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.

摘要

天南星属（天南星科）可以随着植物大小的增加而改变雄性和雌性之间的性别表达（顺序雌雄同体）。由于大多数天南星属物种每个个体只有一个花序，因此性别表达似乎是在个体水平上决定的。然而，偶尔也会观察到雄性和雌性花序的畸形。不幸的是，由于缺乏芽结构的详细描述，它们的发育起源尚不清楚。为了估计南星的性别决定单位，我们观察了南星南星异常个体的形态。(Thunberg) 肖特有多个花序三年。第二年，异常个体产生纯雄性和雌性花序。根据这种畸形的叶序模式，我们估计花序是由于顶端分生组织通过成束而扩大而重复的。与之前报道的其他具有多个花序的天南星植物相反，异常个体的球茎在三年的生长季节后没有自发细分或分枝。因此，重复的花序可能共享资源供应，而在性别决定过程中没有生理分配。这些结果意味着性别表达是在花序水平上决定的，而不是在雌雄异体南天星的个体或小花水平上决定的。