Antagonism of chloride and nitrate inhibits nitrate reductase activity in chloride-stressed maize

Lars Eigner,Xudong Zhang,Christian Zörb,Bastian L Franzisky,Christoph‐Martin Geilfus

doi:10.1007/s10725-020-00685-2

Lars Eigner, Xudong Zhang + Show 3 more

Open Access

https://doi.org/10.1007/s10725-020-00685-2

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Abstract

Chloride (Cl−) is required for photosynthesis and regulates osmotic balance. However, excess Cl− application negatively interacts with nitrate ({mathrm{NO}}_{3}^{-}) uptake, although its effect on {mathrm{NO}}_{3}^{-} 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 CaCl2), moderate Cl− (10 mM CaCl2), high Cl− (60 mM CaCl2). 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 CaCl2), which was 57% of the osmotic pressure being produced by 60 mM CaCl2. 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}^{-}.

Highlights

Salt stress caused by, for example, NaCl is a serious abiotic threat that imposes negative impacts on crop yield and the quality of plant products (Abdelaal et al 2020; Naeem et al 2020; Zörb et al 2019)
No significant difference in fresh weight could be observed between moderate C l− treatment and the control, except for the total shoot (Fig. 2a)
Negative effects of high C l− and osmotic treatment on dry weight were present in young tissue, old tissue, and shoots but not in roots (Fig. 2b)

Summary

Introduction

For example, NaCl is a serious abiotic threat that imposes negative impacts on crop yield and the quality of plant products (Abdelaal et al 2020; Naeem et al 2020; Zörb et al 2019). The unfavorable effects on plant growth are attributed to either osmotic stress or ion toxicity (Munns and Tester 2008). Chloride (Cl−) is the anion of NaCl and has multiple functions in plants (Geilfus 2018a; Wege et al 2017). Being a micronutrient (μM range), Cl− acts as a dominant functional element involved

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