High N treatment significantly increased the relative abundance of Tremellales, but significantly reduced that of Sordariales. In addition, low N treatment significantly increased soil available P content, and there were significant positive correlations with the relative abundances of Glomeromycota and Mortierellales. These results indicate that N addition may maintain P availability of C. lanceolatagrowth by altering the fungi associated with P transformation. In addition, the relative abundance of saprotroph group was significantly reduced under low N treatment, but the relative abundance of arbuscular mycorrhizal fungi was significantly increased. In conclusion, soil fungal functional groups can participate in soil nutrient cycling by changing the relative abundance of different functional groups.
Changes in soil nutrient availability and primary succession of vegetation often co-occur during the processes of natural soil development. A low availability of nitrogen (N) and phosphorus (P) resources is common in the very early and late stage of soil development, respectively. Plants have evolved different nutrient-acquisition strategies (NASs) in response to low nutrient availability. Although the changes and responses of plant NASs to soil nutrients may affect primary succession and species diversity, the temporal trends and underlying mechanisms of plant NASs with soil development remain unknown. We reviewed 104 studies mainly carried out on soil chronosequences to clarify changes in plant NASs with soil age and its ecological significance. We classify plant NASs into Fine root, Microbial, Specialized root, Carnivorous and Parasitic strategies. We argue that the diversity of plant NASs changes with increasing soil age following a dumbbell-pattern, while reaching the maximum in the late stage of soil development. The role of Microbial and Fine root strategies in plants acquiring nutrients gradually decreases with increasing soil age, while the minimum and maximum role of Specialized root strategies in plants acquiring P is in the intermediate and late stages of soil development, respectively. The effects of NASs on interspecific relationships of plants vary with soil age. Specifically, pioneer plants with biological N fixation and specialized root strategies usually increase available soil N and regolith-derived nutrients to facilitate the colonization of subsequent plants in the early stage of soil development. During the early-intermediate stage, NASs mainly affect plant competitiveness in acquiring relatively abundantly available nutrients from soil. The facilitation and competition affected by NASs contribute to plant species turnover in the first two stages. In the late stage, diverse NASs enable plants to acquire distinct forms of nutrients from different soil spaces and complementary NASs enable plants to take up soil nutrients mobilized by their neighbors. Together with the interactions between NASs and soil pathogens, these processes contribute the coexistence and diversity of plant species in this stage when most soil nutrients have a very low availability. We propose that it is necessary to quantify the relationships between changes in soil nutrient availability (including concentrations and fractions) and plant NASs with soil age. More studies are also needed to quantify contributions of NASs to primary succession, diversity of plant species and soil development.
Arbuscular mycorrhizal (AM) fungi are a group of soil-dwelling fungi that can form symbiotic associations with most terrestrial plants. The extraradical mycelium can colonize different plant roots in addition to hyphal fusion, thus form extensive arbuscular mycorrhizal networks (AMNs) underground. AMNs can transport and recycle water and nutrients including carbon, nitrogen, phosphorus among plants, recent evidences show that AMNs can also transfer defensive signals to neighboring plants when plants suffer environmental stresses, thus providing early warning to surrounding neighbors. However, the research on AMNs-mediated signal transfer is still in its infancy. Here, we firstly reviewed current research progresses in this research area, then proposed the unanswered questions that worth exploration in the future, including the possible pathways and mechanisms of signal transfer via AMNs among plants, the possible regulation of mycorrhizal symbionts by AMNs-mediated signal transfer, and the common techniques and their development used in the study of AMNs. Finally, we discussed about the possible ecological applications of AMNs such as filed crop protection.
Aims The formation of the geographical range boundary of species has always been an important topic in evolutionary biology. Although plant-microbe interactions have been extensively studied, we have a poor understanding of how plant's geographic range limits affect soil microorganisms. Cephalostachyum pingbianense is a rare bamboo species documented that produces bamboo shoots all year round in the wild, and is endemic to southeast Yunnan Province, China. The species is of great significance to study narrow endemic species in Bambusoideae. Here, we aim to reveal the relationship between the range limits of C. pingbianenseand soil fungal community.
Methods We assayed soil physical and chemical properties at the center, edge and beyond the range of C. pingbianense, and changes of fungal community were analyzed by means of Internal Transcribed Spacer (ITS) sequence based Illumina MiSeq high-throughput sequencing techniques.
