Abstract

The mechanisms linking C/N balance to N uptake and assimilation are central to plant responses to changing soil nutrient levels. Defoliation and subsequent regrowth of grasses both impact C partitioning, thereby creating a significant point of interaction with soil N availability. Using defoliation as an experimental treatment, we investigated the dynamic relationships between plant carbohydrate status and NO3--responsive uptake systems, transporter gene expression, and nitrate assimilation in Lolium perenne L. High- and low-affinity NO3- uptake was reduced in an N-dependent manner in response to a rapid and large shift in carbohydrate remobilization triggered by defoliation. This reduction in NO3- uptake was rescued by an exogenous glucose supplement, confirming the carbohydrate dependence of NO3- uptake. The regulation of NO3- uptake in response to the perturbation of the plant C/N ratio was associated with changes in expression of putative high- and low-affinity NO3- transporters. Furthermore, NO3- assimilation appears to be regulated by the C-N status of the plant, implying a mechanism that signals the availability of C metabolites for NO3- uptake and assimilation at the whole-plant level. We also show that cytokinins may be involved in the regulation of N acquisition and assimilation in response to the changing plant C/N ratio.

Keywords

Carbohydrate; carbon; cytokinin; fructan; Lolium perenne; nitrate transporter (NRT); nitrate uptake; nitrogen; nitrogen use efficiency (NUE); perennial ryegrass

Published in

Journal of Experimental Botany
2017, Volume: 68, number: 7, pages: 1569-1583
Publisher: OXFORD UNIV PRESS

SLU Authors

• Späth, Jana

  • Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
    
  • Umeå University

UKÄ Subject classification

Botany


Publication identifier

DOI: https://doi.org/10.1093/jxb/erx056

Permanent link to this page (URI)

https://res.slu.se/id/publ/82822