| Rice is one of the staple crops in P.R. China, grain output of rice occupies over 40 percent of total food production. Faced with the continuous increase in the concentration of atmospheric CO2, the following questions need to be addressed: How does this change influence rice growth and yield formation in rice? And, what measures can be taken to cope with the effect of the atmospheric CO2 elevation on rice production? Free-Air CO2 Enrichment (FACE) is designed to elevate CO2 concentration under field condition. Carbon dioxide concentration is computer-controlled so that plants growing within the FACE rings are supplied with air with the desired CO2 concentration and their growth condition, both above and underground, is well consistent with natural environment. Therefore, it is generally agreed that FACE approach is the most realistic of the techniques currently employed to create higher concentrations of atmospheric CO2 in order to study the impacts of CO2-enriched air on plant growth and development. The present study was carried out in the culture chest and the FACE platform, using Asominori (Japonica) and IR24 (Indica) rice cultivars. The CO2 concentration in the culture chest was 700μmolmol-1 treatment) and 380μmol·mol-1(CK), the CO2 concentration in the FACE treatment was 570 μ mol·mol-1, with 370μ mol·mol-1 as ambient (CK). The objectives were to study the effects of high CO2 concentration on rice growth of seedlings, yield and its components, biomass production and distribution, plant height and its components, QTL analysis for plant height and its components under FACE, it will be useful for developing new rice cultivars to adapt to the continuous increase in the concentration of atmospheric CO2. The main results were:1. Germination percentage and the activities of amylase in Asominori and IR24 had no change under two CO2 concentration. Plant height, dry matter weight, stem thickness, the vitality of seedling roots increased under the high CO2 concentration, in contrast, the root length and the ratios of root and shoot (R/S) decreased. The chlorophyll content and optimal/maximal photochemical efficiency of PS II had no change. Under high CO2 concentration, the length of leaf increased, the length of long cell and short cell in Asominori increased (P. 0.01) the length of short cell in IR24 increased (P. 0.05) either.2. Yield and its correlated traits in Asominori and IR24, namely yield per pant, fertile tillers, panicle length, primary branches, grain number per panicle, seed setting rate, 1000-grain weight and seed setting, were greater under FACE than those under CK. The increased ranges were: 23.46% and 33.21% in yield per plant; 10.58% and 5.35% in fertile tillers; 1.88% and 9.00% in panicle length; 2.85% and 7.01% in primary branches; 6.05% and 19.57% in grain number per panicle; 3.38% and 19.00% in seed setting rate; 6.12% and 5.88% in 1000-grain weight; 0.63%和 3.22% in seed setting. The number of stem and tiller in different growing stage was higher than CK, tillering speed was higher than CK, however, the percentage of productive tiller decreased (P. 0.05); there was a positive coefficient of correlation between yield per plant and fertile tillers per plant (P. 0.01); path coefficient analysis showed that in contribution to grain yield, fertile tillers per plant come first, the grain number per panicle second.3. FACE treatment increased the dry matter accumulation in main stem and the constituent components of Asominori and IR24 during heading stage to maturity stage, ranging from 4.85%36.66% and 14.75%40.76% respectively. FACE treatment increased the leaf area index (LAI) of Asominori and IR24; the increased rate were 29.32% and 18.52% in heading stage, 2.56% and 34.13% in maturity stages. The net assimilation rate (NAR) was also higher under FACE from heading stage to maturity stage, the increased rate were 13.20% and 39.93% respectively. The increased LAI and NAR were the main reason of higher dry matter accumulation under FACE. The dry weight per day...
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