Important findings (1) Soil pH and available phosphorus content at the range edges was significantly lower than other sites. (2) At the range center, species diversity of soil fungi was the highest, and relative abundance of Mortierella was significantly higher than other sites. At the range edges, species diversity of soil fungi was the lowest, and relative abundance of Basidiomycota was greater than 65.0%. (3) Soil pH played a crucial role in driving the variation of fungal community, which was negatively correlated with the relative abundance of ectomycorrhizal fungi, and positively correlated with the relative abundance of saprophytic fungi. Soil acidification and phosphorus deficiency may be important soil properties controlling the distribution range of C. pingbianense. Mortierella may be important mutualists of C. pingbianense, which can desorb phosphorus from soil minerals and reduce acidification of soil.
Orchid is typical of mycorrhizal plants. Orchid mycorrhiza (OM), the symbiotic association between orchid roots and fungi, is unique to orchids. The nutrient sources of orchid mycorrhizal fungi (OMF) affect the lifestyle and nutrient levels of its host plants. Nitrogen (N) is the main limiting factor of plant growth. Orchids generally have higher tissue N levels compared to neighbor autotrophic plants, meaning N enrichment of plants. This paper reviewed the types and taxa of OMF, N nutrition characteristics of orchids, and N transfer mechanism in OM to provide a reference for the research on protection, regeneration, and sustainable utilization of orchid resources.
Aims Phosphorus is one of the major limiting nutrients for plant growth in subtropical areas, whereas increasing nitrogen deposition may be a limiting factor in determining the availability of soil phosphorus. Here, focusing on soil microorganisms and plant fine roots, we explored the transformation of soil phosphorus to unravel the maintenance of soil phosphorus supply and plant productivity with low availability under nitrogen deposition.
Methods At the Fuzhou Changʼan Mountain in Fujian Province, China, control (0 kg·hm-2·a-1), low nitrogen (40 kg·hm-2·a-1), and high nitrogen (80 kg·hm-2·a-1) treatments were set up to simulate nitrogen addition. Soil and root samples of Cunninghamia lanceolata seedlings were then collected to comprehensively analyze soil phosphorus and nutrient contents as well as microbiological-plant root characteristics.
Important findings The results showed that the contents of soil labile organic phosphorus, moderately labile inorganic phosphorus and occluded phosphorus were significantly increased, whereas those of primary mineral phosphorus and moderately labile organic phosphorus decreased under the low nitrogen treatment as compared to the control treatment. However, there were no significant changes under the high nitrogen treatment. Redundancy analysis indicated that soil acid phosphatase activity, relative abundance of mycorrhizal fungi, soil microbial biomass phosphorus content, and root biomass were important soil microbiological-plant root characteristics factors that could explain the changes in soil phosphorus components. Variance partitioning analysis revealed that the soil microbiological-plant root characteristics synergy explained 57% of the alternations in soil phosphorus components, whereas correlation analysis showed a significant positive correlation between the relative abundance of mycorrhizal fungi and root biomass. Overall, these results suggest that mycorrhizal colonization is promoted under a low level of nitrogen input and the synergistic action of mycorrhizal fungi and C. lanceolata fine roots promotes the conversion of moderately labile organic and primary mineral phosphorus to labile phosphorus, thus maintaining the growth of C. lanceolata seedlings.
Aims Root hairs and mycorrhizal fungi, by increasing absorbing area of plant roots, promote ability of plants in acquiring soil resources such as phosphorus (P). The combination of absorptive roots, root hairs, and mycorrhizal fungi differs among distinct plant species, resulting in variations in acquisition of soil resources. At present, in situ quantifications of microstructures on the surface of roots is difficult, and relationships among absorptive roots, root hairs, and mycorrhizal fungi underlying the adaptation of soil P gradient in different woody plants remain largely unknown.Methods We investigated 21 tree species in a subtropical forest and examined the existence of root hairs. We quantified the variation of root hair characteristics and analyzed the relationships between root hairs, mycorrhizal colonization rate, root traits along with soil P availability.Important findings 1) Root hairs did not commonly exist in 21 subtropical tree species. We only observed root hairs in seven species, including four arbuscular mycorrhizal (AM) trees and three ectomycorrhizal (ECM) trees. Root hair occurrence rate was highest in Pinus massoniana (86%). 2) Mycorrhizal type is key to understanding the relationships between root hairs and mycorrhizal fungi. Root hair density was significantly positively correlated with mycorrhizal fungi colonization rate in AM trees. In contrast, in ECM trees, root hair diameter was significantly negatively correlated with mycorrhizal fungi colonization rate. 3) Root hair length and diameter were negatively correlated with soil available P content in AM trees, while root hair occurrence rate decreased with the soil available P content in ECM trees. Our results improve the understanding of root hairs and their interaction with other plant traits in natural forest stands, which lay the foundation for better predictions of nutrient acquisition strategies.
