The intricate intracellular structure of a rice mesophyll cell

Rice (Oryza sativa) leaf blades possess lobed mesophyll cells with intricate cell boundaries. Their sub-cellular structure has been observed with transmission electron microscopy (TEM) of thin sections, but the whole three-dimensional (3D) structure has not been reconstructed.

Three-dimensional (3-D) models of a rice mesophyll cell.
Three-dimensional (3-D) models of a rice mesophyll cell. (A) 3-D volume rendering of the image stack containing a whole rice mesophyll cell (x = 20 μm, y = 20 μm, z = 9 μm). (B) 3-D surface modelling of a rice mesophyll cell showing the concave–convex exterior of the cell wall. (C) Six different angle views of (B). The numbers indicate the section number from the first cut, corresponding to the numbers in Fig. 2. The mesophyll cell was discoid shape, having several lateral protuberances; the maximum length on the x- and y-axes was approximately twice that on the z-axis. (D) Slice view of the 3-D model of the rice mesophyll cell shown in (B) and (C). Chloroplasts (green) line almost all the inside surface of the cell wall (golden yellow), and the spherical nucleus (magenta) is located inside them. (E) Configuration of chloroplasts in the rice mesophyll cell shown in (B). Each chloroplast is displayed in a different colour. This cell contains 13 chloroplasts. Cutting interval = 50 nm. Total number of cuttings = 176.

Oi et al. examine whole rice mesophyll cells using a Focus Ion Beam Scanning Electron Microscope (FIB-SEM). The 3-D reconstructed cell models were discoid-shaped, comprising several lobes around the cell periphery, with chloroplasts spread as sheets along the cell lobes and occupying half of the cell volume. The cell shape and chloroplast distribution enhances the leaf area available for CO2 absorption.

Further reading

Oi, T., Enomoto, S., Nakao, T., Arai, S., Yamane, K., & Taniguchi, M. (2017). Three-dimensional intracellular structure of a whole rice mesophyll cell observed with FIB-SEM. Annals of Botany, 120(1), 21–28.