Why Do Prayer-Plant Leaves Lower and Rise, Day and Night? Some Theories Examine
The Marantaceae are a family of plants often referred to as ‘prayer-plants’. Interestingly, these plants move throughout a 24-hour period, with the leaves rising in the evening and lowering during the day. Resembling prayer hands, they were so aptly named for their expression of foliage folding together at night.
There are over 500 species within the prayer-plant family. The most common houseplant genus that exhibits leaf movement is Maranta, followed by Calathea, Stromanthe, and Ctenanthe. Although the family descends from African roots, these genera of plants and the species within are native to tropical and South America. Many species possess uniquely ornamental foliage with beautiful colors, lines, and shapes. In the wild, these plants are mostly found in the rainforest— which is where their fascinating survival mechanism of leaf movement was likely acquired.
Called 'nyctinasty', this term refers to the diurnal response that prayer-plants possess. As light changes, this naturally built-in indicator signals the plant that it’s daytime or nighttime. While there is no one cause that has proven concrete, the most promising theory is that the plant adapted to best capture water. As such, during the day, the plant leaves will lower or spread out to absorb moisture or catch rain. At night, this adapted behavior helps the plant retain water by folding leaves inwards— that way any water droplets can be stored as they trickle down to the plant instead of evaporating.
Another theory suggests that folding inwards at night is an evolutionary trait that increases the plant’s ability to efficiently survive. Specifically, it helps keep the plant compactly protected from predators. Although, this has been refuted by counter-theories, including that the movement of leaves might actually make the plant more susceptible to predators— specifically, because overhead birds would be more likely to see leaves moving in prayer-plants than their still counterparts.
One theory alone may not be the answer, and prayer plant movement could have multiple goals. A few other potential functions include improving the plants regulation of temperature and to prevent insects from feeding on foliage— all in order to increase survivorship.
Whatever the purpose and benefit of foliage movement, this feature of prayer-plants is mesmerizing to watch as the circadian rhythm takes over in these live beings. The fascinating display adds to the allure of these favorite indoor plants.