冬小麦品种对高浓度CO2差异响应的机理研究

It has been reported that wheat cultivars respond differently to elevated CO2 concentrations ([CO2]). Therefore, selecting cultivars with higher grain yield responsiveness to elevated [CO2] is crucial to global food security and adaption to climate change. Our previous study showed a down-regulation of photosynthesis after anthesis, when wheat plants were exposed to elevated [CO2] in the long term. Such acclamatory response may be attributed to the accumulation of carbon (C) assimilate in the leaves and reduction in leaf nitrogen (N) content. The partitioning of the carbohydrates and C sink strength may limit C assimilation rate and yield response to long-term exposure to elevated [CO2]. Sucrose-phosphate synthase (SPS) is a regulatory enzyme involved in the partitioning of photoassimilates between sucrose and starch. In the proposed study, field experiments will be conducted at the Free-air CO2 Enrichment (FACE) facility in Beijing, China. Three wheat cultivars with different spike type are selected. The objectives of this study are to determine the intraspecific variation of wheat in (i) the response to elevated [CO2] with respect to the sink strength of the cultivars; (ii) the C and N metabolism of the flag leaf, dynamics of grain starch accumulation and grain filling process; and (iii) the partitioning of photoassimilates and N uptake under elevated [CO2] among the selected cultivars. Through revealing the physiological and biochemical mechanism of contrasting cultivars in response to elevated [CO2], this study will provide critical information on crop selection and adaptation to climate change.

冬小麦产量对CO2浓度升高的响应存在品种差异，筛选CO2高响应品种对保障未来粮食安全和适应气候变化具有重要意义。本人前期研究表明冬小麦长期暴露在高CO2浓度条件下，特别是开花后表现为光合下调，这与叶片碳同化物的积累和氮含量降低有关。因此，在高CO2浓度下，作物长期保持较高的碳同化水平，进而表现出较高的增产幅度，可能受到碳同化物分配和库容强度限制。蔗糖磷酸合成酶（SPS）在光合产物的分配中发挥重要作用。本研究依托开放式CO2浓度升高试验（FACE）平台，以不同穗型冬小麦为研究对象，定量评估品种间的CO2肥效差异，揭示籽粒库容大小与CO2肥效之间的关系；对生育后期旗叶碳氮代谢、籽粒淀粉积累动态及籽粒灌浆进程进行比较分析；探讨高浓度CO2下不同穗型小麦品种能否在开花后保障碳同化物分配、增加氮吸收，从而协调碳氮代谢，揭示冬小麦高、低响应品种的生理生化机制，为筛选适应气候变化的种质资源提供理论依据。

本课题针对全球变化CO2浓度升高对农业适应措施的需求，基于不同类型品种对CO2浓度升高的响应的定量评估，揭示品种间对CO2浓度升高差异响应的生理和分子机制。课题组对研究内容进行了实施部署和具体落实，完成了课题研究工作并取得了重要进展。CO2浓度升高条件下，大穗型品种的产量增幅（16.7%）高于中间型（9.4%）和多穗型（9.7%），主要增加了单位面积穗数（6.16%）和穗粒数（4.08%）。发挥非叶绿色器官的光合耐逆机能，扩大碳素利用率，同步提高小麦对CO2升高的响应，突破了传统的栽培理念（强调叶片作用，大水大肥促叶片），提出扩大库容量是适应CO2浓度升高的重要手段；揭示不同品种的光合生产特征、物质积累与时空分配特征、碳氮代谢与源库性能特征与产量形成特征，阐明大穗型品种会采用库转移的方式来适应，通过将叶片中多余的淀粉、蔗糖转移到茎鞘中暂存，缓解叶片的压力，提高碳素的利用率；从光合碳固定、电子传递到碳代谢产物的运转途径入手，剖析冬小麦品种在CO2浓度升高条件下的丰产性优势性状形成的主控过程和影响因素，CO2浓度升高使拔节期NL10，SH8675，ZYM和SLM的Ag,max分别升高22.3%，33.1%，34.4%和21.4%(P<0.05)。而进入开花期后，CO2浓度升高仅对SH8675的Ag,max起到显著促进作用，增幅达到了43.2%(P<0.05)，对其他品种没有显著影响，揭示大穗型品种生殖生长阶段的电子传递过程对CO2浓度升高响应的重要作用；发现了冬小麦品种间CO2高效利用的基因差异，小麦叶片中与类囊体和光合作用有关的功能基因，在高CO2浓度条件下上调表达，经过RT-PCR证实，提出CO2高效品种的关键代谢途径，氧化磷酸化等途径。通过项目的实施，课题组在北京建立野外田间试验基地，发表论文9篇，其中SCI论文4篇，培养高级职称晋升2名，博士后1名，研究生1名，国际国内会议报告10余人次。