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. 2021 Feb 10;12:634114. doi: 10.3389/fpls.2021.634114

FIGURE 2.

FIGURE 2

The middle layer is derived from both inner secondary parietal (ISP) and outer secondary parietal (OSP) cells in the anther. (A) Model of the origin of the middle layer. The first model shows periclinal division in ISP cells to form the endothecium and middle layer. The second model shows periclinal division in OSP cells to form the tapetum and middle layer. The last model shows periclinal division in both OSP and ISP cells. (B) Images of Col-0 anthers stained with CW at stages 3, 4, and 5. The images in the left column show the CW signals. The images in the middle showed bright field signals. The right images are the merged signals of Calcoflour white (CW) and the bright field. Arrow shows the newly formed cell wall. Stage 4 divided: the anther finished periclinal division at stage 4 with the middle layer fully formed. Stage 4 division: the anther was undergoing periclinal division. The middle layers were derived from inner secondary parietal cells (ISPs), outer secondary parietal cells (OSPs), and both inner secondary parietal cells and outer secondary parietal cells (ISPs and OSPs) in the same anther. Scale bar = 10 μm. (C) Fluorescence images of Col-0 anthers stained with 4′,6-diamidine-2-phenylindole (DAPI) at stage 4. The images in the left column show the DAPI signals. The images in the middle showed bright field signals. The right images merge the DAPI signals and the bright field signals. Scale bar = 10 μm. (D) The statistics of CW staining anthers undergoing periclinal division in stage 4. ISP: middle layer derived from inner secondary parietal cells. OSP: middle layer derived from outer secondary parietal cells. ISP and OSP: middle layer derived from both inner secondary parietal cells and outer secondary parietal cells in the same anther.