CARBON-DIOXIDE AND TEMPERATURE EFFECTS ON RICE (ORYZA-SATIVA L, CV IR-72)

The current increase in atmospheric carbon dioxide concentration ([CO2 ]) along with predictions of possible future increases in global air t emperatures have stimulated interest in the effects of [CO2] and tempe rature on the growth and yield of food crops. This study was conducted to determine the effects and possible interactions of elevated [CO2] and temperature on the development, growth and yield of rice (Oryza sa tiva L., cv. IR-72). Rice plants were grown season-long in outdoor, na turally sunlit, controlled-environment, plant growth chambers. Chamber air temperatures were controlled to follow a continuously and diurnal ly varying, near sine-wave control setpoint that operated between maxi mum (daytime) and minimum (nighttime) values. Day/night (maximum/minim um) air temperature treatments were: 32/23, 35/26, and 38/29-degrees-C . Dewpoint air temperatures were maintained at 18, 21, 24-degrees-C in the 32/23, 35/26, 38/29-degrees-C dry bulb air temperature treatment, respectively. Daytime [CO2] was controlled to 330 and 660 mumol CO2 m ol-1 air in each of the air temperature treatments. The time interval between appearance of successive mainstrem leaves during reproductive development was reduced by increasing air temperature treatment (P les s-than-or-equal-to 0.05) but was not affected by [CO2] enrichment. In this experiment [CO2] enrichment did not affect (P less-than-or-equal- to 0.10) grain yield, components of grain yield, final above ground bi omass or harvest index. Increasing temperature during growth, particul arly from the 35/26 to 38/29-degrees-C reduced grain yield, individual grain mass, and harvest index. The reduced grain yields with increasi ng temperature treatment suggest potential detrimental effects on rice production in some areas if air temperatures increase.