Root system architecture in Arabidopsis grown in culture is regulated by sucrose uptake in the aerial tissues.

This article presents a detailed model for the regulation of lateral root formation in Arabidopsis thaliana seedlings grown in culture. We demonstrate that direct contact between the aerial tissues and sucrose in the growth media is necessary and sufficient to promote emergence of lateral root primordia from the parent root. Mild osmotic stress is perceived by the root, which then sends an abscisic acid-dependent signal that causes a decrease in the permeability of aerial tissues; this reduces uptake of sucrose from the culture media, which leads to a repression of lateral root formation.

Identification of quantitative trait loci that regulate Arabidopsis root system size and plasticity.

Root system size (RSS) is a complex trait that is greatly influenced by environmental cues. Hence, both intrinsic developmental pathways and environmental-response pathways contribute to RSS. To assess the natural variation in both types of pathways, we examined the root systems of the closely related Arabidopsis ecotypes Landsberg erecta (Ler) and Columbia (Col) grown under mild osmotic stress conditions.

Osmotic regulation of root system architecture.

Although root system architecture is known to be highly plastic and strongly affected by environmental conditions, we have little understanding of the underlying mechanisms controlling root system development. Here we demonstrate that the formation of a lateral root from a lateral root primordium is repressed as water availability is reduced. This osmotic-responsive regulatory mechanism requires abscisic acid (ABA) and a newly identified gene, LRD2.