Developmental Patterns of Cleistogamy and Chasmogamy in Triodanis perfoliata

Abstract

Some plants exhibit mixed mating, in which individual plants utilize both cross and self-fertilization. Dimorphic cleistogamy is one form of mixed mating. In plants that display dimorphic cleistogamy, both chasmogamous (CH) and cleistogamous (CL) flowers may occur on the same individual. CH flowers are typical open flowers that are predominantly cross-fertilized. CL flowers are closed, lack petals, and are obligate self-fertilizing. Benefits of cross-fertilizing CH flowers are that the resulting offspring may have a high level of fitness; however, they have a high energetic cost, and the flowers rely on pollinators. In CL flowers, the ability to self-fertilize may benefit plants in that reproduction can occur without the need to find a separate mating partner. However, self-fertilization generates populations that have little genetic variation and results in higher levels of inbreeding depression. Although the fitness advantages of both flower types have been hypothesized, the factors that maintain this mixed strategy have not been fully explained. Triodanis perfoliata is a local annual plant that exhibits dimorphic cleistogamy. Observing the patterns of CH and CL flowers in Triodanis perfoliata may provide clarity to how a mixed mating strategy can be maintained. In a growth room study, individual flowers were observed to compare rates of development of the two flower types. Individual plants were observed weekly to determine the spatial and temporal development of CH and CL flowers throughout the lifespan of a plant. By sequentially numbering the nodes on the main spike of the plants, the type and developmental stage of each flower at the individual node was observed. Characterizing the spatial and temporal patterns of development of CH and CL flowers in Triodanis perfoliata may provide insight to the adaptive value of dimorphic cleistogamy.