Tracking plant preference for higher‐quality mycorrhizal symbionts under varying CO₂ conditions over multiple generations

Abstract

The symbiosis between plants and root‐colonizing arbuscular mycorrhizal (AM) fungi is one of the most ecologically important examples of interspecific cooperation in the world. AM fungi provide benefits to plants; in return plants allocate carbon resources to fungi, preferentially allocating more resources to higher‐quality fungi. However, preferential allocations from plants to symbionts may vary with environmental context, particularly when resource availability affects the relative value of symbiotic services. We ask how differences in atmospheric CO 2‐levels influence root colonization dynamics between AMF species that differ in their quality as symbiotic partners. We find that with increasing CO 2‐conditions and over multiple plant generations, the more beneficial fungal species is able to achieve a relatively higher abundance. This suggests that increasing atmospheric carbon supply enables plants to more effectively allocate carbon to higher‐quality mutualists, and over time helps reduce lower‐quality AM abundance. Our results illustrate how environmental context may affect the extent to which organisms structure interactions with their mutualistic partners and have potential implications for mutualism stability and persistence under global change.

Mycorrhizal Fungi Respond to Resource Inequality by Moving Phosphorus from Rich to Poor Patches across Networks

“…For all whole plant experiments, we used Medicago truncatula Gaertn. (courtesy of Prof. B. Hause, Leibniz Institute of Plant Biochemistry, Halle, Germany) as a host and germinated seeds as described [ 42 , 43 ]. After germination, we transferred the seeds to pots containing 160 g autoclaved seedling soil, and cultivated them in a climate-controlled room (16 hours in the light at 22°C interspersed by 8 hours in the dark at 17°C; 75% humidity).…”

Unity in diversity: structural and functional insights into the ancient partnerships between plants and fungi

“…In such experiments, fungal-acquired nutrient transfer to the plant is not always linked in a linear manner to plant C transfer Field et al, 2012Field et al, , 2015aField et al, , 2016aZhang et al, 2015). A common limitation is that single growth chambers for each CO 2 condition are often used in these experiments, raising the possibility that observations occur through chamber effects rather than solely CO 2 effects (Werner et al, 2018). Future studies must seek to reduce similar pseudoreplication by multiple chambers for each CO 2 treatment, or by rotating plants and CO 2 conditions between paired growth chambers (e.g.…”

“…Both Glomeromycotina and Mucoromycotina fungi (and dual fungal symbioses involving both fungal partners) gain a greater proportion of recently fixed photosynthates when grown under an elevated atmospheric [CO 2 ] compared to current ambient conditions (Drigo et al, 2010;Field et al, 2012Field et al, , 2015bField et al, , 2016a, decreasing further in response to subambient atmospheric [CO 2 ] (Zhang et al, 2015). Nutrient transfer from fungus to plant appears to respond differently to changing [CO 2 ] according to both fungal and plant host identity (Field et al, 2012(Field et al, , 2015b(Field et al, , 2016aWerner et al, 2018). For instance, Glomeromycotina-associated nonvascular plants exposed to elevated atmospheric [CO 2 ] assimilate more fungal-acquired 33 P tracer than under ambient atmospheric [CO 2 ] (Field et al, 2012;Werner et al, 2018).…”

“…Nutrient transfer from fungus to plant appears to respond differently to changing [CO 2 ] according to both fungal and plant host identity (Field et al, 2012(Field et al, , 2015b(Field et al, , 2016aWerner et al, 2018). For instance, Glomeromycotina-associated nonvascular plants exposed to elevated atmospheric [CO 2 ] assimilate more fungal-acquired 33 P tracer than under ambient atmospheric [CO 2 ] (Field et al, 2012;Werner et al, 2018). By contrast, 33 P tracer uptake via fungal symbionts in vascular plants appears to be either maintained across CO 2 treatments, or is reduced under the higher [CO 2 ] (Field et al, 2012).…”

Carbonic anhydrases CA1 and CA4 function in atmospheric CO2-modulated disease resistance

“…Furthermore, exposure of the model plant species Arabidopsis thaliana (hereafter Arabidopsis) to pre-industrial, current and future levels of atmospheric CO 2 uncovered marked effects on plant immunity against diverse (hemi) biotrophic and necrotrophic pathogens (Mhamdi and Noctor 2016;Zhou et al 2017Zhou et al , 2019Willams et al 2018b). Changes in atmospheric CO 2 levels not only affect plant-pathogen interactions, but also impact the interaction of plants with mutualistic mycorrhizal fungi and plant growth-promoting rhizobacteria (Werner et al 2018;Williams et al 2018a). Hence, to produce climate resilient crops in the future, it is important to understand how changes in atmospheric CO 2 levels impact plant-microbe interactions.…”