A malformation of sex-changing plant Arisaema serratum (Araceae) produces both male and female inflorescences

ABSTRACT

The genus Arisaema (Araceae) can change sex expression between male and female with increasing plant size (sequential hermaphrodism). As most Arisaema species have only one inflorescence on each individual, sex expression is seemingly determined at the individual level. However, malformations with male and female inflorescences have occasionally been observed. Unfortunately, their developmental origin is unclear because of a lack of detailed descriptions of the shoot structure. To estimate the unit of sex determination in Arisaema, we observed the morphology of an aberrant individual of Arisaema serratum (Thunberg) Schott with multiple inflorescences for three years. In the second year, the aberrant individual produced pure male and female inflorescences. Based on the phyllotactic pattern of this malformation, we estimated that the inflorescences were duplicated due to a broadening of the apical meristem via fasciation. Contrary to other Arisaema plants with multiple inflorescences reported previously, the corm of the aberrant individual did not subdivide nor branch spontaneously after the growing season for three years. Thus, duplicated inflorescences presumably shared the resource supply without physiological partitioning during sex determination. These results imply that sex expression is determined at the inflorescence level but not at the individual or floret levels in dioecious Arisaema.

KEYWORDS:

• Fasciation
• labile sex expression
• ontogenetic sex change
• phyllotaxis
• teratology

Acknowledgments

We thank Miyu Adachi, Satomi Hara, Yuka Nakamura, and Kazuhiro Yamada for their support of the field survey; Shungo Kariyama for the reception of the voucher specimen; and Kodai H. Sato for providing information about related articles; Dr. Marcos Méndez and two anonymous reviewers for helpful comments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author contribution

R.F. collected and cultivated the aberrant individual; T.K.M. and R.F. observed the shoot structure; T.K.M. and Y.M. conducted the field survey; T.K.M., M.S., and J.M. discussed the developmental origin of the shoot structure; T.K.M. and Y.M. discussed the sex expression; T.K.M. analyzed the data; and T.K.M. led the writing of the manuscript.

Data availability statement

A voucher specimen of the aberrant individual was deposited at the Kurashiki Museum of Natural History, Kurashiki City, Okayama Prefecture, Japan (KURA 242667).