依托中国稻田臭氧FACE（Free Air ozone Concentration Enrichment）技术平台，以常规籼稻扬稻6号为供试材料，设置大气臭氧浓度（Ambient）和高臭氧浓度（比Ambient高50%），移栽密度设置低密度（16穴/m2）、中密度（24穴/m2）和高密
收稿日期: 20131114； 修改稿收到日期: 20131223。
基金项目: 国家自然科学基金资助项目（31371563，31071359和30871486）；江苏省普通高校研究生科研创新计划资助项目（CXZZ11_0984）；土壤与农业可持续发展国家重点实验室开放基金资助项目（0812201233）；中国科学院知识创新方向项目（KZCX2EW414）； 中国科学院科研装备研制项目（YZ0603）； 江苏省作物栽培生理重点实验室开放课题资助项目（K12006）；扬州大学科技创新培育基金资助项目（2012CXJ054）。
度（32穴/m2），研究不同移栽密度下近地层臭氧浓度升高对水稻生长发育和产量的影响。结果表明,高浓度臭氧对水稻抽穗期、成熟期和最终株高均无显著影响，但使收获期生物产量显著下降，其中低、中和高密度条件下分别下降23%、20%和9%。臭氧胁迫导致的生物产量下降主要与拔节至抽穗期物质生产量明显下降有关（-23%），而营养生长期物质生产量差异不显著。前者主要与高浓度臭氧下水稻生长后期的净同化率（NAR）显著下降有关，也与该期叶面积指数（LAI）下降部分相关。高浓度臭氧对营养生长期不同器官生物量影响较小，但可使生殖生长期各器官生物量显著下降，其中茎鞘生物量降幅大于叶片，因此，臭氧胁迫下生物量在叶片中的分配比例呈增加趋势，而在茎鞘中的分配比例则相反。臭氧胁迫对单位面积穗数和每穗颖花数均无显著影响，但使饱粒率和饱粒重显著下降，空粒率和秕粒率明显增加。臭氧胁迫使水稻籽粒产量平均下降16%，其中，低、中、高密度下分别下降24%、14%和10%。臭氧胁迫对水稻生长后期的LAI、NAR、物质生产量以及每穗颖花数、饱粒重和籽粒产量的负面影响均随密度的增加而呈减小的趋势。以上结果表明，适当增加移栽密度可以减小臭氧胁迫对水稻生长后期的光合面积特别是净同化率的影响，进而减轻对颖花分化和籽粒生长过程的伤害，最终可显著减少臭氧胁迫下经济产量的损失。
In order to investigate the effects of ozone stress on growth, development, yield formation of rice, we conducted a free air ozone concentration enrichment (FACE) experiment. A conventional indica rice cultivar Yangdao 6 was grown in the field at ambient and elevated ozone concentrations (ambient×1.5) with 3 spacing levels: low planting density (LD, 16 hills/m2), medium (MD, 24 hills/m2) and high planting density (HD, 32 hills/m2) . The results were as follows: elevated ozone had no impact on heading stage, maturity stage and final plant height, but significantly reduced biological yield by 23%, 20% and 9% under LD, MD and HD, respectively. The ozoneinduced decrease in biological yield was mainly due to the decrease in dry matter production during jointingmaturity stage (-23%), while dry matter production before jointing stage was remained unaffected. The former was mainly due to the significant decrease in net assimilation rate (NAR), and partly due to the reduction in leaf area index (LAI) in the later growth stage. The biomass of plant tissues under elevated ozone was not affected at the vegetative stage, but significantly reduced at the reproductive stage, with larger decline in stem biomass than in leaf biomass. As a result, green leaf biomass ratio increased, while the faction of stem showed an opposite trend. Ozone stress had no effect on the panicle number per unit area and spikelet number per panicle, but significantly decreased filled grain percentage and filled grain weight, thus increased the blighted grain rate and empty grain rate. Across the three planting densities, grain yield reduced significantly by 16% due to ozone stress, with the average reduction of 24%, 14% and 10% under LD, MD, and HD, respectively. With rising planting density the negative effects of ozone stress showed decreasing trends on LAI, NAR and dry matter production in late season, as well as spikelet number per panicle, filled grain weight and grain yield. The above results indicated that appropriate increase in planting density could reduce ozone damage to LAI, especially to NAR in the late growing stage, thus on the processes of spikelet formation and grain growth, and finally decreased ozoneinduced yield loss.
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