Development of a Simple and Rapid Measurement System for Determining CO₂ Assimilation Rate in Plant Leaves

Field measurement of CO₂ assimilation rate in plant leaves is done by clumping the leaf with a chamber and waiting a few minutes for each measurement using special carry on equipment. This costly and labor-intensive method has hindered the acquisition of large-scale data on photosynthesis of field grown plants. We created MIC-100, a new closed-type photosynthesis measurement device with a novel infrared gas analyzer cell that enables high-throughput measurement of leaf CO₂ assimilation rate. The measurement time required for a single leaf using MIC-100 was reduced to one-seventh that of conventional open system devices, while similar values were obtained for the same leaf under high-light conditions. We also created two supporting technologies to obtain rapid photosynthesis measurements for field-grown rice: the upper-limb assist suit and the leaf area measurement system with a commercial document scanner. These systems enabled large-scale surveys of the natural genetic variation and ontogenetic changes among diverse sets of rice accessions. MIC-100 and the related systems will be useful for physiological studies with many other plant species and for growth surveys in the agricultural fields.