Collaborative Research: Physiology of Long Distance Assimilate Transport

地球上生命的基础是通过在植物中发生的光合作用过程将太阳能转化为化学能。光合作用的高能最终产物是糖，它必须通过一种叫做韧皮部的组织，从产生地点(大多数情况下是叶子)转移到消耗和储存的地点(茎、根、果实)。人类要么以沙拉、谷物、蔬菜等形式直接消耗富含能量的植物组织，要么间接通过消耗植物的动物生产的肉类来消耗。韧皮部中糖的运输是生产优质、高产和健康食品的关键机制。例如，如果通过韧皮部的糖输出不足，植物的光合作用就会被积极地降低。像蚜虫这样的害虫攻击韧皮部，将它们的口器插入组织，并以富含糖的溶液为食，这会导致产量损失。植物病毒通过韧皮部传播，对植物造成严重损害。尽管韧皮部在植物表现和食物生产中起着核心作用，但人们对韧皮部装载和运输的基本过程知之甚少。这个项目将调查糖通过叶子的流动路径，进入或“装载”到韧皮部的糖，以及糖在植物中的分布。加强对韧皮部装载和运输的了解可能导致新的战略，通过减少或消除使用杀虫剂的必要性来保护植物免受虫害，提高作物产量和生产更健康的食物。该奖项的目标是研究韧皮部装载的生理参数和具有长韧皮部网络的植物(藤本植物和树木)的运输物理。在以前的奖项中开发的方法将被用来生成基于细胞和组织类型的叶片地图，以不同的脉序勾勒出膨胀压力和韧皮部流动模式。此外，还将绘制胞间连丝在细胞和组织之间的分布，以及从源细胞到筛管的细胞间传导性。测量筛管膨胀率和流速的新系统，以及直接基于扫描电子显微镜的方法，将被用来收集关于等离子体键频率和筛板结构的数据。还将研究不同负载类型的树木和藤本植物的植株大小与源膨压和韧皮部构型的关系。这将使目前的韧皮部运输模型重新参数化，以便更好地反映通过植物的光合作用同化物运输途径的水力结构。该奖项还将汇集专门从事植物细胞生物学和维管运输的研究人员，支持博士后研究人员和研究生的教育和培训，并让本科生参与研究，为高中生和教师提供了解植物中光同化物运输的机会。

The basis for life on earth is the conversion of solar energy into chemical energy by a process called photosynthesis that takes place in plants. The high energy containing end product of photosynthesis is sugar that has to be translocated, via a tissue called phloem, from the site of generation (in most cases leaves) to the sites of consumption and storage (stems, roots, fruits). Humans either consume energy rich plant tissues directly in the form of salads, cereals, vegetables etc., or indirectly via the consumption of meat, which was produced by animals consuming plants. The translocation of sugars within the phloem is a key mechanism in the production of high quality, high yield, and healthy food. For example, photosynthesis is actively reduced by the plant if export of sugars through the phloem is insufficient. Pests like aphids attack the phloem, insert their mouthparts into the tissue and feed on the sugar rich solution, which results in loss of production. Plant viruses travel through the phloem and cause severe damage to the plant. Despite the central role the phloem plays in plant performance and food production, the knowledge of the underlying processes of phloem loading and transport are poorly understood. This project will investigate the flow path of sugars through leaves, the entry or "loading" of sugars into the phloem and the distribution of sugars within the plant. Enhanced understanding of phloem loading and transport could lead to new strategies to protect plants from pests, to increase crop yield and to produce healthier food by reducing or eliminating the necessity for application of pesticides.The goal of this award is to investigate physiological parameters of phloem loading and the physics of transport in plants with long phloem networks (vines and trees). Methods developed during previous awards will be used to generate cell and tissue-type based maps of leaves outlining turgor pressure and phloem flow patterns in different vein orders. In addition, the distribution of plasmodesmata between cells and tissues, and cell-to-cell conductivity from source cells to sieve tubes will be mapped. New systems to measure sieve tube turgor and flow velocity, as well as straightforward SEM based methods will be used to gather data on plasmodesmal frequencies and sieve plate structure. The relationship between plant size and source turgor pressure and phloem architecture in trees and vines with different loading types will also be investigated. This will allow current models of phloem transport to be re-parameterized so as to reflect better the hydraulic architecture of the pathway for photoassimilate transport through the plant. This award will also bring together researchers specializing in plant cell biology and vascular transport, and support education and training for a postdoctoral researcher and graduate students, as well as engage undergraduates in research and provide opportunities for high-school students and teachers to learn about the transport of photoassimilates in plants.