作用于小孢子发生期间 During microsporogensis ●减数分裂meiosis 0 单核早中期Early and middle microspore stage ●二核晚期Late bicellular pollen stage Most cases 20 20 作用于小孢子发生期间 During microsporogensis ●减数分裂 meiosis ●单核早中期 Early and middle microspore stage ●二核晚期 Late bicellular pollen stage Most cases