9310850 Roberts The rates of malate metabolism and transport in maize root tips will be measured using nuclear magnetic resonance spectroscopy in combination with other biochemical techniques. These processes will be quantitated in tissue exhibiting different rates of malate synthesis, in response to potassium ion uptake, or assimilation of ammonium ion. Specific reactions that will be monitored include (i) utilization of glycolytically-derived malate by mitochondria for oxidation; (ii) action of PEP carboxylase and malic enzyme, and their coordination with activity in the Krebs cycle and amino acid biosynthesis; (iii) movement of malate between cytoplasm and vacuole. The combined measurements will permit observation of interactions between the different components comprising malate metabolism. This information is a prerequisite to an understanding of respiration, mineral nutrition, intracellular pH regulation, amino acid biosynthesis and growth - particularly with respect to the integration of these processes in vivo. ***
