Interplay between nitrate and water in shaping root hydraulics
Nitrogen and water are resources that have been shown to have a major impact on crop yield.
Yet, despite their importance and suggestions of direct interplay between nitrogen and water
uptake, we tend to study water stress and nitrogen stress separately.
The major goal of this study is to investigate biophysical and biological bases for the nitrogen
induced hydraulic resistance changes in root system and the role of this phenomenon at the whole
We aim at identification of biochemical processes involved in nitrate-induced alteration of root
hydraulics and physiological significance of this nitrate water interaction at a whole plant level.
Characterization of this fundamental mechanism by which plants can acclimate to spatial and temporal
dynamics of resource availability is a key element for integrative approach to plant biology.
Our preliminary experiments suggested that changes in nitrate concentration in realistic (natural)
concentration can have a dominant effect on root hydraulics and can change water flux by several
folds. Reaching our goal requires a multi-scale approach linking study at molecular/cellular level
of nitrate induced cytosolic pH changes – using fluorescent probes and NMR spectrometry; nitrate-induced
changes in expression of aquaporins – using real time PCR, to analysis of a whole plant physiological
response to nitrate-water interaction – using root pressure chambers, split root system experiments
and xylem sap analysis. We present two hypotheses:
Fast changes of root hydraulic resistance in response to nitrate availability occur due to changes
in the cytosolic pH associated with the process of nitrate assimilation and transport that lead to
pH related gating of the aquaporins.
Nitrate induced changes in root hydraulic properties stimulate uptake of nitrate from dynamic,
heterogeneous soil environment.
The study is proposed in an open-ended style that opens the new research area in plant-environment
interaction. We expect that although it focuses on our specific hypothesis, it will generate new
questions and direction for future studies on nutrient-water interactions.