Abstract: Difference in the competition between rice and barnyardgrass at different growth stages and generations under FACE (Freeair CO2 enrichment, 580 μmol/mol) conditions was studied in the field. Under the FACE conditions and a 12∶1 transplanting ratio for rice and barnyardgrass, the growth and photosynthesis of the second generation rice (FR2) declined at both tillering and heading stages compared to its parent (FR0). The dry weight of FR2 decreased by 18.8% and 61.9% respectively compared with FR0. And the net photosynthetic rate of FR2 decreased by 22.4% and 27.8%, respectively, compared with FR0 at the tillering and heading stages. On the other hand, the dry weight of barnyardgrass progeny (FB2) decreased by 345% and 31.0%, and the net photosynthetic rate of FB2 decreased by 28.4% and 16.3%, respectively, compared to its parent (FB0) at the tillering and heading stages. After longterm exposure to high CO2 concentration, the competition between rice and barnyardgrass had changed gradually as the time of exposure was prolonged. The FR2/FB2 ratio for biomass and net photosynthetic rate increased by 26.6% and 8.3% at the tillering stage, whereas decreased by 44.1% and 13.8% at the heading stage, respectively, compared to the FR0/FB0 ratio. It indicates that the competition between rice and barnyardgrass progeny had acclimated to an elevated atmospheric CO2 concentration at the later growth stages.

Key words: air carbon dioxide enrichment, rice, barnyardgrass, progeny, photosynthesis, competition

摘要： 通过田间试验,研究了开放式空气CO2浓度升高 (FACE，Freeair CO2 enrichment) 条件下不同生育期子代与0代水稻(Oryza sativa) 和稗草(Echinochloa crusgalli) 的生长和竞争关系。 结果表明, FACE 条件下水稻/稗草比例为12∶1 时, 在分蘖期和抽穗期，子代水稻和稗草的生长和光合能力比0代都有所降低，其中水稻的子代干物质量与0代相比分别降低了18.8%和61.9%，子代净光合速率则分别降低了22.4%和27.8 %；而稗草子代干物质量与为0代相比在分蘖期和抽穗期则分别下降了34.5%和31.0%，子代净光合速率也分别下降了28.4%和16.3%。FACE条件下，两代水稻与稗草的竞争能力（子代的稻稗比）都随着生长期的不同而发生了变化：稻稗干物质量比在分蘖期子代比0代增加了26.6%，而抽穗期则减少了44.1%；净光合速率稻稗比在分蘖期子代比0代增加了8.3%，抽穗期减少了13.8%，即FACE条件下子代水稻的竞争能力相比0代水稻在分蘖期有一定程度的增强，而在抽穗期却减弱。说明生长后期子代水稻/稗草的竞争已对FACE表现出一定的适应性。

关键词: 大气二氧化碳浓度增高, 水稻, 稗草, 子代, 光合作用, 竞争