S06 - Session P10 - Session - Microstructure of tissues reveals oxygen diffusion pathways in ripening tomato fruit

Authors: Hui Xiao *, Pieter Verboven, Bart Nicolaï

As one of the key factors for C 2 H 4 biosynthesis during fruit ripening, local O 2 concentration inside tomato fruit is affected by both diffusion and consumption (respiration). Our previous studies have found substantial microstructural differences among different tissue types and ripening stages, which affects gas diffusion rates for respiratory gases and eventual internal gas levels [1]. In this study, the effective gas diffusion coefficient (diffusivity) of respiratory gases O 2 and CO 2 of tomato tissues (i.e. mesocarp, septa, placentaand columella) during development and ripening were computed using a microscale gas diffusion pore-network model based on X-ray µ-CT images. In this model, the microstructure of a tissue was translated to a pore scale network containing nodes (each node represents a single cell cluster or pore) connected by biconical channels , the effective diffusivity was then calculated by the computed flux for a set concentration gradient across the sample [2]. The simulation results showed that the gas diffusivity of placenta and columella tissues was higher than that of mesocarp and septa for both gases due to higher porosity and pore connectivity. In placenta and columella tissues, the diffusivity was higher for O 2 than for CO 2 , while in mesocarp and septa tissues without open pores, the diffusivity was higher for CO 2 than for O 2 and both Combined with respiration kinetics, these results will be further used in fruit gas exchange models to reveal the gas distribution within an entire tomato fruit to help understand ethylene biosynthesis and ripening processes.