Effects of CO2 and Temperature on Rice

A Summary of Five Growing Seasons

抄録

Projected future climate change includes a strong likelihood of increased atmospheric carbon dioxide concentration ([CO2]) and possible increases in air temperatures. Since 1987, several [CO2] and temperature experiments have been conducted on rice (Oryza sativa, L., cv. IR-30) in outdoor, naturally-sunlit, environmentally controlled, plant growth chambers by USDA-ARS and the University of Florida, at Gainesville, Florida, USA. The objectives of this paper are to summarize some of the major findings of these experiments. Among these experiments, [CO2] ranged from 160 to 900μmol CO2 mol^-1 air while temperature treatments ranged from 25/18/21 to 40/33/37°C (daytime dry bulb air temperature/nighttime dry bulb air temperature/paddy water temperature). Total growth duration was shortened by 10 to 12 days across a [CO2] range from 160 to 500μmol mol^-1 due to a shortened vegetative phase of development and a reduction in the number of mainstem leaves formed prior to panicle initiation. Photosynthesis, growth, and final grain yield increased with [CO2] from 160 to 500μmol mol^-1 but were very similar from 500 to 900μmol mol^-1. Carbon dioxide enrichment from 330 to 660μmol mol^-1 increased grain yield mainly by increasing the number of panicles plant^-1 while increasing temperature treatment above 28/21/25°C resulted in decreased grain yield due largely to a decline in the number of filled grain panicle^-1. Evapotranspiration decreased and water-use efficiency increased with increasing [CO2] treatment while the reverse trends were found with increasing temperature treatment. These results indicate that future increases in [CO2] are likely to benefit rice production by increasing photosynthesis, growth, and grain yield while reducing water requirements. In warmer areas of the world, possible future increases in air temperature may result in yield decreases and increased water requirements.