Pulsatilla patens (Ranunculaceae), a perennial herb, is ectomycorrhizal in northeastern Poland and likely shares ectomycorrhizal fungi with Pinus sylvestris

Abstract

The sharing of species of ectomycorrhizal fungi (EMF) among different co-occurring host plant species could allow the formation of common mycorrhizal networks, which can alter plant-plant interactions and succession. Such sharing of EMF among woody species is thought to be common in many forests, but very few herbaceous plants form EMF, so they are assumed to be excluded from EMF networks in forests. We studied the EMF on roots of a common coniferous tree, Pinus sylvestris, and a co-occurring rare herbaceous perennial plant, Pulsatilla patens (Ranunculaceae), in northeastern Poland. We examined roots from co-occuring P. sylvestris and P. patens, visually classified EMF into morphotypes, studied tissue sections of mycorrhizal structures using compound microscopy, and used DNA sequencing to identify the fungi. On both host plant species, we observed EMF colonization, with colonized root tips exhibiting a swollen appearance, as well as a variety of colors and textures of fungal mycelium covering and emanating from those swollen tips. Sectioning and microscopic examination of an EMF morphotype common on P. patens confirmed the presence of a mantle and Hartig net, indicating the likely presence of functional ectomycorrhizal structures. The two most frequent EMF were Cenococcum geophilum and Piloderma olivaceum, and the latter was found to associate with both host plant species. Several EMF found here only on P. patens, including C. geophilum and two Russula species, are known from previous studies to also associate with P. sylvestris and other tree species. The observation of shared EMF between a coniferous tree and an understory herb indicates the potential for common mycorrhizal networks to alter interactions between these two species and may also indicate a unique way in which the distribution and abundance of a rare herbaceous plant may be influenced by shared mutualisms with a common co-occurring woody plant.

Resolving the mycorrhizal status of important northern hemisphere trees

“…Here we advocate using standard morphological definitions supplemented with data on nutritional benefits and the detection of well-known symbiotic partners whenever such data are available (Tedersoo and Brundrett 2017;Brundrett and Tedersoo 2018). We see that roughly once or twice per year, potential cases of truly novel associations are reported (e.g., Orchard et al 2017;Hoeksema et al 2018). Therefore, it is wise to retain some flexibility in the scope of our definitions of mycorrhizas due to our current limited knowledge, especially from poorly sampled habitats.…”

Dual‐mycorrhizal plants: their ecology and relevance

“…For example, Fraxinus is a tree genus that has traditionally been considered AM (Harley & Harley, 1987), but recent studies clearly show EM structures in some species, such as Fraxinus uhdei (Ambriz et al, 2010). Another example is the EM status of the perennial herb Pulsatilla patens that grows in Pinus sylvestris forests (Hoeksema et al, 2018). The roots of this herb had Hartig net and mantle from genuine ectomycorrhizas as a result of associations with Cenococcum geophilum and Piloderma olivaceum amongst other EM fungi (Hoeksema et al, 2018).…”

“…Another example is the EM status of the perennial herb Pulsatilla patens that grows in Pinus sylvestris forests (Hoeksema et al, 2018). The roots of this herb had Hartig net and mantle from genuine ectomycorrhizas as a result of associations with Cenococcum geophilum and Piloderma olivaceum amongst other EM fungi (Hoeksema et al, 2018). However, given the relatively small body of literature on dual-mycorrhizal status, we considered all types of studies ranging from lab experiments using pure AM or EM inoculum to sampling of roots from the field.…”

Dirt cheap: an experimental test of controls on resource exchange in an ectomycorrhizal symbiosis

“…Rhizopogon roseolus and P. arhizus (hereafter ‘Rhizopogon’ and ‘Pisolithus’ ) are common in pine forests of the southeastern United States, important for seedling establishment, and are early and thorough colonizers of pines, making them ideal for this seedling study. Identities of the fungal isolates used for inoculation, and of EM root tips from harvested seedlings, were confirmed through Sanger DNA sequencing and comparison of sequences with public databases (see Rúa et al ., 2015; Craig et al ., 2016; Rasmussen et al ., 2017; Hoeksema et al ., 2018).…”