Relationship between stigma sensitivity and floral traits in three Mazus (Mazaceae) species with bilobed stigma

Three Mazus species, that is M. spicatus Vaniot, M. longipes Bonati, and M. stachydifolius (Turcz.) Maxim., in different pollination environments and with significantly different floral structures were selected in our study. By observing stigma behaviors and measuring floral traits, the relationships among them were analyzed and compared. Results indicated that under the same stimulation, M. spicatus was the least sensitive (Longest stigma closing time), followed by M. longipes, with M. stachydifolius being the most sensitive. Furthermore, the three Mazus species showed significant differences in floral traits, such as flower color, floral display, anther stigma separation, and pollen-ovule ratio. Compared to M. spicatus and M. longipes with weaker stigma sensitivity, M. stachydifolius with stronger stigma sensitivity had purple flowers, larger single flower display area, longer anther-stigma separation, and larger pollen-ovule ratio. Our study indicates that the evolution of stigma sensitivity in Mazus may be closely linked with floral traits that influence pollinator attraction, pollen loads, pollen deliver efficiency, and composition pattern of the plant mating system.