Local and systemic metabolic adjustments to drought in maize: Hydraulic redistribution in a split-root system

Background It is yet unknown how maize plants respond to a partial root drying under conditions of a limited total water supply, and which adaptation mechanisms are triggered under these conditions. Aims The aims of this study were to assess whether partial root drying results in distinguishable local and systemic physiological and metabolic drought responses, and whether compensatory water uptake and/or alteration of root architecture occurs under these conditions. Methods Maize plants were grown in a split-root system. When plants were 20 days old, the treatments 'well-watered', 'local drought' and 'full drought' were established for a period of 10 days. Shoot length and gas exchange were measured non-destructively, root exudates were collected using a filter system and biomass, relative water content, osmolality and proline content were determined destructively at final harvest. Results Local drought triggered stress responses such as reduced biomass, shoot length, relative water content and increased osmolality. Maintained root growth was systemically achieved by hydraulic redistribution rather than by altering root architecture. Local and systemic osmolyte adjustments contributed to this hydraulic redistribution. Conclusions Both local and systemic metabolic responses helped the plants to induce hydraulic redistribution, enhance water availability and in consequence plant water relations. This resulted in a surprisingly well-maintained root growth even in the drought stressed root compartment.

Automated summary

This study assessed the response of maize plants to partial root drying under conditions of limited water supply. It found that there were distinguishable local and systemic physiological and metabolic responses to drought. The study also demonstrated that root growth was maintained through hydraulic redistribution rather than alteration of root architecture.