Abstract

The projected doubling of current levels of atmospheric CO₂ concentration [CO₂] during the next century, along with increases in other radiatively active gasses, has led to predictions of increases in global air temperature and shifts in precipitation patterns. Since 1987, several [CO₂] and temperature experiments have been conducted by the University of Florida and USDA-ARS at Gainesville on rice (Oryza sativa L., cv. IR-30) in outdoor, naturally-sunlit, environmentally-controlled, plant growth chambers. The objectives of this chapter are to summarize some of the major findings of these experiments. In these experiments, season-long [CO₂] treatments ranged from 160 to 900 µmol 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/constant paddy water temperature). Total growth duration was shortened by 10 to 12 d as [CO₂] increased across a [CO₂] range from 160 to 500 µmol mol⁻, due mainly 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 500 µmol mol⁻¹, but were very similar from 500 to 900 µmol mol⁻¹. Carbon dioxide enrichment from 330 to 660 µmol mol⁻¹ increased grain yield mainly by increasing the number of panicles per plant, and increasing temperature treatment above 28/21/25°C resulted in decreased grain yield, due largely to a decline in the number of filled grain per panicle. 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 and reducing water requirements. In warmer areas of the world, possible future increases in air temperature may result in yield decreases and increased water requirements.

Copyright © 1995. . Copyright © 1995 by the American Society of Agronomy, Inc., 5585 Guilford Rd., Madison, WI 53711 USA