Screening of stomatal mutants in Arabidopsis using a novel controlled environmental infrared imaging system

Isolation and characterization of stomatal mutants is essential for a better understanding of the genetic and physiological underpinning of guard cell responses to environmental stimuli. A precisely controlled environmental chamber (PCEC) system specifically for screening stomatal mutants has been developed. The PCEC consists of several parts including plant chamber, environmental control unit and infrared camera. A window made of optical germanium with high transmittance to infrared light is embedded in the top of the plant chamber so that the surface temperature of plants can be accurately monitored by the infrared camera outside the chamber, while the environment can be stably maintained inside the sealed and double-glazed chamber. Using this novel PCEC system, we carried out a series of genetic screenings on a SALK T-DNA insertion population and identified some new stomatal mutants showing a reduced response to humidity, CO2 or temperature. Furthermore, we characterized a mutant with lower leaf thermal profile under low humidity and designated it as low humidity response1 (lhr1). The lhr1 mutant showed reduced sensitivity to external stimuli and increased transpirational water loss due to a defect in stomatal regulation. Our results suggest that this novel system can conveniently and accurately assess the impact of changing environmental conditions on stomatal behavior and facilitate the studies into the signal transduction pathways of guard cells.