*3.3. Transmission Electron Microscopy (TEM)*

The WT and *oscaf1* seedlings were grown in growth chambers, as above. The transmission electron microscopy (TEM) analysis was performed according to a previous study [23]. Briefly, the third leaves from WT and *oscaf1* were collected and cut into approximately 0.5 cm2 pieces. Leaf samples were fixed using 2.5% glutaraldehyde and 1% OsO4, dehydrated using an ethanol series, and embedded in resin. The samples were stained again with uranyl acetate and alkaline lead citrate and finally observed under a HitachiH-7500 TEM (Tokyo, Japan).
