Hamard, S. | bioRxiv Science

bioRxiv2021

Environmental stress determines the colonization and impact of an endophytic fungus on invasive knotweed

O_LIThere is increasing evidence that microbes play a key role in some plant invasions. A diverse and widespread but little understood group of plant-associated microbes are the fungal root endophytes of the order Sebacinales. They are associated with exotic populations of invasive knotweed (Reynoutria ssp.) in Europe, but their effects on the invaders are unknown. C_LIO_LIWe used the recently isolated Sebacinales root endophyte Serendipita herbamans to experimentally inoculate invasive knotweed and study root colonisation and effects on knotweed growth under different environmental conditions. We verified the inoculation success and fungal colonisation through immunofluorescence microscopy and qPCR. C_LIO_LIWe found that S. herbamans strongly colonized invasive knotweed in low-nutrient and shade environments, but much less under drought or benign conditions. At low nutrients, the endophyte had a positive effect on plant growth, whereas the opposite was true under shaded conditions. C_LIO_LISynthesis. Our study demonstrates that the root endophyte S. herbamans has the potential to colonize invasive knotweed fine roots and impact its growth, and it could thus also play a role in natural populations. Our results also show that effects of fungal endophytes on plants can be strongly environment-dependent, and may only be visible under stressful environmental conditions. C_LI

ecology↗

bioRxiv2020

Morphological and biochemical responses of Sphagnum mosses to environmental changes

* Background and AimsSphagnum mosses are vital for peatland carbon (C) sequestration, although vulnerable to environmental changes. For averting environmental stresses such as hydrological changes, Sphagnum mosses developed an array of morphological and anatomical peculiarities maximizing their water holding capacity. They also produce plethora of biochemicals that could prevent stresses-induced cell-damages but these chemicals remain poorly studied. We aimed to study how various anatomical, metabolites, and antioxidant enzymes vary according to Sphagnum taxonomy, phylogeny and environmental conditions. * MethodsWe conducted our study in five Sphagnum-dominated peatlands distributed along a latitudinal gradient in Europe, representing a range of local environmental and climate conditions. We examined the direct and indirect effects of latitudinal changes in climate and vegetation species turnover on Sphagnum anatomical (cellular and morphological characteristics) and biochemical (spectroscopical identification of primary and specialized metabolites, pigments and enzymatic activities) traits. * Key resultsWe show that Sphagnum traits were not driven by phylogeny, suggesting that taxonomy and/or environmental conditions prevail on phylogeny in driving Sphagnum traits variability. We found that moisture conditions were important determinants of Sphagnum anatomical traits, especially those related to water holding capacity. However, the species with the highest water holding capacity also exhibited the highest antioxidant capacity, as showed by the high flavonoid and enzymatic activities in their tissues. Our study further highlighted the importance of vascular plants in driving Sphagnum biochemical traits. More particularly, we found that Sphagnum mosses raises the production of specific compounds such as tannins and polyphenols known to reduce vascular plant capacity when herbaceous cover increases. * ConclusionsOur findings show that Sphagnum anatomical and biochemical traits underpin Sphagnum niche differentiation through their role in specialization towards biotic stressors, such as plant competitors, and abiotic stressors, such as hydrological changes, which are important factors governing Sphagnum growth.

ecology↗