Producing flowers is a costly endeavor for plants. They require a lot of resources and give nothing back in the way of photosynthesis. The showier the flower, the greater the investment. It should be no shock then that some plants utilize more energy efficient strategies for attracting pollinators. One of the more interesting ways in which a plant has evolved to save energy on flowering comes from a rather surprising family.
Gesneriads are known for their showy flowers. There are many variations on the theme but most are rather colorful and tubular. However, in the jungles of Central and South America grows two species of Columnea that make such generalizations a waste of time. The flowers of C. consanguinea and C. florida are small, drab affairs, especially for a Columnea. They arise from the stem at the base of the leaves and would largely go unnoticed without close inspection. It is amazing that anything could find them among the chaos of the jungle understory let alone pollinate them. That is where the leaves come in.
Towards the tip of the long, blade-like leaves are heart shaped red spots. They are translucent and to stand below one conjures a mental image of stained glass windows. Against the background of greens, these spots really stand out. Their purpose is to attract pollinators, specifically the green-crowned brilliant hummingbird (Heliodoxa jacula), which can then locate the nectar-rich flowers, pollinating them as they feed. By producing these translucent red spots on their leaves, these plants are able to save a lot of energy. Leaves are retained for much longer than flowers are and, of course, they photosynthesize.
Photo Credit: Jardín Botánico Nacional, Viña del Mar, Chile (http://bit.ly/1CXtToh) and alex monro (http://bit.ly/1uVwf0x)