Collaborative Research: Root Dynamics and Control in Heterogeneous Soft Substrates

植物的地上部分几乎只被研究过，很大程度上是因为与土壤生长的根有关的成像困难。因此，人们对根系结构和对植物健康至关重要的基质之间的相互作用知之甚少。根系适合于跨越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。植物根系对养分和水分的吸收、锚定和支撑以及土壤调节至关重要。这样的系统将空间和时间结合起来，在复杂的空间环境中取得卓越的成就。根必须通过细胞分裂从种子长成一个复杂的网络结构，而没有中央规划的最佳路径，以适应与不同粒径、湿度和压实度的基质的相互作用。最近，遗传学和测序以及土壤和凝胶土壤模拟物成像的进展已经开始阐明原理。然而，这些过程的实时交互动力学和控制决策在很大程度上是未知的。根尖生长与土壤相互作用的土壤动力学方面也在很大程度上没有得到研究。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Benfey，将致力于发现有效的根系探索、渗透和锚定的原理。这项工作将集中在具有良好遗传特征的水稻模型系统上，对多个品种进行一套比较和综合实验分析，并结合机器人物理和计算模型。更好地了解根系发育是在贫瘠土壤中提高作物产量的重要一步，这在面对快速气候变化时至关重要。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过去通过大众媒体和与当地博物馆和学校的互动与公众互动的成功，预计植物物理学（包括机器人物理学）可以用来产生对植物科学的广泛兴趣，这是纯植物学或植物遗传学无法做到的。为了发现新的相互作用，动力学和基因，根生长将在长度和时间尺度上进行监测，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。深入了解根系生长行为将通过时间依赖的压力，如紧实或松散的土壤，以及养分有效性的变化。通过细胞变化（如根增厚）来响应环境变化（如土壤压实）来控制生长的相关问题将会引起人们的兴趣。这种扰动将通过利用基因突变体来补充，以研究根动力学如何在关键行为（如环转）的修改后发生变化。为了更准确地模拟生命系统的各个方面，合作将开发实验验证的尖端驱动生物生长的计算模型，通过机械测试和机器人实验校准模拟的软物质相互作用方面。该项目由物理学部生命系统物理学项目和综合有机体系统学部生理与结构系统集群共同支持。该奖项反映了美国国家科学基金会的法定使命，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.