Combining flow-MRI method and modeling approach to assess the impact of conducting tissues on water fluxes in tomato fruit

Water and carbon status throughout growth and development are tightly controlled by the plants and are key components of their response to environmental stresses. In order to predict the plant behavior under contrasting environments, many functional-structural plant models have been developed, describing the network of source and sink organs as well the transport of resources within this network. However, some parameters related to the regulation of local endogenous resource availability and transport are difficult to measure in planta. Only a limited number of the existing techniques are non-invasive and feasible. Yet nuclear magnetic resonance (NMR) spectroscopy, relaxometry and imaging (MRI) methods are available to study cell water balance and phloem and xylem transports in large potted plants. The objective of this study is to gain a better understanding of the impact of conducting tissues on water fluxes in tomato fruit by combining modeling, MRI and histological observations. In order to measure water flux, we implemented a novel flow-MRI method taking advantage of inflow slice sensitivity. We applied these methods to estimate water fluxes at the truss peduncle and fruit pedicel. The experiments have been performed on an Agilent MRI scanner working at 9.4T using inflow and outflow sensitive spin echo pulse sequences. We compared MRI measurements to the predictions of a biophysical model that simulates fruit growth. Our study shows that MRI is a useful and non-destructive technique to measure water fluxes at different locations within the plant. Combined to histological measurements, we can obtain quantitative data at the vessel level to improve model formalisms and parameterization and go beyond the limits of current approaches in plant ecophysiology.