Potassium and Nitrate Uptake and Cell Transmembrane Electropotential in Excised Pea Epicotyls'

A bsttract. In contrast to intact etiolated pea seedling tissue (Pisum sativum L.), excised segments immersed in a complete nutrient solution show marked increases in ion content, largely of K+ and NO.-, over a 72-hour period. During this time there is increase in cell electropotential difference, PD. During the initial 6 to 8 hours there is a lag in ion uptake; cell PD, however, increases rapidly from approximately -50 to -100 mv then increases more slowly. The increase in PD precedes and thus may be a prerequisite for the rapid ion accumulation phase. Cell PD increases in either water or nutrient solution but eventually reaches higher levels in the latter. Following water pretreatment of sufficient duration K+ accumulation shows no lag period. The lag phase noted here appears dlissimilar to that of storage tissues.