The Marantaceae are a family, the arrowroot family, of flowering plantsconsisting of 31 genera and around 530 species, defining it as one of the most species rich families in its order. Species of this family are found in lowlandtropical forests of Africa, Asia, and the Americas. The majority of the species are found in the American tropics, followed by Asian and African tropics. They are commonly called the prayer-plant family and are also known for their unique secondary pollination presentation.
Description
The plants usually have underground rhizomes or tubers. The leaves are arranged in two rows with the petioles having a sheathing base. The leaf blade is narrow or broad with pinnate veins running parallel to the midrib. The petiole may be winged, and swollen into a pulvinus at the base. The inflorescence is a spike or panicle, enclosed by spathe-like bracts. The flowers are small and often inconspicuous, irregular, and bisexual, usually with an outer three free sepals and an inner series of three petaloid-like segments, tube-like in appearance. The fruit is either fleshy or a loculicidal capsule.
Taxonomy
The APG II system, of 2003, also recognizes this family, and assigns it to the order Zingiberales in the clade commelinids in the monocots. The Marantaceae are considered the most family in this group due to the extreme reduction in both stamens and carpels. The family consists of 29 genera with about 570 known species, found in the tropical areas of the world except in Australia. The biggest concentration is in the Americas, with seven genera in Africa, and six in Asia.
Marantaceae have a distinctive pollination mechanism that is defined by an explosive style movement. It is commonly termed explosive because the action is swift, occurs only one time for each flower, and is irreversible. This quick pollination event plays a significant role in optimizing mating and has been hypothesized to be a factor in the high level of speciation within this family. There are two parts of the floral anatomy that contribute to the explosive pollination mechanism: the style and the hooded staminode. The secondary pollination presentation begins after a mechanical stimulus is introduced by a pollinator on the trigger appendage of the hooded staminode. Touching this trigger causes the release of the style from the contacted staminode, leading to rapid inward rolling of the style which is no longer being held under high tension. During this quick rolling movement, self pollen is deposited on the pollinator while cross-pollen is scooped off the pollinator into the stigmatic cavity. This single action occurs very quickly with the full movement being clocked in at around 0.03 seconds. There has been debate on the specific mechanism of style release/movement. Many wondered whether the release is initiated physiologically or biomechanically. Markus Jerominek and Regine Claßen-Bockhoff published a study in 2015 outlining their results to their artificial release experiments as well as their electrophysiological measurements on prayer plants. In their artificial release experiments, they tested both the influence of electric impulses and chloroform to investigate whether the style movement can be induced electrically or chemically. As a reference, they used the Venus flytrap and its rapid movement which is known to be initiated by electrical changes of the membrane. To test if rapid style release could be induced by electric signals, a minutien needle was attached to the style and electric impulses were given. To test if the style movement could be released physiologically, chloroform was applied to the upper surface of the style. In both artificial release experiments, the Venus flytrap movement was successfully induced but the style movement in Marantaceae was not released. This led them to conclude that the style movement is released biomechanically due to the built tension between the style and hooded staminode contact. This unique style movement of the Marantaceae secondary pollination presentation provides evidence that not all rapid plant movements are initiated by electrical changes in the membrane.
Uses
The most well-known species in the family is arrowroot, a plant of the Caribbean, grown in parts of the Caribbean, Australasia, and sub-Saharan Africa for its easily digestible starch known as arrowroot. It is grown commercially in the West Indies and tropical Americas. Several species of genus Calathea are grown as houseplants for their large ornamental leaves, which are variegated in shades of green, white, and pink. Other genera grown for houseplants includes Stromanthe, Ctenanthe, and Maranta. Calathea lutea has tough, durable leaves used to make waterproof baskets, and in the Caribbean and Central America, its leaves are used for roofing. Two Mexican species - C. macrosepala and C. violacea - have flowers that are cooked and used as vegetables. C. allouia or leren, from the West Indies and tropical America, is known as sweet corn root for its edible tuber. Schumannianthus dichotomus is used for weaving mats to use on floors and beds.
