Biophysical interactions at the root-soil interface governing plant growth

Most terrestrial plants rely on their root system to acquire water and nutrients from soil, which are vital resources for plant growth and thus global agricultural productivity. In addition, roots are a major source of organic matter input to soil, thereby fuelling heterotrophic soil life and biogeochemical cycles. Thus, plant roots play a crucial role for numerous ecosystem functions provided by soil including biomass production, water and nutrient cycling and storage, and carbon sequestration. However, our understanding of the interactions between soil properties and root physiological processes underpinning the functioning of terrestrial ecosystems remain incomplete. The goal of my research is to gain novel insights into the interactive effects between soil physical properties and root physiological processes on whole plant growth and associated functions of agroecosystems.

In order to gain access to water and nutrient pools, plants need to extend their root system into soil. Root growth as well as root maintenance require significant amounts of carbon, which needs to be translocated from the shoot to the root system. Soil mechanical impedance, a metric describing the hardness of the soil, and soil aeration have both direct implications for root growth rate and the carbon demands of plant root systems. Mechanical impedance determines the pressure roots need to exert in order to penetrate soil, while soil aeration regulates gas exchange between roots and the surrounding soil. Root growth rate decreases and the carbon demands of plant root system increase upon high soil mechanical impedance and poor soil aeration, thereby reducing whole plant growth. Moreover, soil mechanical impedance and soil aeration are not constant but vary in space and time due to spatial differences in soil porosity and pore size distribution, and temporal fluctuations in soil moisture. Hence, plant roots inhabit a highly heterogeneous physical environment and this heterogeneity is key to plant growth and associated ecosystem functions.

In this docent lecture, I will present an interdisciplinary framework combing soil physics with plant eco-physiology and genetics to elucidate the role of biophysical interactions at the root-soil interface for whole plant growth. Deploying experimental and theoretical approaches, I will show how soil physical properties and their spatiotemporal heterogeneity interact with root physiological processes and how these interactions contribute to plant growth and associated ecosystem functions. Furthermore, I will demonstrate how root phenotypic diversity can be exploited to increase the tolerance of crops to soil physical stress such as high mechanical impedance and poor soil aeration. Finally, I will outline how the presented framework can be extended in future research to include effects of climate change and interactions of plants with heterotrophic soil organisms on root physiology and crop performance.