Mussaenda recurvata

Naiki, Akiyo, Tagane, Shuichiro, Toyama, Hironori, Dang, Van Son & Yahara, Tetsukazu, 2017, Mussaenda recurvata (Rubiaceae), a new species from southern Vietnam with observations on its heterostyly, Phytotaxa 328 (2), pp. 167-174 : 171-172

Heterostyly in Mussaenda recurvata

Mean values (±SD) of seven floral characters are shown in Table 1. Stigma height (SH) of long-styled flowers and anther height (AH) of short-styled flowers were significantly longer than those of the opposite type of flowers. Ovary length (OL) and diameter (OD) were significantly larger in long-styled flowers than in short-styled ones. There were no significant differences in corolla tube length (TL), corolla diameter (CD), and tube base diameter (TD).

There was little overlap between stigma height of long-styled flowers and anther height of short-styled ones, and between anther height of long-styled flowers and stigma height of short-styled ones ( Fig. 4 ).

Mussaenda recurvata is morphologically heterostylous (distylous), but at least functionally gynodioecious, as long-styled flowers are female with anthers that lack pollen grains and short-styled flowers are morphologically hermaphroditic. However, it is likely that short-styled individuals are male, as no fruit set was observed in the inflorescences of short-styled individuals. In contrast, there were several fruits seen in long-styled flowers during our field observations in November 2014. Mussaenda recurvata is considered a functionally dioecious plant, a characteristic known from some other Mussaenda species ( Naiki & Kato 1999, Li et al. 2010).

TABLE 1. Measurements of seven floral characters between flowers from long- and short-styled plants of Mussaenda recurvata in a population of the Hon Ba Nature Reserve, Khanh Hoa Province, Vietnam.

Figures

FIGURE 4: Relationship between stigma height and anther height of one flower for each individual of Mussaenda recurvata Naiki, Tagane & Yahara in a population of the Hon Ba Nature Reserve, Khanh Hoa Province, Vietnam. Circle: long-styled flowers, diamond: short-styled flowers.