Aims Phenols are organic components that are resistant to be decomposed during litter decomposition, and their initial content greatly affects the subsequent decomposition process. However, patterns of their initial content in plant litter at the global scale are unclear. In this paper, the content of total phenol and soluble phenol in litter and their response to climate, mycorrhizal association, life forms and soil properties were assessed at the global scale.Methods Data were collected from published scientific articles before November 5, 2021, the content and influencing factors of total and soluble phenol in plant litter were discussed at the global scale. Among them, 98 articles had total phenol content, covering 350 observations, and 18 articles had soluble phenol content, covering 70 observations. The linear mixed model was used to compare the differences of total phenol and soluble phenol content in root and leaf litter of different functional traits. The linear mixed model was also used to evaluate the effects of different environmental factors on total phenol and soluble phenol content in root and leaf litter. The linear mixed effect model selection method was used to further evaluate the relative importance of influencing variables on the initial total phenol and soluble phenol content in litter. Important findings Results showed that (1) The average initial total phenolic and soluble phenolic content of the global litter was 65 and 88 mg·g-1, respectively. (2) Mycorrhizal association had a significant effect on the total phenolic content in root litter and the soluble phenolic content in leaf litter. The total phenolic content in root litter of plants with both arbuscular mycorrhiza and ectomycorrhiza was significantly lower than that in litter of plants with ectomycorrhiza, while the soluble phenolic content in leaf litter of plants associated with both arbuscular mycorrhiza and ectomycorrhiza was significantly higher than that in litter from plants associated with arbuscular mycorrhiza. (3) Phylogenetic types (gymnosperm, angiosperm) and leaf morphology (needleleaf, broadleaf) had significant effects on the total phenolic content in leaf litter, and the total phenolic content in litter of broadleaf and angiosperm plants was significantly higher than that in litter of needleleaf and gymnosperm plants. (4) Average temperature diurnal range, precipitation in the driest month, and precipitation in the driest quarter were significantly positively correlated with the total phenolic content in leaf litter. (5) Precipitation in the warmest quarter and soil moisture were significantly negatively correlated with the content of soluble phenol in leaf litter. (6) Leaf morphology had the most significant effect on total phenolic content in leaf litter. Overall, these results will be useful for understanding the relationships between litter functional traits and phenols and for predicting the decomposition of plant litter under future climate change scenario.
Aims The aim of this research was to clarify the effects of intercropping and inoculation with arbuscular mycorrhizal fungi (AMF) on carbon transport and phosphorus uptake in black locust (Robinia pseudoacacia) and konjac (Amorphophallus konjac). The results could provide empirical evidence to reveal the mechanisms of black locust intercropping for disease control and plant growth promotion of konjac, and popularize the green and high-yielding cultivation technique of konjac under black locust.
Methods The experiment was carried out in two-compartment rhizoboxes separated by a 25-μm nylon net, each of which comprised compartment A (non-inoculated or AMF-inoculated black locust) and compartment B (monocropped black locust or intercropped konjac). A 13C stable isotope labeling technique was used to label the leaves of black locust in compartment A with 13CO2. Carbon transport from black locust to konjac and the effects of AMF colonization on agronomic traits, 13C abundance, and phosphorus content in both crops were investigated.
