Abstract: Effect of Free-Air CO₂ Enrichment (FACE), 200μmol·mol^-1 CO₂ elevation under field condition, on the number of differentiated, retrograded, and survived primary and secondary branches and their spikelets in rice was investigated, and the percentage of retrograded branches and spikelets under FACEtreatment were also calculated. Results showed that the number of differentiated primary and secondary branches, the number and percentage of retrograded primary branches per panicle were not significantly affected by FACE, but the number and percentage of retrograded secondary branches per panicle significantly increased under FACEtreatment, which resulted in the significant decrease of survived secondary banches. FACEhad no significant effect on the number of differentiated, retrograded and survived spikelets on the primary branches per panicle. The number of differentiated spikelets on secondary branches per panicle was not significantly affected by FACE, but FACEtreatment significantly increased the number and percentage of retrograded spikelets on the secondary branches per panicle. Significant decrease of survived spikelets per panicle under FACEtreatment was chiefly caused by marked increase of retrograded spikelets on the secondary branches of survived primary branches. FACEtreatment significantly increased the surviving percentage of spikelets on the primary branches per panicle, while that on the secondary branches significantly decreased under FACEtreatment.

Key words: broadleaf plant, specific leaf area., leaf dry mass, leaf width, leaf area, leaf length