[Effect of free-air CO2 enrichment (FACE) on spikelets differentiation and retrogression in rice (Oryza sativa)]

Effect of Free-Air CO2 Enrichment (FACE), 200 mumol.mol-1CO2 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 FACE treatment 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 FACE treatment, which resulted in the significant decrease of survived secondary banches. FACE had 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 FACE treatment significantly increased the number and percentage of retrograded spikelets on the secondary branches per panicle. Significant decrease of survived spikelets per panicle under FACE treatment was chiefly caused by marked increase of retrograded spikelets on the secondary branches of survived primary branches. FACE treatment significantly increased the surviving percentage of spikelets on the primary branches per panicle, while that on the secondary branches significantly decreased under FACE treatment.