Important findings The result showed that: (1) After inoculation, the AMF infection rate of black locust and konjac plants by hyphal links in compartment B reached 47.1% and 60.4%, respectively. For black locust, this AMF infection rate was 14.1% lower than that of directly inoculated plants under monocropping. In the case of intercropping, the biomass (dry mass) of AMF-inoculated konjac plants was 9.7% (aboveground parts) and 36.2% (belowground roots) higher than that of non-inoculated plants. (2) Compared with the non-inoculated plants under monocropping, the carbon fixed by photosynthesis of black locust plants in other treatments (non-inoculated + intercropping, inoculated + monocropping, and inoculated + intercropping) was mainly allocated to the plant roots and rhizosphere soil in compartment A, and more carbon passed through the nylon net in the form of root exudates to reach the rhizosphere of neighboring crop plants. (3) Compared with the respective non-inoculated controls, AMF inoculation in the monocropping and intercropping systems prominently improved phosphorus contents in the leaves, stems/petioles, roots, and total plants of black locust and konjac in compartment B. The findings suggest that AMF colonization could facilitate carbon transport from black locust to the rhizosphere soil and plant tissues of konjac. Intercropping konjac with black locust is an effective practice to promote AMF colonization and phosphorus uptake by both host plants.
Arbuscular mycorrhiza (AM) is one of the oldest symbionts between plants and soil microorganisms, and about 80% terrestrial plant species can associate with AM fungi on earth. Because of the stable climate and poor soil phosphorus content in tropical and subtropical forests, this mutualistic symbiosis is much more common there. Previous studies have extensively investigated the diversity of AM fungi in tropical and subtropical forests, and have shown that AM fungi can promote plant recruitment and growth. However, this positive effect of AM fungi on plants (i.e., the positive plant-soil feedback) can weaken the contribution of the negative plant-soil feedback (caused by soil-borne pathogens) to maintaining tree species diversity, which appears to contradict with the surprisingly high tree diversity and high proportion of rare tree species in tropical and subtropical forests. Recently, a mounting number of empirical studies have found that the diversity of AM fungi varies significantly in different habitats and AM colonization depends on the identity of host species, thereby affecting the fitness of plants and further shaping the plant community structure. Through synthesizing the current research about the diversity of AM fungi in promoting plant coexistence and maintaining community diversity, we expect to put forward a promising study direction for testing the “rare species advantage” hypothesis, therefore improving the conservation of rare plant species.
Aims Fire is an important disturbance factor in the northern forest ecosystem, and black carbon, a product of fire, widely exists in most forest soils. Many studies have shown the positive impact of black carbon on plant yield, but little is known about the synergy between black carbon and microorganisms (such as mycorrhizal fungi) which can promote plant growth. Ectomycorrhiza (ECM) fungi is like a bridge between coniferous trees and soil in the northern forest ecosystem. Exploring the changes of ECM fungal community after fire can provide a theoretical basis for the carbon pool restoration and help with scientific management of the northern forest ecosystem after fire.
Methods In this study, Larix gmelinii forest in the Da Hinggan Mountains was taken as the research object. Samples were taken at the beginning of the growing season (June) and at the end of the growing season (September) after fire disturbance. ECM fungi were identified by high-throughput sequencing method to explore the changes and key influencing factors of ECM fungal community under the treatment of fire and black carbon addition.
Important findings The results showed that: (1) During the growing season, compared with CK, the α-diversity of ECM fungal community treated by fire decreased significantly by 31.52%, while it increased significantly by 49.02% under black carbon addition treatment. There were significant differences in the β-diversity of of ECM fungal community under fire and black carbon addition treatments during the growing season. (2) During the growing season, the abundance of ECM fungi treated by fire decreased significantly by 46.35%, but the fire treatment significantly increased Basidiomycetes species abundance, while black carbon addition treatment increased Ascomycetes and Basidiomycetes species abundance. (3) During the growing season, the composition of ECM fungal community in Larix gmelini forest was significantly affected by soil pH, water content and total nitrogen content under the fire and black carbon addition treatments, but it was positively correlated with soil pH and total nitrogen content and negatively correlated with soil water content in the black carbon addition treatment. The results of this study showed that fire reduced the diversity of ECM fungi in Larix gmelinii forest during the growing season, and significantly reduced the abundance of ECM fungi. However, the addition of black carbon after fire may change this negative effect. By affecting the changes of soil pH and soil nitrogen content, black carbon promoted the recovery of ECM fungi and increased its diversity. Therefore, the long-term impact of black carbon on ECM fungal community should be continuously monitored in the future.
