Antagonism of chloride and nitrate inhibits nitrate reductase activity in chloride-stressed maize
Xudong Zhang, Bastian L. Franzisky, Lars Eigner, Christoph‐Martin Geilfus, Christian Zörb
Abstract
Abstract Chloride (Cl − ) is required for photosynthesis and regulates osmotic balance. However, excess Cl − application negatively interacts with nitrate ( $${\mathrm{NO}}_{3}^{-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>NO</mml:mi><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mo>-</mml:mo></mml:msubsup></mml:math> ) uptake, although its effect on $${\mathrm{NO}}_{3}^{-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>NO</mml:mi><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mo>-</mml:mo></mml:msubsup></mml:math> metabolism remains unclear. The aim was to test whether Cl − stress disturbs nitrate reductase activity (NRA). A maize variety ( Zea mays L. cv. LG 30215) was hydroponically cultured in a greenhouse under the following conditions: control (2 mM CaCl 2 ), moderate Cl − (10 mM CaCl 2 ), high Cl − (60 mM CaCl 2 ). To substantiate the effect of Cl − stress further, an osmotic stress with lower intensity was induced by 60 g polyethylene glycol (PEG) 6000 L −1 + 2 mM CaCl 2 ), which was 57% of the osmotic pressure being produced by 60 mM CaCl 2 . Results show that high Cl − and PEG-induced osmotic stress significantly reduced shoot biomass, stomatal conductance and transpiration rate, but NRA was only decreased by high Cl − stress. The interference of NRA in chloride-stressed maize is supposed to be primarily caused by the antagonistic uptake of Cl − and $${\mathrm{NO}}_{3}^{-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>NO</mml:mi><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mo>-</mml:mo></mml:msubsup></mml:math> .