Leaf gas exchange of upland and lowland rice cultivars

Abstract

Leaf gas exchange of upland and lowland rice cultivars were measured during late vegetative and during grain filling stages in the field under upland and lowland growth conditions. The rate of photosynthesis and water use efficiency (the rate of photosynthesis/the rate of transpiration) under upland conditions decreased with ageing, but generally varied little among four cultivars. At mid-grain filling under lowland conditions, upland cultivars showed lower rates of photosynthesis and transpiration than the lowland cultivars with concomitant reduction in whole plant conductance. At this stage, water use efficiency was higher under upland conditions than under lowland conditions, particularly in the upland cultivars. Water stress reduced the rate of photosynthesis without altering water use efficiency.

Potential rice yields in future weather conditions in different parts of Asia.

“…During the day, the C02 concentration in the stomatal cavity of rice tends to be a constant fraction of that in the ambient air. The photosynthetic rate of rice increases curvilinearly with the C02 concentration in the stomatal cavity (Dingkuhn, 1985;Fukai et al, 1985;Saitoh & Ishihara, 1987), whereas stomatal resistance and transpiration rate seem to be independent of C02 concentration (Akita, 1980;Dingkuhn, pers. comm.).…”