ß-Cyclocitral is a conserved root growth regulator.

Natural compounds capable of increasing root depth and branching are desirable tools for enhancing stress tolerance in crops. We devised a sensitized screen to identify natural metabolites capable of regulating root traits in Arabidopsis ß-Cyclocitral, an endogenous root compound, was found to promote cell divisions in root meristems and stimulate lateral root branching. ß-Cyclocitral rescued meristematic cell divisions in ccd1ccd4 biosynthesis mutants, and ß-cyclocitral-driven root growth was found to be independent of auxin, brassinosteroid, and reactive oxygen species signaling pathways. ß-Cyclocitral had a conserved effect on root growth in tomato and rice and generated significantly more compact crown root systems in rice. Moreover, ß-cyclocitral treatment enhanced plant vigor in rice plants exposed to salt-contaminated soil. These results indicate that ß-cyclocitral is a broadly effective root growth promoter in both monocots and eudicots and could be a valuable tool to enhance crop vigor under environmental stress.

X-Ray Computed Tomography Reveals the Response of Root System Architecture to Soil Texture.

Root system architecture (RSA) impacts plant fitness and crop yield by facilitating efficient nutrient and water uptake from the soil. A better understanding of the effects of soil on RSA could improve crop productivity by matching roots to their soil environment. We used x-ray computed tomography to perform a detailed three-dimensional quantification of changes in rice (Oryza sativa) RSA in response to the physical properties of a granular substrate. We characterized the RSA of eight rice cultivars in five different growth substrates and determined that RSA is the result of interactions between genotype and growth environment. We identified cultivar-specific changes in RSA in response to changing growth substrate texture. The cultivar Azucena exhibited low RSA plasticity in all growth substrates, whereas cultivar Bala root depth was a function of soil hardness. Our imaging techniques provide a framework to study RSA in different growth environments, the results of which can be used to improve root traits with agronomic potential.