Photosynthesis and Phloem Anatomy

拟议的工作旨在改善目前对决定和可能限制植物最大光合作用速率和生产力的因素的不完整理解。通过结合生理和解剖评估，将测试植物光合作用的最大速率与可能决定叶片糖输出（韧皮部）血管能力的特定解剖特征之间是否存在基本关系。糖的出口有时会对整个植物的碳分布造成瓶颈，从而影响植物的生产力。特别是，叶片加载叶脉密度和每个出口韧皮部血管的加载细胞的比例将在不同韧皮部加载机制的物种中进行评估。如果能够建立光合能力和韧皮部特征之间的关系，这些特征将可用于：(i)识别具有优越光合性能和生产力的植物物种和品种；（ii）为未来的工程工作提供信息，旨在操纵这些解剖特征以提高植物生产力。此外，还将确定在干燥条件和/或低温条件下，高负载矿脉密度等特征是否与提高产能有关。如果这种优势能够确立，这将有助于在全球气候变化下正在扩张的温暖/干旱地区，以及在目前全球变暖趋势下作物种植正在扩张的高纬度和高海拔地区，以及植物将经历比通常温度更冷的季节性暴露的地区，选择具有优越生产力的植物。从这项工作中获得的知识将有助于维持和提高作物生产力以及碳封存，鉴于人口的迅速增长以及当前和预计的气候变化的影响，这些都是迫切的目标。此外，pi将利用其现有的联系，招收来自不同背景的学生参加拟议的研究和由此产生的出版/传播工作以及外联工作。最后，新闻机构计划继续在包括非专业人士在内的广大读者的场所进行出版活动。

The proposed work seeks to improve the currently incomplete understanding of factors that determine, and may limit, plants' maximal rates of photosynthesis and productivity. By combining physiological and anatomical assessments, it will be tested whether there is a fundamental relationship between the maximum rate of plant photosynthesis and specific anatomical features that may be determinants of the capacity of leaves' sugar-exporting (phloem) vessels. Sugar export may sometimes present a bottleneck to carbon distribution throughout the plant and thus to plant productivity. In particular, leaf loading vein density and the ratio of loading cells per exporting phloem vessel will be assessed in species with different mechanisms of phloem loading. If a relationship between photosynthetic capacity and phloem features can be established, these features will be available to: (i) identify plant species and varieties with superior photosynthetic performance and productivity; (ii) inform future engineering efforts directed at manipulating these anatomical features to enhance plant productivity. It will furthermore be established whether features such as high loading vein density are associated with enhanced productivity under dry conditions and/or cool temperatures. If such an advantage can be established, this will aid in the selection of plants with superior productivity in warm/arid regions that are expanding under global climate change and at higher latitudes and altitudes into which crop cultivation is expanding under the present global warming trend and where plants will experience seasonal exposure to colder than usual temperatures. The knowledge gained from this work will aid in the effort to maintain, and improve, crop productivity as well as carbon sequestration, which are urgent goals given the burgeoning human population as well as the current and projected impact of climate change. Furthermore, the PIs will utilize their existing connections to recruit students from diverse backgrounds into the proposed research and resulting publication/dissemination efforts as well as for outreach efforts. Lastly, the PIs are planning to continue their publication activity in venues reaching a broad audience including non-specialists.