Abstract:

In order to clarify the competition for growth space between barnyard grass and rice under elevated atmospheric CO₂ concentration, the experiment on the Free-air CO₂ enrichment system (FACE) was conducted, taking barnyard grass ‘Jijing 88’ as the research object. The experiment included 4 treatments: rice-planting with atmospheric CO₂ concentration (CK), rice and barnyard grass with atmospheric CO₂ concentration (TB), rice-planting with high concentration CO₂ (550 µmol∙mol^-1) (TC), and rice and barnyard grass with high concentration CO₂ (BC). Morphology and physiological indexes of rice were measured and analyzed at each developmental stage of rice. The results showed that barnyard grass had a negative impact on the number of spikes per point and seed setting rate, but they had no significant effect on rice yield. Barnyard grass reduced plant height at the jointing stage, tiller number at heading stage and leaf area index at each growth stage of rice. The interaction of elevated atmospheric CO₂ concentration with barnyard grass significantly reduced the leaf area index of rice at the tillering stage and jointing stages. At the tillering stage of rice, the negative effect of barnyard grass on the oxidative capacity of rice roots was greater than the positive effect of high concentration of CO₂; at the jointing stage of rice, the interaction between elevated atmospheric CO₂ concentration and barnyard grass significantly reduced the active absorption area of rice roots. The higher concentration of CO₂ and barnyard grass had a great effect on the total absorption area of rice roots. The results indicated that, under the condition of elevated atmospheric CO₂ concentration, barnyard grass still has an obvious inhibitory effect on the growth space obtained by rice at tillering and jointing stages, which are also the key periods for the growth competition between barnyard grass and rice.

Key words: carbon dioxide (CO₂), barnyard grass, rice, climate change, free-air CO₂ enrichment system (FACE)

摘要：

为明确CO₂浓度升高条件下稗草（Echinochloa crusgalli）与水稻（Oryza sativa）生长空间的竞争关系,以“吉粳88”为研究对象,利用开放式CO₂富集系统（Free-air CO₂ enrichment,FACE）,开展了水稻与稗草共生混种试验。试验设置2个处理,CO₂摩尔分数分别为400 µmol∙mol^-1（自然大气情景下）和550 µmol∙mol^-1（高浓度CO₂环境应用FACE系统进行调控）。每个CO₂浓度处理中设2个稗草密度,分别为水稻清种和水稻与稗草混种,共计4个组合。以自然大气CO₂浓度下水稻清种处理为对照（CK）,自然大气CO₂浓度下水稻与稗草混种处理为TB、高浓度CO₂下水稻清种处理为TC、高浓度CO₂下水稻与稗草混种为BC。在水稻各发育期分别测定形态生理指标和根系指标并进行分析。结果表明,稗草混种处理对水稻每穴穗数和结实率均有负向作用,但未达到显著水平。稗草对水稻拔节期的株高有负向作用,稗草混种处理对水稻分蘖期叶面积指数下降了23.2%,使水稻在抽穗期分蘖数减少了34.5%,均达到显著水平。稗草混种处理降低了水稻根系氧化力,在水稻分蘖期、拔节期、抽穗期分别降低了41.6%、10.9%、14.2%,且均达到显著水平。稗草混种处理对水稻根系总吸收面积有负向作用,且在抽穗期和成熟期达到显著水平,在分蘖期达到极显著水平,CO₂浓度升高与稗草互作对水稻根系总吸收面积影响以负效应为主。研究结果明确了在CO₂浓度升高的条件下,稗草对水稻分蘖期和拔节期生长空间表现出明显的抑制作用,也是稗草与水稻生长竞争的关键时期。

关键词: 二氧化碳, 稗草, 水稻, 气候变化, 开放式CO₂浓度富集系统