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The construction cost of roots is a key functional trait

The different plant strategies in the use of resources can be aligned on an economics spectrum, resulting from the trade-off between maximizing growth and resource capture (acquisitive strategy) versus the conservative strategy, with more protected organs of longer life span. Within this context, it is of great relevance to know the amount of photosynthate inverted by the plant on the construction of fine roots to explore the soil and uptake water and nutrients.

          A research team from the University of Cordoba, in collaboration with IRNAS-CSIC, CEBAS-CSIC and the University of Brandenburg-Cottbus, has studied the components of the construction costs (carbon, minerals and nitrogen concentrations) of the fine roots (< 2mm diameter) for 60 Mediterranean woody species.           The type of association with symbiotic microbes influenced on the contribution of different components in the root construction costs. Thus, the concentration of minerals was more important for the roots of plants associated with ectomycorrhizal fungi (EcM), while the organic nitrogen was dominant in roots associated with rhizobial N-fixing species. Therefore, the specific resource-use strategy associated to each type of symbiont modulate the trade-off between structural and metabolic compounds, during the building of roots.

Environmental conditions also influenced on the root construction costs. In nutrient-poor soils the energy spent per unit of root mass by plants was greater than the root cost in more fertile and favourable conditions. Plant species able to tolerate stress caused by water and nutrient scarcity often have a conservative strategy in the use of resources, with more costly roots of longer life span.   

In conclusion, the root construction cost is a key functional trait for terrestrial plants, related with their strategies in the use of resources, the type of associations with symbiotic microorganisms, and with the availability of soil water and nutrients.

This study has been published on line the 7 February 2021 in the Journal of Ecology:

de la Riva EG, Prieto I, Marañón T, Pérez‐Ramos IM, Olmo M, Villar R (2021). Root economics spectrum and construction costs in Mediterranean woody plants: The role of symbiotic associations and the environment. Journal of Ecology , 109: 1873-1885.‐2745.13612

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