Collaborative Research: Light Enhanced 13C Enrichment of Dark Respired CO2: Implications for Leaf Internal CO2 Conductance and Respiration in the Light

叶片内部的阻力限制了光合作用对二氧化碳的吸收，影响了作物和其他植物对水和肥料的利用效率。这种效率还受到光合作用和呼吸作用如何通过共享反应物和产物相互作用的影响。该项目将通过分析叶片如何不同地利用二氧化碳中的重、轻碳同位素，来研究叶片对二氧化碳扩散的抗性，以及光合作用和呼吸作用之间的相互作用。随着一项新技术的发展——可调谐二极管激光光谱仪（TDL），这项任务变得更容易、更快、更便宜。最近的发现表明，在黑暗期之前立即向树叶提供高光强度可以对黑暗期间的同位素交换产生很大影响。这意味着磷酸烯醇丙酮酸羧化酶（PEPC）的作用比预期的更大，这可能会影响用于测量叶片内部对二氧化碳扩散的抵抗力以及光合作用和呼吸作用之间相互作用的同位素数据的解释。将分析木本和草本物种碳同位素利用的日和季节变化，以及含有大量PEPC的植物。本研究将有助于明确PEPC在控制植物同位素利用及其对光合和呼吸相互作用的影响中的作用。更广泛的影响：除了潜在的作物改良外，对叶片内同位素交换的了解的增加将完善用于理解生态系统代谢的基本假设，并产生模拟区域碳循环所需的数据。TDL使用简单，价格低廉，是新墨西哥大学（一所少数民族服务机构，新墨西哥大学生物学1300名专业中有36%是西班牙裔，另外7%是美洲原住民）和波特兰州立大学（许多学生是家庭中第一个上大学的成员或非传统的重新入学学生）的研究生和本科生的课堂教育和实验室培训的理想选择。使用该设备的经验将帮助学生为在大学、国家实验室和私营部门从事研究工作做好准备。

The resistances inside leaves that restrict the uptake of CO2 by photosynthesis impact how efficiently crops and other plants use water and fertilizers. This efficiency is also impacted by how photosynthesis and respiration interact through sharing of reactants and products. This project will examine the resistances to CO2 diffusion in leaves and interactions between photosynthesis and respiration through analyses of how leaves differentially use heavy and light isotopes of carbon in CO2, a task that has become easier, faster, and less expensive with the development of a new technology - the tunable diode laser spectrometer (TDL). Recent discoveries suggest that providing high light intensities to a leaf immediately preceding a dark period can have a large effect on the exchange of isotopes during darkness. This implies a larger role of the enzyme phosphoenolpyruvate carboxylase (PEPC) than is expected and this could impact interpretation of isotopic data used to measure internal leaf resistance to CO2 diffusion and interactions between photosynthesis and respiration. Daily and seasonal variation in carbon isotope usage by woody and herbaceous species will be analyzed along with plants containing high amounts of PEPC. This study will help to define the role of PEPC in controlling isotopic usage by plants and its influence on photosynthetic and respiratory interactions.Broader impacts: In addition to potential crop improvements, increases in understanding of isotopic exchange within leaves will refine the fundamental assumptions used to understand ecosystem metabolism and generate data needed to model regional carbon cycles. The TDL is straightforward and inexpensive to use making it ideal for classroom education and laboratory training of graduate and undergraduate students at the University of New Mexico (a Minority Serving Institution where 36% of UNM Biology's 1300 majors are Hispanic and another 7% are Native American) and at Portland State University (where many students are the first member of their family to attend college or are non-traditional re-entry students). Experience with this equipment will help prepare students for research careers at universities, national labs, and in the private sector.