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Dryad

Root anatomy helps to reconcile observed root trait syndromes in tropical tree species

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Dec 26, 2021 version files 283.65 KB

Abstract

Studying the organization of functional traits in plant leaves and stems has revealed notable patterns linking function and form; however, evidence of similarly robust organization in root tissues remains controversial. We posit that anatomical traits in roots can provide insight on the overall organization of the root system. We hypothesize that A) size variation in the tissue outside the stele relates in a non-linear fashion with functional traits associated with direct resource uptake, including a negative relationship with root architectural traits; and B) similar relationships detected in tropical areas also hold true in other biomes.

We address our hypotheses using empirical data from 24 tropical tree species in French Guiana, including anatomical measurements in first order roots, and functional trait description for the entire fine root system. In addition, we compiled a global meta-analysis of root trait with 500+ forest species across tropical, subtropical and temperate forests.

Our results supported the expected non-linear relationships between cortical size and morphological traits, and a negative linear trend with architectural traits. We confirmed a global negative relationship between SRL, diameter and tissue density, suggesting similar anatomical constraints in root systems across woody plants. However the importance of factors vary across biomes, possibly related to the unequal phylogenetic representation of families across latitudes.

Our findings imply that the rhizocentric hypothesis can be a valuable approach to understand fine root trait syndromes and the evolution of absorptive roots in vascular plants.