Advances in cleistogamy of angiosperms

Cleistogamy (CL), a breeding system in which permanently closed and self-pollinated flowers are produced, has received increasing attention in recent years. The present study summarised the different types of cleistogamy, the variation of floral organs, their distribution in angiosperms, phylogenetic evolution, and related regulatory genes. There are three types of cleistogamy: dimorphic, complete, and induced cleistogamy. Among them, the occurrence of dimorphic cleistogamy is 77.3%. Cleistogamy is present in 705 angiosperm species, distributed across 236 genera and 53 families. Compared with chasmogamy (CH), the number of floral organs in cleistogamous flowers is reduced and the lodicules are degraded. Genetic control of cleistogamy involves one to three genes. Cleistogenes songorica is a representative plant with dimorphic cleistogamy. The morphology of CH and CL flowers revealed a significant difference, and the seeds are heteromorphic. The phylogenetic tree of the genera in Poaceae indicated that the relationship between Cleistogenes and Diplachne, belonging to Tridentinae, is closer than originally presumed. Such information will provide valuable background for understanding the ecological significance and role of genes in cleistogamy.