外源钙介导气孔调控樟子松水分利用效率的生理机制研究

Pinus sylvestris var. mongolica is one of the main tree species used for forestation and grows well in the early growth stage on sandy lands in the semi-arid area of western Liaoning province. In recent years, many of trees of Pinus sylvestris var. mongolica plantations have been found to be degraded. Many research showed that water stress was one of the main reasons causing Pinus sylvestris var. mongolica plantation decline. We supposed that exogenous calcium can improve the ability of water stress resistance on Pinus sylvestris var. mongolica by two ways, that were, enhancing the activity of antioxidative enzyme system or increasing the ability of water use efficiency, based on stomatal movement of Pinus sylvestris var. mongolica needles including opening (or irregular closure) and closure conditions under different degree of water stress. Different concentration of exogenous calcium was used to deal with Pinus sylvestris var. mongolica seedlings under different water stress, explaining scientifically the influence of calcium on the water use efficiency (WUE) of Pinus sylvestris var. mongolica. Under greenhouse conditions, the influence of exogenous calcium on Pinus sylvestris var. mongolica was analyzed depending on the parameters included the hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents and the activities of catalase (CAT), superoxide dismutase (SOD), plasma membrane H+-ATPase and Ca2+-ATPase; The stomatal movement, net photosynthesis (A), transpiration (E), stomatal conductance (gs), intercellular CO2 concentration (Ci), Rubisco activity and content and WUE of Pinus sylvestris var. mongolica needles were measured with LiCor-6400 Photosynthesis System, demonstrating the influence of stomatal movement on photosynthetic characteristics and the effect of exogenous calcium on stomatal movement of needles of Pinus sylvestris var. mongolica under different water stress. Synthesized all of these parameters, the physiological mechanisms of exogenous calcium on WUE of Pinus sylvestris var. mongolica needles were studied, providing theoretical basis for the impacts of calcium on Pinus sylvestris var. mongolica under water stress.

樟子松人工林是辽宁省西部半干旱地区生态环境安全的重要屏障，具有防风固沙、保持水土等生态功能，近年出现大面积衰退现象。前人研究表明水分胁迫是引起樟子松人工林衰退的主要原因之一。本项目利用不同程度水分胁迫下樟子松针叶气孔运动可能存在的两种状态，即非闭合（或不均匀闭合）和闭合状态，假设两种气孔状态分别对应外源钙增强植物抗水分胁迫能力的两种途径，即提高抗氧化酶系活性和增强水分调控能力，研究外源钙对樟子松针叶水分利用效率的调控机制：①通过测定外源钙对樟子松幼苗过氧化氢和丙二醛的含量，超氧化物岐化酶、过氧化物酶、过氧化氢酶，H+-ATP和Ca2+-ATP酶的活性，明确外源钙对樟子松抗氧化酶系的影响；②测定樟子松针叶光合速率，蒸腾速率，气孔导度，胞间CO2浓度，Rubisco酶含量，水分利用效率等指标，明确不同干旱条件下樟子松针叶气孔运动对外源钙的响应，分析外源钙对樟子松针叶水分利用效率的调控机制，为阐明外源钙缓解樟子松水分胁迫的生理机制提供理论依据。

樟子松是辽西北半干旱区防风固沙的主要造林树种，近年樟子松人工林出现大面积衰退现象。大量研究表明水分亏缺是致使樟子松人工林衰退的主要原因。本项目通过控制试验，对樟子松幼苗进行不同浓度Ca2+和不同水分胁迫的双因素处理，从樟子松针叶光合特性、δ 13C和气孔运动角度研究水分胁迫条件下外源钙调控樟子松水分利用效率的作用及机制，为阐明外源钙缓解樟子松水分胁迫的生理机制提供理论依据，有助于建立干旱半干旱区樟子松人工林的合理经营对策。具体结论如下：.1）针叶光合-光响应曲线结果表明，5 mmol Cacl2处理能显著提高干旱胁迫下樟子松的光合能力；10 mmol Cacl2与不施钙处理均未能提高干旱胁迫樟子松的光合能力。2）针叶净光合速率、蒸腾速率和δ 13C值结果表明，5 mmol Cacl2处理能显著提高水分胁迫下樟子松幼苗的瞬时和长期水分利用效率；10 mmol Cacl2处理则没有相应作用。3）针叶气孔开度结果表明，樟子松针叶的气孔开度随着干旱胁迫的加剧先减小后增大，樟子松针叶气孔对水分胁迫的响应表明其具有等水植物的特性；Ca2+浓度的增加会引起樟子松针叶气孔的部分关闭；中度水分胁迫下，樟子松针叶气孔开度随着Ca2+的增加而显著减小，而重度水分胁迫下，樟子松针叶气孔开度没有显著变化。4）针叶光合-CO2响应曲线结果表明，5 mmol Cacl2处理显著提高了重度水分胁迫下樟子松针叶RuBP羧化酶活性，而10 mmol Cacl2处理与不施钙处理之间差异不显著。5）适宜浓度的Ca2+能够提高水分胁迫下樟子松幼苗的水分利用效率，并且随着水分胁迫程度的不同而具有不同的过程和途径：中度水分胁迫下，樟子松针叶光合气孔限制值上升和Ci值下降，表明Ca2+浓度增加致使气孔部分关闭是水分利用效率提高的主要原因。中度水分胁迫下樟子松针叶气孔开度随着Ca2+的增加而显著减小的结果进一步证实了这点；而在重度水分胁迫下，樟子松针叶光合气孔限制值下降并且Ci值上升，同时樟子松针叶RuBP羧化酶活性显著提高，表明此时Ca2+浓度增加引起叶肉细胞光合能力的上升是水分利用效率提高的主要原因。