In its native habitat, the leaves of S. sanguinea are deep rich green on top and red on the underside. In cultivation, the plant has produced several remarkable variegations; these have been propagated and given cultivar names. In 2004, the Flower Council of Holland listed five'Multicolor', 'Horticolor', 'Magicstar', 'Stripestar', as well as the photographed 'Triostar' (often sold under the name 'Tricolor').
Often added to a tropical landscape, Stromanthe sanguinea nonetheless, makes a special houseplant, almost a pet houseplant. It may stand by a window, but an observant gardener will notice that it moves through the day.
Stromanthe sanguinea has both nyctinastic (night) and heliotropic (sun) movements. The movements are controlled at a pulvinus, (pl. pulvini) a swollen area near the base of the leaf blade. Two pigments are present in the pulvinus: phytochrome which is red light sensitive, and cryptochrome which is blue sensitive. Phytochrome triggers the night position of the leaves; cryptochrome triggers the day movements. Exactly how these pigments work has yet to be determined.
In the early morning, the leaf blades move perpendicular (face-on) to the incoming sunlight. This movement is diaheliotropism; it maximizes the amount of light for photosynthesis.
As the tropical sun climbs in the sky, its radiation becomes too strong. The plant cannot use the extra radiation; it only causes water loss and possibly cellular damage. The plant responds by folding the blade and moving it edge on to the incoming solar radiation. This position shelters the stomates (leaf pores) from losing too much water and minimizes solar radiation on the surface. This movement is known as paraheliotropism.
As the sun moves down toward the western horizon, the leaf blades once again move face-on to the incoming light. Heliotropism works because ions like potassium (K+) are pumped into and out of cells. Water crosses the membrane attempting to equalize the ion concentration. This creates the turgor pressures in various parts of the pulvinus that moves the leaf blade.
When the sun sets, the ion pumping ceases. The leaf blades move vertically, but are not foldedthe leaf blades facing each other create the 'praying hands' appearance. The unfolded leaf blades can freely exchange oxygen and carbon dioxide with the atmosphere and since humidity is higher at night, the plant does not lose as much water during the exchange. Through all these movements, only the leaf blades change positions, the petioles (the leaf stems) do not move.
(Compiled from: "Stromanthe", Hortus Third, Staff L.H. Bailey Hortorium, NY State College of Agriculture and Life Sciences, Cornell University, Macmillan, 1976; "Chapter 25: External Factors and Plant Growth", Biology of Plants, P. Raven, R. Evert, and S. Eichhorn, 4th Edition, Worth Publishers, 1986; and "Bio-Inspired Design of Intelligent Materials", Minoru Taya, Director, Center for Intelligent Materials and Systems, Department of Mechanical Engineering, University of Washington, Seattle, no date on article)