Rooting plasticity in wild and cultivated Andean Chenopodium species under soil water deficit

Abstract

Rooting plasticity is critical for plants exploiting patchy soil-water resources, but empirical evidence remains controversial due to complex root/soil interactions in natural and agricultural environments. We compared cultivated and wild Chenopodium populations from distinct agroecological background to assess their rooting plasticity when exposed to contrasting wet-dry soil profiles in a controlled environment. Four treatments of increasing dryness were applied during 6 weeks in plants of Chenopodium hircinum, Chenopodium pallidicaule and two ecotypes (wet- and dry-habitat) of Chenopodium quinoa grown in rhizotrons. Root system architecture and growth were sequentially mapped. At the end of the experiment, plant and root morphological traits and dry biomass were measured. Contrary to the other two species, C. quinoa showed accelerated taproot growth in dry soil conditions. The dry-habitat C. quinoa ecotype showed consistently higher plant traits related to longer, coarser, and more numerous root segments which give it a faster taproot growth and sustained root branching at depth in dry soil. High rooting plasticity confers the advantage of fast root elongation and deep soil exploration under soil water deficit. Variation in intrinsic root traits and plastic responses among Chenopodium populations controls their root foraging capacity facing patchy soil-water resources.