Root Hydraulic and Aquaporin Responses to N Availability

Abstract

Nitrogen (N) uptake in most plants is positively correlated to water flow in and through roots. This allows transpiration to drive convection of mobile N sources in the soil to the root surface. Generally N starvation suppresses root hydraulic conductivity (Lp(r)) while resupply stimulates. However, ammonium and nitrate can give different responses depending on the species, and this may be associated with the form of N that different species prefer to transport and assimilate. Responses in Lpr in the short to medium term are largely explained by aquaporin regulation at both the transcript and post-translational level. Local and systemic signalling is indicated in the regulation of aquaporins. A direct role for NO3 sensing has been shown as well as a role of a high-affinity NO3- transporter (NRT2.1), but the mode of action in post-translational modification is not known. Transcripts of the aquaporins are also altered by N treatments, yet the regulations of these transcripts and the function of the proteins in N transport remain unclear. Further research is required to uncover the signalling and regulation of aquaporins in relation to N transport since modifications to this process may improve N use efficiency.