We present real time vanadate (V5+ ) uptake imaging in acowpea plant by positron emitting tracer imaging system (PETIS). Vanadium-48was produced by bombarding a Sc foil target with 50 MeV -particlesat Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) AVFcyclotron. Then 48 V was added to the culture solution to investigatethe V distribution in a cowpea plant. The real time uptake of the 48V was monitored by PETIS. We measured the distribution of 48Vin a whole plant after 3, 6 and 20 hours of V treatment by Bio-imaging AnalyzerSystem (BAS). After the 20 hour treatment, vanadate was detected at the up-groundpart of the plant. To know the effect of V uptake on plant activity, 18F-labeled water uptake was analyzed by PETIS. When a cowpea plantwas treated with V for 20 hours before 18 F-labeled water uptakeexperiment, the total amount of 18F-labeled water absorption wasdrastically decreased. Results suggest the inhibition of water uptake wasmainly caused by the vanadate already moved to the up-ground part of the plant.