An AOTF (Acousto-Optic Tunable Filter)-based spectral imager was developed for hyperspectral measurement of plant reflectance in the field. A hyperspectral image cube for the spectral region between 450-900 nm could be acquired at 3 to 5 nm resolution intervals within a few seconds. The system was light and compact, and both the spectral wavelengths and intervals were programmable with PC control. Wavelengths could be tuned rapidly, either sequentially or randomly. The hyperspectral image cube for rice canopies obtained by the system showed its potential in the estimation of leaf nitrogen and chlorophyll concentrations. The AOTF-based hyperspectral system would have great potential for further investigations in remote sensing of biochemical and ecophysiological plant variables.