The Measurement of Membrane Potential and NO3 Activity in Root Cells Using Ion-Selective Microelectr

Remobilisation of nitrate in plants, especially in vacuole of plant, is mostly related to the qua-lity of agricultural products and the high nitrogen use efficiency in plants. Ion-selective microelectrodes offer anon-destructive and non-interruptive method to measure NO-3 gradients and electric potential differences acrossboth the plasma membrane and tonoplast. Thus, a double-barrelled microelectrode backfilled with a mem-brane sensor for NO-3 embedded in poly vinyl chloride (PVC) can record the NO-3 activity in cytoplasm and vac-uole of a cell. This paper presented how to make this kind of microelectrode and how to do the intracellularmeasurements on intact plants. Our result showed that nitrate activity was about 2.7 mmol L-1 in cytoplasmwhile 70 mmol L-1 in vacuole, which implicated that vacuole was a pool of nitrate in plants.