Effect And Its Causes Of FACE On Yield Formation And Grain Quality In Wheat

This study was carried out in the exclusive platform for free-air CO₂ enrichment (FACE) in wheat-rice ecosystems in China (Wuxi, Jiangsu province). A Weak gluten wheat cultivar Ningmai-9 (T. aestivum L) was tested. The CO2 concentration in FACE treatment was 570 μmol-mol^-1, with 370 μmol-mol^-1 as ambient (CK). Nitrogen application rates were 125, 250 kg hm^-2 in 2001-2002, and 90, 180, 250 kg hm^-2 in 2002-2003, respectively. The main purpose of the experiment was to study the impact of the elevation of global atmospheric CO2 on wheat production. The main results were as follows:1. Compared with CK, the duration from sowing to heading, and from heading to maturity of shortened 1.3 and 1.3 days, respectively, and the whole growth duration shank 2.7 days in FACE treatment. Plant height in FACE treatment enhanced 0.8-6.2 percent, and significantly increased the length of ear and top two internodes.2. In two year's experiment, FACE treatment significantly affected wheat yield. Compared with CK, grain output in FACE treatment increased 24.6 percent. Interaction between FACE and N was significantly enhanced grain output. Ears per square meter, grain number per ear and 1000-grain-weight in FACE, average value of the data in 2001-2002 and 2002-2003, significantly increased 17.8, 2.9, and 4.8 percent, respectively. FACE treatment significantly increased maximum tiller and percentage of productive tiller, which made effective ear positively enhanced.3. Biomass accumulation in FACE treatment significantly increased 15.6-40.6 percent at different stages. The tendency and degree of effects of FACE on biomassaccumulation were different with growth period. FACE treatment had no significant effect on the biomass accumulation from early wintering stage to jointing stage and from heading to maturity stage. The biomass-accumulated form jointing to heading stage was increased significantly, which were the great action of leaf area index (LAI) and net assimilation rate (NAR). Compared with CK, FACE treatment significantly reduces the ratio of leaf dry matter to total biomass of wheat plant, positively increased the ratio of dry matter of stem and sheath to total biomass, and negatively decreased the ratio of ear dry matter to total biomass. FACE treatment had no apparent influence on economic coefficient.4. FACE treatment significantly reduced N content, and increased N uptake in wheat plant at different growth stages. FACE treatment on N uptake from early wintering stage to jointing stage and from jointing to heading stage was significantly increased, and effect of FACE on that from heading to maturity stage was decreased. The ratio of N accumulated in leaf to total N uptake by wheat plant at different growth stages significantly decreased in FACE treatment, and the ratio of N accumulated in stem and sheath to total N uptake was increased significantly. The ratio of N accumulated in ear to total N uptake had different tendency and degree, which was significantly reduced in heading stage and increased in 20 days after heading. FACE significantly increased N use efficiency for biomass production (NUEp) 5.5-10.2 percent at different stages, and enhanced N use efficiency for grain output (NUEg) and N harvest index (NFQ), compared with CK.5. Grain protein components, contents of dry and wet gluten, sedimentation value in FACE treatment significantly reduced 9.8, 15.3, 11.5 and 20.9 percent, respectively. Grain test weight, contents of starch, moisture and flour extraction rate was 1.3, 2.9, 0.6 and 1.1 percent higher, respectively.6. Compared with CK, wheat yield in FACE treatment was significantly correlated with ears per square meter, grain number per ear, the total biomass, dry matter accumulated before heading and from jointing to heading stage, sends out of soluble carbohydrates.