Faster acquisition of symbiotic partner by common mycorrhizal networks in early plant life stage

Sandra Varga,Minna‐Maarit Kytöviita

doi:10.1002/ecs2.1222

Abstract

AbstractArbuscular mycorrhizal (AM) fungi usually improve plant performance yet our knowledge about their effects on seed germination and early plant establishment is very limited. We performed a factorial greenhouse experiment where the seeds from four low Arctic co‐occurring mycorrhizal herbs (Antennaria dioica, Campanula rotundifolia, Sibbaldia procumbens, and Solidago virgaurea) were germinated alone or in the vicinity of an adult Sibbaldia plant with or without AM fungi; given either as spores or being present in a common mycorrhizal network (CMN). Three different AM fungal species were examined to assess species‐specific differences in symbiont acquisition rate. Of the four plant species investigated, the presence of AM fungi affected seed germination only in Campanula and this effect was dependent on whether the AM fungi were present in the soil as spores or as a CMN. Overall, after germination, developing seedlings showed AM fungal colonization in their roots as soon as 2 d after cotyledon emergence. Our results show that CMN may provide germinating seedlings faster acquisition of the AM fungal partner in comparison to acquisition from spores. Furthermore, there were AM species‐specific differences in the symbiont acquisition rate highlighting the importance of species identity in AM interactions. These findings suggest that while AM fungi may not play a fundamental role during seed germination, plant community composition may be affected by the species‐specific AM fungal effects on seedling establishment and CMN acquisition.

Highlights

Our knowledge of the role of mycorrhizal symbiosis on the early part of plant life cycle is very limited in contrast with the well-established effects of mycorrhizal symbioses on plant growth and reproduction later in plant life (Koide 2000, Smith and Read 2008)
The effects of the common mycorrhizal network (CMN) on seed germination varied among Arbuscular mycorrhizal (AM) fungal species as shown by the significant interaction between these two factors (Table A1)
The presence of an established Sibbaldia decreased the overall proportion of germinating Solidago seeds (Table 1, Fig. 1B) and decreased seed germination of conspecific Sibbaldia (Table 1, Fig. 1C), while no significant differences among fungal treatments or an interaction between these two factors were detected (Table 1)

Summary

Introduction

Our knowledge of the role of mycorrhizal symbiosis on the early part of plant life cycle is very limited in contrast with the well-established effects of mycorrhizal symbioses on plant growth and reproduction later in plant life (Koide 2000, Smith and Read 2008). In most plant communities, seedling recruitment is limited by several abiotic and biotic factors including competition from established vegetation 2004) and seed germination and seedling establishment will partly determine community composition. In natural communities, developing seedlings may immediately contact with arbuscular mycorrhizal (AM) fungi present in the soil. AM fungi are ubiquitous symbiotic organisms growing in association with the roots of 73% of angiosperms (Brundrett 2009). AM fungi may connect roots of several coexisting plant individuals forming the so-c alled common mycorrhizal network (CMN, Newman 1988).

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Discussion

Conclusion