Collaborative Research: Physiology of Long Distance Assimilate Transport

地球上生命的基础是通过植物中的光合作用将太阳能转化为化学能。光合作用的高能量最终产物是糖，它必须通过一种叫做韧皮部的组织从产生部位（大多数情况下是叶子）转移到消耗和储存部位（茎、根、果实）。人类要么直接以沙拉、谷物、蔬菜等形式消耗能量丰富的植物组织，要么间接地通过消耗动物消耗植物产生的肉来消耗能量。韧皮部内糖的转运是生产优质、高产、健康食品的关键机制。例如，如果通过韧皮部输出的糖不足，植物的光合作用就会主动减少。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，这导致了产量的损失。植物病毒通过韧皮部传播，对植物造成严重损害。尽管韧皮部在植物生长性能和食物生产中发挥着核心作用，但人们对韧皮部装载和运输的潜在过程知之甚少。该项目将研究糖通过叶片的流动路径，糖进入或“装载”到韧皮部以及糖在植物内部的分布。加强对韧皮部负荷和运输的了解，可以产生新的战略，通过减少或消除使用农药的必要性来保护植物免受害虫侵害，提高作物产量和生产更健康的食品。该奖项的目标是研究韧皮部负载的生理参数和具有长韧皮部网络的植物（葡萄藤和树木）的运输物理。在以前的奖励中开发的方法将用于生成基于细胞和组织类型的叶子图，概述不同静脉顺序的膨胀压力和韧皮部流动模式。此外，还将绘制细胞和组织之间的胞间连丝分布，以及从源细胞到筛管的细胞间电导率。测量筛管膨胀和流速的新系统，以及直接基于扫描电镜的方法将用于收集等离子体频率和筛板结构的数据。研究了不同负载类型下树木和藤本植物大小与源胀压和韧皮部结构的关系。这将使目前的韧皮部运输模型重新参数化，以便更好地反映光同化物质通过植物运输途径的水力结构。该奖项还将汇集专门研究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，以及吸引本科生参与研究，并为高中生和教师提供了解植物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.