Abstract: Drought stress is one of the major limitations to plant growth and development. To date, many studies have focused on network signaling pathways that regulate plant responses to drought. However, many of the principal signaling components and their interactions remain largely unknown. Guard cells, located in the epidermis of plant leaves, control both the influx of CO₂ and water loss during transpiration, and have become a highly developed system for dissecting early drought signal-transduction mechanisms in plants. So it has central effects on controlling of water balance or improving drought tolerance to retaining optimal aperture of stomata in plants. Recently, infrared thermal cameras have been used to monitor the subtle differences in leaf temperature in plants. We used this system to screen a droughtsensitive mutant, doi1, in Arabidopsis. This mutant showed cooler leaf temperature and faster water loss rate than did the wild type under drought stress. The mutant gene NCED3 in doi1 was cloned by the TAIL-PCR method, and RT-PCR was used to confirm the authenticity of the TAIL-PCR result.