Mechanism of Low NO3-Stress Inhibiting Apoplastic Transport in Tobacco Roots
To explore how low NO3-stress affects the apoplastic pathway transport in tobacco root,two low NO3-stress treatments were implemented at concentrations of 0.01 and 0.1 mmol/L,while 4.0 mmol/L NO3-treatment served as the control.The flue-cured tobacco variety Zhongyan100 was employed as the experimental material.Various parameters including tobacco seedling development,root morphology,transpiration rate,apoplastic pathway transport,endodermal suberization,and gene expression related to apoplastic barrier formation were analyzed.The root/shoot of low NO3-stress(0.01 mmol/L and 0.1 mmol/L)was significantly higher than that of the control,with increases of 267％and 125％,respectively;The transpiration capacity of low NO3-stress was significantly lower than that of the control,with decreases of 176％and 114％,respectively;The PTS fluorescence intensity of low NO3-stress is significantly lower than that of the control,with the decrease of 31％and 27％,respectively.The PTS concentrations in xylem sap and shoot of low NO3-stress exhibited lower than that of the control,with the decrease of 105％,91％and 103％,75％,respectively.Moreover,low NO3-stress induced early endodermal suberization of tobacco roots,with suberin deposition observed nearer to the root tip.This stress condition meanwhile upregulated gene expression associated with apoplastic barrier formation.In summary,low NO3-stress-induced endodermal suberization inhibited the apoplastic pathway transport in tobacco roots.
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