高CO2浓度下黄瓜光合作用的钾调控机理研究

Some extensive and in-depth researches about the mechanisms of palnt photosynthetic acclimation to high CO2 concentration are reported in the condition of free-air CO2 enrichment (FACE). The key mechanism reported are about the feedback inhibition by photosynthesis product accumulation and stomatal limitation. However few study of photosynthetic acclimation and its mechanism are carried out under green house condition with CO2 fertilization and K supply as a stimulator. We would use cucumber (Cucumis sativus L. cv.) as research material. The aims of this study are: (1) To understand the effect of different K levels on accumulation and distribution of cucumber photosynthesis product in the leaves, stems, and roots under the condition of long-term higher CO2 concentration application (several weeks or several monthes); (2) To analysis the relationship between photosynthetic acclimation and stomatal limitation under K supply and long-term higher CO2 concentration application; (3) To analysis of the photosynthetic acclimation mechanism of cucumber under K supply and long term higher CO2 concentration application. The research would provide the theoretical foundation for sustainable production of cucumber in green house and benefit to reveal photosynthetic acclimation mechanism for green house vegetables and FACE conditions crops.

关于植物对CO2浓度增高的光合适应机理，在开放式CO2浓度增加（FACE）条件下已得到了广泛深入的研究。其机理重点围绕在光合产物超累积的反馈抑制与气孔限制等方面。然而人们很少关注设施蔬菜CO2施肥下光合适应的发生及其机理的研究，或通过钾素供应强度的刺激来揭示机理也鲜有报道。本项目以黄瓜为研究材料，利用开顶式气候培养室的盆栽试验，通过14 C示踪、光合作用测定、HPLC定性定量分析等方法研究钾素供应强度对黄瓜光合适应的调控机理。主要进行以下研究：（1）钾素供应强度对长期CO2浓度增高条件下黄瓜同化产物在源、流、库中积累及分配的调节；（2）钾素供应强度对长期CO2浓度增高条件下黄瓜气孔状态的调节与光合适应的关系；（3）钾素供应强度对长期CO2浓度增高条件下黄瓜光合适应的调控机理分析。本项目的研究对设施黄瓜栽培的可持续生产提供理论基础,有助于设施蔬菜及FACE条件下作物光合适应机理的深入开展。

为探究长期CO2加富(1000μmol/mol)条件下，黄瓜光合特征、光合产物分配、气孔状态对钾素水平的响应，本项目利用开顶式气室内的2次盆栽和3次水培试验，通过13C示踪、光合作用测定、HPLC定性定量分析等方法研究了K素供应强度对黄瓜光合适应的调控机理。主要得到以下结论：CO2加富会使黄瓜生物量显著增加，最大可增加111.3%；短时期（3周内）CO2加富会使黄瓜光合作用显著增强，但在24-30天（第四周末）会出现光合适应，其光合速率会降至自然CO2浓度以下；增加K素供应水平可以缓解黄瓜光合适应，即光合速率的降低会得到缓解，但很难恢复到自然CO2浓度下的光合作用。光合适应发生后没有发现K素水平能够缓解光响应曲线与CO2响应曲线由来的光合参数降低的迹象，对荧光参数也无显著影响。黄瓜在CO2加富条件下光合适应的发生，伴随有气孔限制，增加K素水平可缓解净光合速率与气孔导度的降低，即缓解黄瓜光合适应；由13C同位素示踪试验得到，在CO2加富条件下，增加K素水平光合同化C（δ13C）丰度的库（根）/源（叶）比始终大于正常钾素水平处理（0.14-0.15与0.025-0.032），这说明了增加K素水平促进了黄瓜光合产物由源向库的分配；可溶性糖与淀粉在叶片的异常累积（相比自然CO2浓度一下累积2.5倍）是CO2加富条件下黄瓜光合适应的主要原因，通过增加K素水平，可显著促进其向库的分配，进而缓解黄瓜光合适应。