(A-D) Floral bud morphology in the MF line from the microspore mother cell stage to the mature pollen stage. (E) A MF dehiscent anther with normal oval pollen grains (inset shows the mature pollen grains). (F-I) Floral bud morphology in the Ogura-CMS line from the microspore mother cell stage to the mature pollen stage. (A, F) Microspore mother cell stage and tetrad stage. (B, G) Uninucleate stage. An Ogura-CMS floral bud exhibits the same morphology as a MF bud. (C, H) Bicellular stage. The withered anthers of the Ogura-CMS line are evident, compared with the lump anthers of the MF line. (D, I) Dehiscent stage. The MF anthers split open along the stomium, whereas the collapse of the Ogura-CMS anthers is evident. (J) An Ogura-CMS anther without any pollen grains. Bars = 1 mm in (A, B, E-H), 2 mm in (C, D, I), 500 μm in (J).