Dynamics of Plant Root Functions

Roots of living plants support photosynthesis, growth and reproduction. Water capture is paramount; 100 to 600 water molecules fix one carbon dioxide in photosynthesis. Along with water, roots deliver nitrogen and other essential nutrients to leaves, while acting as a barrier for toxic soil chemicals and pathogens. The timing and spatial capture of water and nutrient supply is critical to productivity. This talk covers our research on the dynamics of root system functions, as they emerge from non-invasive phenotyping technologies, molecular biology and modeling. Dynamics can arise from (1) growth and differentiation processes, and (2) soil conditions. Growth and differentiation determine system architecture, vascular networks, and specialisation of tissues for functions. Soil conditions determine availability of resources and functions carried out by the roots. Root-associated microbiota may act by directly or indirectly (via signals to shoots) modulating root dynamics. Additionally, multiple soil properties influence development of root surface cells (Kant, unpublished), and transient changes trigger rapid subcellular responses. For example, Zn re-supply promotes a crest of protein synthesis and degradation, including membrane transport changes within existing cells, within 30 minutes of exposure (Arsova, unpublished). Carbon imaging in live plants using Positron Emission Tomography indicates root systems have variably-distributed, recently-fixed, photosynthetic carbon, but a nitrate supply promotes a global distribution within hours (Metzner, unpublished). Magnetic Resonance imaging of whole plants shows water uptake rates vary within hours of watering after drought, depending on plant genotype (Schneider, unpublished). Crops constantly face non-steady supplies of rain, irrigation and inputs scheduled with agronomic management technologies. Plant phenotyping can quantify whole plants overtime to breed for genotypes with dynamics optimised to inputs and their capture. There is an exciting need to understand the dynamics of root functions and how they couple to resource inputs and shoot demands.