title: Phosphate Uptake by Excised Maize Root Tips Studied by in VivoP Nuclear Magnetic Resonance Spectroscopy.
abstract: The extent of phosphate uptake measured by the relative changes in cytoplasmic Pi, vacuolar Pi, ATP, glucose-6-phosphate, and UDPG was determined using in vivo(31)P nuclear magnetic resonance spectroscopy. Maize (Zea mays) root tips were perfused with a solution containing 0.5 or 1.0 millimolar phosphate at pH approximately 6.5 under different conditions. In the aerated state, phosphate uptake resulted in a significant increase (>80%) in vacuolar Pi, but cytoplasmic Pi only transiently increased by 10%. Under N(2), the cytoplasmic Pi increased approximately 150% which could be attributed to a large extent to the breakdown of ATP, sugar phosphates and UDPG. Vacuolar Pi increased but only to the extent of approximately 10% of that seen under aerobic conditions. 2-deoxyglucose pretreatment was utilized to decrease the level of cytoplasmic Pi. When pretreated with the 2-deoxyglucose, the excised maize roots absorbed phosphate from the perfusate with a significant increase in the cytoplasmic Pi. The increase could only be traced to external phosphate since the concentrations of other phosphorus containing species remained constant during the uptake period. With 2-deoxyglucose pretreatment, phosphate uptake under anaerobic conditions was substantially inhibited with only the vacuolar phosphate showing a slight increase. When roots were treated with carbonyl cyanide m-chlorophenyl hydrazone, no detectable Pi uptake was found. These results were used to propose a H(+)-ATPase related transport mechanism for phosphate uptake and compartmentation in corn root cells.
authors: U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Philadelphia, Pennsylvania 19118.
authors: S I
authors: SI
authors: Tu
authors: J R
authors: JR
authors: Cavanaugh
authors: R T
authors: RT
authors: Boswell