The Main Pathways For Na~+ Uptake And Its Effect On Plant Na~+ Segregation Of Two Glycyrrhiza Species With Different Salt Tolerance

To understand the Na+ uptake and efflux meachanisms of Glycyrrhiza uralensis and Glycyrrhiza inflata.Two Glycyrrhiza species seedlings were cultured with hydroponics.The effect of an apoplastic pathway to sodium uptake by using the apoplastic tracer dye 8-hydroxy-l,3,6-pyrenetrisulphonic acid?PTS?;the symplast pathway to the uptake of Na+ and efflux was researched using different ion channels inhibitors.The main conclusions are as follews:?1?Na+ uptake by the apoplastic pathwayPTS was identified in the vascular tissue of roots using epifluorescence microscopy and measured by a fluorescence spectrometer.The regressions for sodium transport on PTS transport accounted for-2.061% of the variation in the Glycyrrhiza uralensis and-1.88% of the variation in the Glycyrrhiza inflata.This suggests that Na+ can move freely through the root tip and lateral root development site,enter the stele and be transported to the shoot via the transpiration stream,but the transpirational bypass flow is not of major importance in sodium uptake by Glycyrrhiza uralensis and Glycyrrhiza inflata.?2?Na+ uptake by the symplast pathwayIn Glycyrrhiza uralensis,Ca²⁺ signifycantly reduced Na+ uptake when plants were treated with 50 or 150 mmol/L NaCl.The inhibitors of K+ channels,TEA⁺?10 mmol/L?and Cs⁺?10mmol/L?significantly reduced Na+ uptake with 50 mmol/L NaCl tresatment.In contrast with 50 mmol/L NaCl tresatment.Ba²⁺?10 mmol/L?,TEA⁺?10mmol/L?and Cs⁺?10mmol/L?significantly reduced Na+ uptake upon 150 mmol/L NaCl treatment.In Glycyrrhiza inflata,Ca²⁺ did not have any signifycantly effect on the uptake of Na+ when plants were treated with 50 or 150 mmol/L NaCl.The inhibitors of K+ channels,TEA⁺?10 mmol/L?and Cs⁺?10mmol/L?not significantly reduced Na+ uptake,but Ba²⁺?10mmol/L?significantly reduced Na+ uptake with 50 mmol/L NaCl tresatment.In contrast with 50 mmol/L NaCl tresatment.Ba²⁺?10mmol/L?not significantly reduced Na+ uptake,TEA⁺?10mmol/L?and Cs⁺?10mmol/L?significantly reduced Na+ uptake upon 150 mmol/L NaCl treatment.The date suggests that Glycyrrhiza uralensis and Glycyrrhiza inflata adopted differently Na+ uptake of pathway.?1?In Glycyrrhiza uralensis,nonselective cation channels?NSCCs?and a low-affinity cation transporter?LCT1?are major pathways for Na+ entry into root cells,and we propose that two distinct low-affinity Na+ uptake pathways exist in Glycyrrhiza uralensis: Pathway 1 is sensitive to TEA⁺and Cs⁺,and mediates Na+ uptake under low salinities?50 mmol/L NaCl?;pathway 2 is sensitive to Ba²⁺,TEA⁺ and Cs2+and mediates Na+ uptake under high salinities?150 mmol/L NaCl?.?2?In Glycyrrhiza inflata,nonselective cation channels?NSCCs?and a low-affinity cation transporter?LCT1?aren't major pathways for Na+ entry into root cells,and we propose that two distinct low-affinity Na+ uptake pathways exist in Glycyrrhiza inflata: Pathway 1 is insensitive to TEA⁺or Cs⁺,but sensitive to Ba²⁺and mediates Na+ uptake under low salinities?50 mmol/L NaCl?;pathway 2 is insensitive to Ba²⁺,but sensitive to TEA⁺ and Cs2+and mediates Na+ uptake under high salinities?150 mmol/L NaCl?.?3?Na+ excretionNH₄VO₃?an inhibitor of plasma membrane H+-ATPase,it was investigated whether the cytosolic Na+ was extruded into the apoplast?did not have any signifycantly effect on the efflux of Na+ when plants were treated with 50 mmol/L NaCl.This could be that it has not caused a harm the two kinds of licorice with 50 mmol/L NaCl.But NH₄VO₃ reduced on the efflux of Na+ when plants were treated with 150 mmol/L NaCl,and reduced on the efflux of Na+ in Glycyrrhiza uralensis higher than Glycyrrhiza inflata,the date suggests that more sodium were extruded in Glycyrrhiza uralensis than Glycyrrhiza inflata.This could be that it leads to large inflows of sodium ions with 150 mmol/L NaCl,and it has caused a harm the two kinds of licorice with 150 mmol/L NaCl,but two licorice reduce this damage by sodium ion excretion.?4?Na+ content in leafWhether Glycyrrhiza uralensis were treated in low NaCl content or in high NaCl content,it has higher Na+ content in leaf than Glycyrrhiza inflata.The difference is that it attributes this to the lower level of Na+ uptake and the higher leavel of Na+ compartmentalization?Na+ were isolated in other parts of the plant besides the leaf?of Glycyrrhiza inflate than that of Glycyrrhiza uralensis with 50 mmol/L NaCl.And it attributes this to the higher leavel of Na+ compartmentalizationthan of Glycyrrhiza inflata than Glycyrrhiza uralensis with 150 mmol/L NaCl.