Investigation of the structural, physiological, and biophysical premises for assimilate allocation in plant sinks

植物是我们这个星球上的主要生产者。光合作用的机制使它们能够将气体(二氧化碳)和液体(H2O)转化为富含能量的固体糖。然后，这种糖可以用来为细胞功能提供燃料，也可以作为植物结构组件(如木材)的构建块。它也是所有人类食物来源的基础。人们对光合作用的过程有很好的研究和理解。然而，绝大多数糖并没有在其光合作用产生的地方(叶片)被利用，而是被转移到远处的组织中。例如，除了生菜等少数例外，人类不吃树叶，而是吃根、水果、种子等。另一个例子是木材，它已经被使用了几个世纪，是我们文明的基本材料之一。将糖从光合作用部位输送到储存和利用部位的组织称为韧皮部。韧皮部运输比光合作用少得多的研究和理解。这个项目将研究定义通过韧皮部的糖传递的位置和数量的机制。理解这些机制的最终目标是引导韧皮部运输到特定的位置，以提高食物或生物质的生产。维管系统使生物能够通过大量流动在内部分配资源，从而克服扩散所设置的大小限制。在植物中，维管组织的进化使树木得以发展，并伴随着陆地生态系统生产力的大幅增加。韧皮部将光合作用的产物分配到整个植物中，从而形成非光合作用的结构。韧皮部卸载过程在将光同化物分配到库中起着关键作用，库以种子、块茎、根等形式代表着人类的主要食物来源。然而，对韧皮部卸载部位分配控制的细胞过程研究较少，也知之甚少。该项目旨在阐明韧皮部卸载的结构、生理和生物物理基础，未来的目标是控制同化物分配到库中，以改良粮食作物和生物能源作物。该项目将利用新开发的技术，如现场流动和卸载观测和高分辨率连续块面成像，以创建各种植物物种的韧皮部卸载机制的详细了解。

Plants are the primary producers on our planet. The mechanism of photosynthesis allows them to turn a gas (CO2) and a liquid (H2O) into energy-rich solid sugars. The sugar can then be used to fuel cellular functions and also as a building block for structural plant components such as wood. It is also the basis for all human food sources. The process of photosynthesis is well studied and understood. However, the vast majority of sugars are not utilized at the place of their photosynthetic production (the leaves), but are translocated to distant tissues. For example, with a few exceptions such as lettuce, humans do not eat leaves, but roots, fruits, seeds etc. Another example is wood, which has been used for centuries and is one of the fundamental materials in our civilization. The tissue that transports the sugars from the site of photosynthesis to the site of storage and utilization is called phloem. Phloem transport is much less well studied and understood than photosynthesis. This project will investigate the mechanisms that define the location and amount of sugar delivery that happens through the phloem. The ultimate goal of understanding these mechanisms is to direct phloem transport to specific locations to improve food or biomass production.Vascular systems enable organisms to distribute resources internally by bulk flow and thus to overcome size limitations set by diffusion. In plants, the evolution of vascular tissues enabled the development of trees and was accompanied by a major increase in the productivity of terrestrial ecosystems. The phloem distributes the products of photosynthesis throughout the plant, allowing non-photosynthetic structures to be formed. The process of phloem unloading plays a critical role in allocating photoassimilates to sinks which in the form of seeds, tubers, roots etc. represent the major food sources for humans. The cellular processes of allocation control at the sites of phloem unloading, however, are understudied and poorly understood. This project aims at elucidating the structural, physiological, and biophysical basis for phloem unloading with the future goal of controlling allocation of assimilates to sinks for the improvement of food- and bioenergy crops. The project will utilize newly developed techniques such as in situ flow and unloading observations and high resolution serial block face imaging to create a detailed understanding of the mechanisms of phloem unloading in various plant species.