| Global average surface air temperature has increased about 0.74℃since 100 years ago, and will still increase about 1.8-4.0℃by the end of the 21st century (IPCC), meanwhile, according to the model predicted that average air temperature might will rise about 2.2-4.2℃by the end of the 21 century in China. At present, an experimental study on the responses of terrestrial ecosystems to warming mostly focus on the natural ecosystems, however, there are few studies on the responses and mechanisms of farmland ecosystems to different diurnal warming regimes. Since most previous researches on warming effects were based on crop modeling and historical data analyses, correlated with this experiment studies have been performed under controlled conditions, such as close greenhouses and open-top chambers with air condition facilities, but they are difficult to reflect crop actural responses at crop system scale in situ. Rice is the most important cereal crop of China, produced 40% of total grain yield. A study on the response characteristics and mechanisms and of yield and quality of rice to the different diurnal warming regimes under climate warming, and it plays a key role for people to enhance the understanding of relationship between global climate change and terrestrial ecosystems, and to reduce the uncertainties of modeling predicted for crop productivity and to ensure food security under climate change in future. Therefore, based on existing in field warming facilities in the world, we applied an experimental warming facility with three warming scenarios (AW:all-day warming; DW: daytime warming; NW:nighttime warming) using Free Air Temperature Increase (FATI) technique in 2006-2008 in Nanjing city, Jiangsu province, China. Our objectives were to (1) assess the practicability of the FATI system and effects of warming on rice growth, (2) investigate the effects of the different diurnal warming regimes on growth duration, aboveground biomass accumulation, yield and its component, grain filling, photosynthesis properties of rice plant, rice quality, the activities of carbon-nitrogen assimilation related key enzymes and antioxidant enzymes and lipid peroxidation in jianghuai region. The main conclusions are as follows: The free air temperature increased system formed 2 m×2 m of evenly and reliably warming area both at daytime and at nighttime. The daily mean temperature in the crop canopy of the different warming regimes about less than 2.0℃, and the diurnal trends of mean temperature change in the crop canopy during the whole growth duration under warming plots were all similar to those under control. Our field warming system under FATI facility can accord with the trends of future climate warming and is suitable to study the actual responses and adaptations of rice productivity to climate warming at system-level in situ in jianghuai region.Across the three-year experimental period, field warming tended to reduce the aboveground biomass by average 9.1%,10.3% and 3.3%, and the grain yield by 0.9%, 6.4% and 6.1% in the AW, DW, and NW plots, respectively. The decreasing trend of the grain yield was mainly attributed to the warming-led negative impacts on the filled grain number and the grain weight. Compared to the un-warmed, warming tended to decrease the panicle rate and the dry matter translocation rate (DMT rate). Meanwhile, field warming led to an obvious shortness of the initial heading date, while grain filling duration almost kept unchanged.The AW, DW and MW increased head rice rate by 14.2%,3.6% and 2.2% in 2007 and decreased significantly by 8.3%,5.7% and 5.5% in 2008, respectively. All the treatments increased significantly chalky grain rate and chalkiness of rice grain, and decreased the starch content and amylose content of rice grain during the two years. Field warming led to the reduction the ratio of amylopectin to amylose in 2007, while the increase significantly it by 4.6%,3.6% and 4.0% in the AW, DW and NW plots in 2008, respectively. There were increasing trends of peak viscosity, hot viscosity, break down and pasting temperature, and decreasing trends of final viscosity, setback and consistency in rice grain under the warmed plots. The content of grain protein was increased in 2007, while it was decreased in 2008 by warming treatments.Although warming treatments enhanced rice photosynthetic parameters, such as green leaves biomass rate and photosynthetic pigment of flag leaf, there were no impacts on leaf photosynthetic rate. Furthermore, warming stimulated leaf respiration rate at nighttime existed in the DW and NW plots which were 6.4% and 54.5% higher than those in the control plots, respectively. There were decreasing trends of photosynthetic system II (PS II) actual photochemical efficiency (ΦPSⅡ) and maximum photochemical efficiency (Fv/Fm), while increasing trends of leaf original fluorescence (Fo). Warming-induced a reduction of the maximum weight of a kernel,1000-grain weight, the time reaching the maximum grain rate and the time of grain filling reaching 99% of superior grain. Moreover, the activity of SS in superior grain decreased under the warmed plots during the early phase of rice grain filling, while had certain differences during the late phase of rice grain filling. The activity of ADPG-PPase in superior grain reduced under the warmed plots during the early phase of rice grain filling, while the activity of ADPG-PPase in inferior grain decreased under the warming plots during the early and middle phases of rice grain filling. Warming treatments enhanced the activities of SSS in superior and inferior grains, while had no significant effect on the activities of SBE in superior and inferior grains during the whole grain filling. The impact of SS and ADPG-PPase activity were greater on amylose content and that of SBE on amylopectin content in rice during the early phase of rice grain filling.The activities of GS and GOGAT in grain decreased under the warmed plots during the early phase of rice grain filling, while had certain differences during the late phase of rice grain filling. The protein synthesis was closely related to the activities of GS and GOGAT during the early phase of rice grain filling.The activity of superoxide dismatase (SOD) increased under the warmed plots, and AW, DW and NW enhanced the activity of SOD by 6.9%,5.4% and 19.1% on average during the whole grain filling. The activity of peroxidase (POD) increased in NW plot, while the activity of POD increased under the AW and DW plots during the early and late phases of rice grain filling, and it reduced during the middle phase of rice grain filling. The activity of catelase (CAT) increased under the AW and DW plots, while the activity of CAT elevated in NW plot during the early phase of rice grain filling, and it decreased during the late phase of rice grain filling. Warming treatments decreased the content of malondialdehyde (MDA), which were 12.7%,15.2% and 9.1% lower on average in the AW, DW and NW plots than the control during the whole grain filling, respectively.
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