*3.6. Scanning Electron Microscopy*

Scanning electron microscopy was conducted as previously described with some modifications [92]. The lamina joints of flag leaves of WT and *osbhlh079-D* at heading stage grown under NLD conditions in the paddy field were excised and sectioned longitudinally as previously described [56]. The samples were fixed with modified Karnovsky's fixative (2% paraformaldehyde, 2% glutaraldehyde, and 50 mM sodium cacodylate buffer, pH 7.2) at 4 ◦C for 24 h, and washed with 50 mM sodium cacodylate buffer (pH 7.2) three times at 4 ◦C for 10 min each. Next, the samples were post-fixed at 4 ◦C for 2 h with 1% osmium tetroxide in 50 mM sodium cacodylate buffer (pH 7.2), and washed twice with distilled water at room temperature, followed by dehydration with a gradient series of ethanol. After dehydration, the samples were processed as follows: dried in liquid CO2 using a critical point dryer

(EM CPD300, Leica, Germany), and coated with platinum using a sputter coater (EM ACE200, Leica, Austria). The processed samples were observed by scanning electron microscope (AURIGA, Carl Zeiss, Germany).
