Commelinaceae

Lore & Background

Plants in the Commelinaceae are usually perennials, though a smaller number are annuals. They are always terrestrial except for plants in the genus Cochliostema, which are epiphytes. The stems are generally well-developed and often swollen at the nodes. Leaves form closed sheaths at their bases that surround the stem, and the leaf blades are simple and entire, often succulent. The way leaves unfurl from bud—termed involute—is a distinctive feature of the family. Inflorescences occur as terminal shoots or as terminal and axillary shoots, and are classed as a thyrse made up of cincinni. Flowers are often short-lived, lasting a day or less, and lack nectar, offering only pollen as a reward. Most species are hermaphroditic or andromonoecious. Flowers tend to deceive pollinators by appearing to offer a larger reward than is present, using adaptations such as yellow hairs or broad anther connectives that mimic pollen. The family has always been recognized by most taxonomists. The APG III system of 2009 (unchanged from the APG system of 1998) assigns it to the order Commelinales in the clade commelinids in the monocots. The Commelinaceae is a well-supported monophyletic group according to the analysis of Burns et al.

Reader's Guide

Its morphological diversity, particularly in flower and inflorescence structure, is exceptionally high among flowering plants. Many species are cultivated as ornamentals. The family is notable for its ephemeral flowers that lack nectar and rely on pollen as the sole reward for pollinators, often employing deceptive strategies such as staminodes that mimic fertile stamens. The family's phylogenetic relationships are well supported by molecular data, and its classification has been consistently recognized by taxonomists, including in the APG III system. The variation in floral morphology, including differences in symmetry, stamen number, and timing of flower opening, contributes to reproductive isolation among species. The family's distribution spans both Old World and New World tropics, with some genera present in both regions.

Did You Know?

• The flowers of Commelinaceae are ephemeral, lasting a day or less, and lack nectar, offering only pollen as a reward.
• Plants in the genus Cochliostema are epiphytes, while all other Commelinaceae are terrestrial.
• Some species exhibit differential opening times for male and bisexual flowers, which may help isolate species reproductively.
• The leaves of Commelinaceae typically unfurl from bud in a distinctive manner called involute, with margins rolled in at the base.