Trade-offs among plant functional traits reflect the trade-off relationships between resource acquisition and conservation of different plants, which are of pivotal importance for understanding the mechanisms by which plants adapt to the environment. However, due to the heterogeneity of the soil environment and the limitations of technical means, the study of below-ground root functional traits and their interrelationships is currently lagging behind that of above-ground functional traits. Traditionally, fine roots have been defined as all roots ≤2 mm in diameter. The acquisition and utilization of soil resources by plants depends on architectural traits, morphological traits, chemical traits and biotic traits of fine roots and so on, including fine roots associations with mycorrhizal fungi. Recently, the root economics space has been proposed, which demonstrates the existence of trade-offs between the do-it-yourself strategy of plants increasing their own root surface area and the outsourcing strategy of investments into fungal symbionts for enhanced nutrient mobilization from hyphal expansion, in addition to the traditional trade-offs between fast (high nitrogen content and metabolic rate) and slow (high tissue density) investment return. It was found that thin-root species obtained soil resources mainly by increasing specific root length, whereas thick-root species relied more on mycorrhizal fungi. However, the carbon economy of resource acquisition through the root and mycorrhizal hyphal pathways remains unclear. In future research, the key issues of root functional traits were suggested as follows: 1) for research methods, it is urgent to establish a unified set of definitions and research methods for root classification, sampling, storage, functional traits and their research methods; 2) for research traits, the research of “hard” traits of fine roots should be strengthened; 3) for the trade-offs between functional traits of fine roots, it is of great significance to strengthen the study of the trade-offs between construction costs and resource benefits between plant roots and mycorrhizal fungi.
Aims This study aimed to illustrate community structure, molecular ecological network and driving factors of ectomycorrhizal fungi associated with Pinus sylvestris var. mongolica at different growth periods, and provide a theoretical basis for sustainable management of P. sylvestris var. mongolica plantation.Methods Pinus sylvestris var. mongolica with different tree ages (23, 33 and 44 a) in Mau Us Sandy Land were targeted. The species compositions, interaction and main drivers of ectomycorrhizal fungi at the early growth period (Apr.), vigorous growth period (July) and the late growth period (Sept.) were identified by field investigation and sampling, illumina high-throughput sequencing and molecular ecological network analysis, respectively.Important findings 1) The growth period had significant effect on the richness and Chao1 index of ectomycorrhizal fungi, with significantly higher Chao1 and Simpson diversity index in vigorous growth period than in early and late growth periods. The tree age had no significant effect on the ectomycorrhizal fungal diversity index. 2) In Mau Us Sandy Land, the ectomycorrhizal fungi associated with P. sylvestris var. mongolica were identified into 2 phyla, 4 classes, 7 orders, 18 families, and 28 genera. The dominant genera were Tomentella, Inocybe and Geopora at the early, vigorous and late growth periods, respectively. The Tomentella and Inocybe were the common indicator genera in both vigorous and late growth periods. 3) At the end of the growing season, the nodes and edges of the ectomycorrhizal fungal networks were the largest, indicating that the ectomycorrhizal fungal community was more complex and there was strong interaction between fungal species. 4) Soil pH and annual relative humidity were the key environmental factors that significantly affected the community composition of ectomycorrhizal fungi. Our results demonstrated that the diversity and community composition of ectomycorrhizal fungi were affected by the growth stage and tree age, with a stronger effect in growth stage than in tree age. The seasonal dynamic distribution of ectomycorrhizal fungi mainly depended on soil properties and climate conditions.
Plant-soil feedback experiment is an important way for studying plant-soil biota interactions. Plant growth can change soil physical, chemical, and biotic properties in ways that then alter subsequent plant performance, population fluctuation, and community dynamics. This process, referred to as “plant-soil feedback” (PSF), might play a key role in biodiversity maintenance, sustainable agriculture development, and ecological restoration. In this review, we first provide an overview of the concept and research methods of PSF. Second, we review the research progress of the role of PSF in the maintenance of plant species diversity, plant community succession, plant invasions and range shifts, ecological response to climate change, above- and below-ground multitrophic interactions, ecosystem restoration, and crop performance in different cropping systems. We suggest three directions for future PSF studies, including: (1) the transition from single-species to community-level interactions between plants and soil biota; (2) the test of PSF experiments in field conditions; (3) the expansion of theoretical knowledge into ecological practice.
JIPB
Journal of Plant Ecology
Journal of Systematics and Evolution
Biodiversity Science
Bulletin of Botany