Collaborative Research: Root Dynamics and Control in Heterogeneous Soft Substrates

植物的地上部分几乎完全被研究，主要是由于与土壤生长的根相关的成像困难。因此，很少有人知道的相互作用的根结构和基质的植物健康至关重要。 根系统适合于跨长度和组织尺度的生命系统的综合研究，将基因组与微观和宏观表型性状和控制行为联系起来。植物根系对于养分和水分的吸收、固定和支撑以及土壤调理至关重要。这样的系统将空间和时间结合起来，以在复杂的空间环境中实现卓越。根必须通过细胞分裂从种子生长成复杂的网络结构，而无需集中规划最佳路径，并根据与不同粒径、湿度和压实度的基质的相互作用进行调整。最近，遗传学和测序的进展，加上土壤和基于凝胶的土壤模拟物中的成像，已经开始阐明原理。然而，这种过程的真实的时间相互作用动态和控制决策在很大程度上是未知的。根和土壤之间的顶端生长相互作用的地球动力学方面也在很大程度上未被研究。在这项合作提案中，两位专家，生物力学，机器人物理学和软物质物理学的Goldman和植物发育，遗传学和基因组学的Bennett，将致力于发现有效的根探索，渗透和锚定的原则。拟议的工作将集中在遗传上的良好特性的模型系统，水稻，多个品种的一套比较和综合实验测定加上robophysical和计算模型。更好地了解根系发育是提高贫瘠土壤作物产量的重要一步，在快速气候变化的情况下至关重要。与亚特兰大植物园的互动，研究兰花的生长将促进花园的保护活动。鉴于PI过去在通过大众媒体与公众交流以及与当地博物馆和学校的互动方面取得的成功，预计植物物理学（包括机器人物理学）可以用来产生广泛的兴趣，在植物科学的方式，纯植物学或植物遗传学不能.为了发现新的相互作用，动力学和基因，根生长将监测跨长度和时间尺度，利用X射线和凝胶系统成像（研究根尖动态生长行为）和共聚焦显微镜（用于细胞分裂和伸长），在控制良好的实验室土壤模拟物中改变不同的土壤性质和异质性。深入了解根生长行为将通过时间依赖性应力，如压实或松散的土壤，以及养分供应的变化。与通过细胞变化（如根增厚）响应环境变化（如土壤压实）控制生长相关的问题将是感兴趣的。这种扰动将补充利用遗传突变体，以研究根动力学如何改变后，修改的关键行为，如回旋。为了更准确地模拟生命系统的各个方面，该合作将开发经过实验验证的尖端驱动生物生长的计算模型，校准软-通过机械测试和机器人实验模拟的物质相互作用方面。该项目由物理学系的生命系统物理学项目和综合物理学系的生理和结构系统集群共同支持。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The above-ground portion of plants has been almost exclusively studied largely due to imaging difficulties associated with soil-growing roots. Thus, little is known about the interaction of root architectures and substrates critical to plant health. The root system is amenable to integrated study of a living system across length and organizational scales, linking genomic to micro and macroscopic phenotypic traits and control behaviors. Plant root systems are vital for nutrient and water absorption, anchoring and support as well as soil conditioning. Such systems couple space and time to achieve excellence in complex spatial environments. Roots must grow from a seed into a complex network structure via cell division without central planning of optimal paths, adjusting to interactions with substrates of varying particle size, moisture, and compaction. Recently, advances in genetics and sequencing coupled with imaging in soil and gel-based soil mimics have begun to elucidate principles. However, real time interaction dynamics and control decisions for such processes are largely unknown. The terradynamic aspects of tip-growth interactions between root and soil are also largely unstudied. In this collaborative proposal two experts, Goldman in biomechanics, robophysics and soft matter physics, and Benfey in plant development, genetics and genomics, will work to discover principles of effective root exploration, penetration and anchoring. The proposed work will focus on the genetically well-characterized model system, rice, subjecting multiple cultivars to a suite of comparative and integrative experimental assays coupled with robophysical and computational models. A better understanding of root system development is an important step towards increasing crop yields in poor soils, critical in the face of rapid climate change. Interaction with Atlanta Botanical Gardens to study orchid growth will facilitate the Garden's conservation activities. Given the PIs' past success in interfacing with the public via popular press and interaction with local museums and schools, it is expected that the physics of plants (including robophysics) can be used to generate broad interest in plant science in a way that pure botany or plant genetics cannot.To discover novel interactions, dynamics and genes, root growth will be monitored across length and time scales, imaging with x-ray and gel systems (to study root tip dynamic growth behaviors) and confocal microscopy (for cell division and elongation) varying different soil properties and heterogeneities in well-controlled laboratory soil-mimics. Insight into root growth behaviors will be obtained via time-dependent stresses such as compacted or loose soil, as well as changes in nutrient availability. Questions associated with control of growth via cellular changes (e.g. root thickening) in response to changes in environment (e.g. soil compaction) will be of interest. Such perturbations will be complemented by utilizing genetic mutants to study how root dynamics change upon modification of key behaviors such as circumnutation. To more accurately model aspects of the living systems, the collaboration will develop experimentally validated computational models of tip-driven biological growth, calibrating the soft-matter interaction aspects of the simulation via mechanical tests and robot experiments.This project is being jointly supported by the Physics of Living Systems program in the Division of Physics and the Physiological and Structural Systems Cluster in the Division of Integrative Organismal Systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.