Endophyte-Mediated Effects on the Growth and Physiology of Achnatherum sibiricum Are Conditional on Both N and P Availability

Abstract

The interaction of endophyte–grass associations are conditional on nitrogen (N) availability, but the reported responses of these associations to N are inconsistent. We hypothesized that this inconsistency is caused, at least in part, by phosphorus (P) availability. In this experiment, we compared the performance of endophyte-infected (EI) and endophyte-free (EF) Achnatherum sibiricum subjected to four treatments comprising a factorial combination of two levels of N (N+ vs. N−, i.e. N supply vs. N deficiency) and two levels of P (P+ vs. P−, i.e. P supply vs. P deficiency) availability. The results showed that A. sibiricum–Neotyphodium associations were conditional on both N and P availability, but more conditional on N than P. Under N+P− conditions, endophyte infection significantly improved acid phosphatase activity of EI plants, such that the biomass of EI plants was not affected by P deficiency (i.e. similar growth to N+P+ conditions), and resulted in more biomass in EI than EF plants. Under N−P+ conditions, biomass of both EI and EF decreased compared with N+P+; however, EI biomass decreased slowly by decreasing leaf N concentration more rapidly but allocating higher fractions of N to photosynthetic machinery compared with EF plants. This change of N allocation not only improved photosynthetic ability of EI plants but also significantly increased their biomass. Under N−P− conditions, EI plants allocated higher fractions of N to photosynthesis and had greater P concentrations in roots, but there was no significant difference in biomass between EI and EF plants. Our results support the hypothesis that endophyte–grass interactions are dependent on both N and P availability. However, we did not find a clear cost of endophyte infection in A. sibiricum.

Endophyte species influence the biomass production of the native grassAchnatherum sibiricum(L.) Keng under high nitrogen availability

“…Under LN conditions, this positive effect was weaker, while E+ plants did show a higher aboveground biomass than E− plants. This was similar to a previous study using A. sibiricum (Li Ren, Han, Yin, Wei, & Gao 2012). Under nitrogen deficiency, the N concentration was lower for E+ compared to E− plants; however, E+ plants had an elevated photosynthetic capacity.…”

“…Achnatherum sibiricum plants with a higher PNUE could be the result of investing relatively more of their N in photosynthetic machinery (Li et al. 2012). Previous reports have also indicated that organisms with a greater growth advantage in nutrient‐poor conditions are those that are able to modify their body nutrient content and increase the efficiency of nutrient use without major decreases in their growth rates (Elser et al., 2003; Mulder & Bowden, 2007).…”

Beneficial Interactions in the Rhizosphere

“…Mechanisms have not been tested but the authors speculate about increased P solubilisation. Li et al ( 2012 ) found an interaction between N and P availability for endophyte-grass symbiosis: the endophyte infection improved acid phosphatase activity of endophyte-plants but only when suffi cient nitrogen was available. Saprophytic fungi can stimulate organic matter decomposition and thus increase nutrient availability for the plants ( Buée et al 2009 ).…”

Effect of Endophyte Association with Brachiaria Species on Shoot and Root Morpho-physiological Responses under Drought Stress

“…Several studies have also reported greater number of tillers in endophyte-infected than endophyte-free plants of some genotypes in [6,18,25,33,34]. In contrast, Cheplick [35] found less number of tillers, leaf area and biomass in some endophyte-infected genotypes of perennial ryegrass than in endophyte-free plants under both irrigated and drought conditions.…”

“…Tropical forage grasses are grown on marginal lands with limited or no agricultural inputs and their growth and survival depends on a wide range of environmental stresses [16]. Previous studies have investigated the role of A. implicatum mainly for its biocontrol property against pathogens such as Drechslera fungal pathogen in Brachiaria and against Meloidogyne incognita in tomato [1,17,18]. There has not been any detailed study on the effects of A. implicatum on morpho-physiological responses of Brachiaria under drought stress conditions.…”