| The unique Free-air CO2 Enrichment (FACE) experiment in China was conducted at Wuxi (latitude 31°37'N, longitude 120°28'E) in a rice paddy field. A Japonica cultivar (Wuxiangging 14) was used as tested rice cultivar. The CO2 concentration in FACE treatment was 570μmol ·mol-1.with 370μmol · mol-1 as ambient(CK). Nitrogen application rates were 150, 250 kg N ha"1 in 2001 and 150, 250. 350 kg N ha-1 in 2002 and 2003. respectively. The objective of the present study was to elucidate the effects of FACE on the grain quality of rice and its cause under different N application.1. Compared with ambient, FACE significantly increased the brown rice rate, the yield of brown rice and the yield of milled rice, but significantly reduced the milled rice rate, head rice rate and the yield of head rice. The brown rice rate, the milled rice rate and lead rice rate increased significantly with higher N supply. Suitable rate of N application ( 250 kg · ha-1) improved the yields of brown rice, the yield of milled rice and head rice significantly.2. Compared with ambient, FACE significantly increased the percentage of chalky grain and chalkiness degree, but had no impact on chalkiness area. Suitable rate of N application (250 kg·ha-1) significantly reduced the percentage of chalky grain, however, lower N application decreased the chaikiness area.3. Compared with ambient, FACE significantly increased the gelatinization temperature and significantly reduced amylose content, while gel consistency showed no change. Suitable rate of N application decreased gelatinization temperature and amylose content.4. Compared with ambient, FACE cause significant decreases in grain protein and Cu content, while had no impact on Zn and Fe content. Higher amount of N applicationresulted in significant increase in grain protein content, however, Fe contents showed the reverse.5. Compared with ambient, FACE significantly increased the peak visocisity of rice starch by 12.25RVU, hot viscosity by 8.94RVU, cool viscosity by 5.20RVU, leading to the increase in breakdown viscosity by 3.31RVU, the decrease in setback viscosity by 7.05RVU. As the rice starch with large breakdown viscosity and low setback viscosity generally has a better taste quality, it is therefore likely that the taste quality perhaps was improved with FACE. Lower N application(150 kg ·ha-1 )decreased peak viscosity, hot viscosity and cool viscosity significantly.6. Under FACE conditions, leaf-cutting had no significant effect on the brown rice rate, meanwhile significantly increased the milled rice rate, also significantly increased the head rice rate only under the medium N treatment and had no influence on the head rice rate under lower N treatment. On the other hand, spike-cutting for decreasing biomass pool in FACE significantly reduced the brown rice rate without affects on the milled rice rate, meanwhile significantly decreased the head rice rate just under lower N application compared to no significant effect under mediuml N treatment.7. Under FACE conditions, leaf-cutting had no effect on the percentage of chalky grain, chalkiness area and chalkiness degree. On the other hand, spike-cutting significantly reduced the percentage of chalky grain, chalkiness area and chalkiness degree with a larger percentage under medium N treatment than under low N treatment.8. Under FACE conditions, leaf-cutting decreased the gel consistency of rice and increased the gelatinization temperature with a larger percentage under medium N treatment than under low N treatment. Leaf-cutting and spike-cutting in FACE had no significant influence on the rice amylose content, however the protein contents significantly increased under both conditions.9. Higher increment of grain weight at early filling stage of rice resulted form lower milled rice rate, head rice rate and the protein content and higher percentage of chalky grain. At the late filling stage, the lower increment of grain caused lower milled rice rate and head rice rate, however, higher percentage of chalky grain, chalkiness...
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