• Climacteric ripening of tomato fruit is initiated by a characteristic surge of the production rate of ethylene, accompanied by an increase in respiration rate. As both activities consume O₂ and produce CO₂, gas concentration gradients develop in the fruit that cause diffusive transport. This may, in turn, affect respiration and ethylene biosynthesis. Gas diffusion in fruit depends on the amount and connectivity of cells and intercellular spaces in 3D.
• We investigated micromorphological changes in different tomato tissues during development and ripening by visualizing cells and pores based on high-resolution micro-computed tomography, and computed effective O₂ diffusivity coefficients based on microstructural features of the tissues.
• We demonstrated that mesocarp and septa tissues have larger cells but small and more disconnected pores than the placenta and columella, resulting in relatively lower effective O₂ diffusivity coefficients. Cell disintegration occurred in the mesocarp and septa during ripening, indicating lysigenous air pore formation and resulting in a gradual increase of the effective O₂ diffusivity.
• The results suggest that hypoxic conditions caused by the increasing size and, hence, diffusion resistance of the growing fruit may induce an increase of tissue porosity that results in a greatly enhanced O₂ diffusivity and, thus, helps to alleviate them.

中文翻译：

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微结构变化增强了番茄（Solanum lycopersicum）果实成熟和成熟过程中的氧气运输

• 番茄果实的更年期成熟是由乙烯产生速率的特征性激增引发的，伴随着呼吸速率的增加。由于这两种活动都会消耗 O ₂并产生 CO ₂，因此水果中会产生气体浓度梯度，从而导致扩散传输。反过来，这可能会影响呼吸和乙烯的生物合成。水果中的气体扩散取决于 3D 中细胞和细胞间空间的数量和连通性。
• 我们通过基于高分辨率微型计算机断层扫描的细胞和孔隙的可视化研究了不同番茄组织在发育和成熟过程中的微形态变化，并根据组织的微观结构特征计算了有效的 O ₂扩散系数。
• 我们证明中果皮和隔膜组织比胎盘和小柱具有更大的细胞但更小且更不连通的孔，导致相对较低的有效O ₂扩散系数。在成熟过程中，中果皮和隔膜中发生细胞解体，表明形成了产气孔并导致有效O ₂扩散率逐渐增加。
• 结果表明，由增大的果实尺寸引起的缺氧条件以及生长中果实的扩散阻力可能会导致组织孔隙率的增加，从而导致O ₂扩散率大大提高，从而有助于缓解它们。