Mechanistic understanding of interspecific interaction between a C4 grass and a C3 legume via arbuscular mycorrhizal fungi, as influenced by soil phosphorus availability using a ¹³C and ¹⁵N dual‐labelled organic patch

Abstract

SUMMARY Arbuscular mycorrhizal fungi (AMF) can improve plant nutrient acquisition, either by directly supplying nutrients to plants or by promoting soil organic matter mineralization, thereby affecting interspecific plant relationships in natural communities. We examined the mechanism by which the addition of P affects interspecific interactions between a C4 grass (Bothriochloa ischaemum, a dominant species in natural grasslands) and a C3 legume (Lespedeza davurica, a subordinate species in natural grasslands) via AMF and plant growth, by continuous 13C and 15N labelling, combined with soil enzyme analyses. The results of 15N labelling revealed that P addition affected the shoot uptake of N via AMF by B. ischaemum and L. davurica differently. Specifically, the addition of P significantly increased the shoot uptake of N via AMF by B. ischaemum but significantly decreased that by L. davurica. Interspecific plant interactions via AMF significantly facilitated the plant N uptake via AMF by B. ischaemum but significantly inhibited that by L. davurica under P‐limited soil conditions, whereas the opposite effect was observed in the case of excess P. This was consistent with the impact of interspecific plant interaction via AMF on arbuscular mycorrhizal (AM) benefit for plant growth. Our data indicate that the capability of plant N uptake via AMF is an important mechanism that influences interspecific relationships between C4 grasses and C3 legumes. Moreover, the effect of AMF on the activities of the soil enzymes responsible for N and P mineralization substantially contributed to the consequence of interspecific plant interaction via AMF for plant growth.

Indigenous Microorganisms Offset Arbuscular Mycorrhizal Fungi-Induced Plant Growth and Nutrient Acquisition Through Negatively Modulating the Genes of Phosphorus Transport and Nitrogen Assimilation

“…In addition, AM fungi could assist plants to expand their nutrient absorption area via hyphae and thus pass through the P depletion zone around the rhizosphere, which is formed due to the low fluidity and solubility of phosphorus ( Bucher, 2007 ). Second, AM fungi can secrete soil enzymes, such as urease, leucine aminopeptidase, and alkaline phosphatase to mineralize the organic nutrients and dissociate the insoluble nutrients, thereby increasing plant nutrient absorption to promote plant growth ( Burke et al, 2011 ; Li et al, 2017 ; Liu et al, 2021 ). Furthermore, AM fungi significantly decreased the N/P ratio of B. tripartita from 26.38 to 16.53 by increasing the accumulation of P in this experiment ( Figure 1C ), which indicated that AM fungi are more effective in assisting plants to obtain P than N and native plant B. tripartita may be limited by P in karst areas without AM fungi, according to Koerselman and Meuleman (1996) who reported that plants with an N/P ratio greater than 16 are thought to be mainly limited in growth by P. This result is consistent with previous research which showed that AM fungi reduced N/P ratio of the host plant by promoting P absorption, resulting in P no longer being the main limiting factor of plant growth ( Shen et al, 2020 ).…”

Implications of plant N/P stoichiometry influenced by arbuscular mycorrhizal fungi for stability of plant species and community in response to nutrient limitation

“…The AMF hyphae preferentially grow towards organic matter patches and release bioavailable C into the surrounding soil at relatively low concentrations, priming the growth and extracellular enzyme production of rhizosphere microbes (Hodge et al 2001, Toljander et al 2007, Drigo et al 2010, Cheng et al 2012, Nuccio et al 2013, Bukovská et al 2018. We found that the interaction between AMF and soil microbes largely enhanced the positive effect of AMF on soil microbial extracellular enzyme activities involved in the mineralisation of soil organic N under soil N-poor conditions (data shown in Liu et al 2021a), improving soil N availability for plant growth.…”

“…3). Specifically, high levels of P addition largely promoted the benefits of AMF for P concentration in legumes but had little effect on that for N concentration (data was shown in Liu et al 2021a). This indicated that AMF alleviated P limitation for legume growth under soil P-poor conditions and was beneficial for the P uptake of legumes under soil N-poor conditions (Johnson et al 2015).…”

“…2). After substantial P addition, soil N availability limits plant growth (Liu et al 2021a). In contrast to C4 grasses, legumes can form tripartite symbiotic relationships with rhizobia (N-fixing bacteria) and AMF, which can use root nodules to sequester atmospheric N in rhizosphere soil (Unkovich et al 2008).…”

Soil legacy effects and plant—soil feedback contribution to secondary succession processes

“…During the life cycle, plant height was measured every month starting from May 20, 2018. After 4 months of plant growth (when the maximum biomass was reached [Liu et al 2021]), five pots were randomly selected for each treatment to collect plant and soil samples. In addition, the shoots and roots of the remaining potted plants were removed.…”