Fig. 1

Cytological observations of apomixis in Zanthoxylum bungeanum. a Different developmental stages of the Zanthoxylum bungeanum fruit. b Cytological observation of apomixis in Zanthoxylum bungeanum. (i-ii) The megaspore mother cell is formed in the S1. (iii) The binuclear embryo sac is formed in the S2. (iv-v) The embryo sac decomposes, and the nucellus cells develop into the adventitious primordial embryo in the S3. (vi) The adventitious primordial embryo develops into a nucellus embryo in the S4. Scale bars = 20 μm. c A model diagram of adventitious embryogenesis in Zanthoxylum bungeanum. ae: adventitious embryo, ap: antipodals, ape: adventitious primordial embryo, bes: binuclear embryo sac, eg: egg, es: embryo sac, mmc: megaspore mother cell, nc: nucellar cell, ne: nucellus embryo, neic: nucellar embryo initial cells, ov: ovule, pn: polar nuclei, sy: synergids