Comparisons of the stomatal conductance and electron transport rate of three Japanese rice cultivars including Himenorin in Ehime Prefecture

Abstract

This study focused on stomatal conductance (gs) and electron transport rate (ETR) as one possible approach to the mechanisms of controlling canopy temperature and photosynthetic traits in rice. Three Japanese rice cultivars, Koshihikari (KH), Nikomaru (NM), and the new cultivar Himenorin (HR) developed in Ehime Prefecture were selected for the experiment. From the uppermost to the fifth leaves of five or more rice plants of each cultivar, gs and ETR were measured in situ using a handheld porometer/fluorometer. The results revealed the highest gs in HR among the three cultivars in all leaf positions from before the flag leaf extension until the maturity stage, which could be regarded as one of the advantageous mechanisms for moderating the thermal condition of the canopy with larger transpiration and supporting a higher photosynthetic level. The ETR of HR was highest among the three cultivars in most leaf positions from the heading stage to the maturity stage, which could be expected to maintain a higher photosynthetic level. These traits of gs and ETR in HR compared with NM and KH could be assessed as possible synergistic mechanisms for higher production and quality of rice with higher photosynthetic potential.