| Atmospheric CO2 enrichment and temperature increasing are two main characteristics of global climate change. CO2 concentration and temperature are two important environmental factors that affect crop growth and development. Determining the effects of free air CO2 enrichment and increased temperature on rice yield formation and dry matter partitioning is the precondition of precisely estimating the impacts of global climate change on food security. Rice is one of the three major food crops in China and also in the world, rice yield directly impacts food security in China. Dry matter partitioning and yield components are important aspects of yield formation and directly influence crop yield. In order to determine the effects of free air CO2 enrichment and increased temperature on rice yield formation and dry matter partitioning, experiments on rice (Oryza sativa L.) cultivar ’Changyou 5’were conducted from May 2012 to October 2013 in the first experimental platform of Free Air CO2 Enrichment And Increased Temperature (TFACE) in China, located at Changshu, Jiangsu province. There were 4 treatments in the experiments, which included control, free air CO2 enrichment (550ppm), increased temperature (+2℃) and combining of free air CO2 enrichment and increased temperature (550ppm,+2℃). Effects of free air CO2 enrichment and increased temperature on rice yield, rice yield components (Panicles per square meter, Spikelet number per panicle, seed setting rate,1000-grain weight) and dry matter partitioning were studied according to the experimental data. The main results are listed below:(1) Impacts on rice yield:Rice yield under FACE treatment increased 545 kg/hm2, the increase ratio compared to control was 6.3%, and difference was significant. Rice yield under T treatment decreased 2335 kg/hm2, and the decrease ratio compared to control was 27.0%. The differences of rice yield between T and control reached the extreme significant level. Rice yield under F+T treatment decreased 1630kg/hm2, and the decrease ratio compared to control was 18.8% respectively. FACE and T had no significant interaction effects on rice yield.(2) Impacts on rice yield components:Rice panicles per square meter increased 5.7% and 7.1%, respectively, under FACE treatment and F+T treatment, and decreased 2.0% under T treatment. Rice spikelet number per panicle increased 10.2% under FACE treatment, and reduced 37.5% and 23.9%, respectively, under T treatment and F+T treatment. Rice seed setting propagation coefficient reduced 5.3%,10.1%, and 10.8%, respectively, under FACE treatment, T treatment and F+T treatment.1000-grain weight under FACE treatment increased 3.9%, and decreased 3.8%, and 6.6%, respectively, under T treatment and F+T treatment. Interaction impacts of FACE and T on rice spikelet number per panicle and seed setting propagation coefficient were not significant, while the interaction effect of FACE and T on panicles per square meter and 1000-grain weight reached a significant level. Increased rice yield under FACE treatment is mainly due to the increased Spikes and increased spikelet number per panicle. Combining CO2 concentration enrichment and increased temperature had the greatest influence on the spikelet number per panicle (reduced 22.9%). Panicles per square meter increased slightly (7.1%), but this increase was not enough to compensate the negative effect on yield caused by the reduction of spikelet number per panicle.(3) Leaf, stem and ear dry weights were increased under FACE treatment, while decreased under T treatment. The impacts of F+T on leaf and stem dry weight were not significant, but the ear dry weight in seed filling period and seed maturation stage were decreased. The effects of FACE on partitioning index of leaf, stem and ear in each developmental stage were not significant. Partitioning index of leaf in each developmental stage and partitioning index of stem in the maturation stage were increased under T treatment; the partitioning index of ear in the maturation stage was significantly decreased, and the partitioning indices of ear and stem in other developmental stages were not affected. Effects of F+T on partitioning index of leaf in each developmental stage and partitioning indices of stem and ear in elongation stage and heading stage were not significant; partitioning indices of stem in seed filling stage and maturation stage were increased, while partitioning indices of ear in seed filling stage and maturation stage were decreased.This study showed that the positive effect of elevated CO2 with 123ppm couldn’t offset the negative effect of increased temperature with 1.4℃ and resulted in yield loss by 18.8%. Our study results can facilitate further quantitatively study of the impacts of global climate change on rice production, and can assist the improvement of rice cultivation management so as to cope with the impacts of global climate change on rice yield. |
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