Tillandsia Biology: Trichomes
Trichomes are tiny specialized appendages found on the skin of plants, similar to hairs or scales. All plants have trichomes, and they are useful for many purposes, but no plants on Earth have developed such sophisticated and versatile trichomes as xeric Tillandsias have managed to. Trichomes can be numerous and dense on a Tillandsia, few and sparse, or a combination thereof.
The shapes and layouts of trichomes on an air plant are wonderfully varied, and depend on the species. Extreme environmental stresses have caused Tillandsia trichomes to evolve into various different configurations, useful for specific purposes. Overall, Tillandsias get the greatest benefit from their trichomes in two areas: the absorption of water, and the blockage of harmful solar radiation. Typically, more trichomes stuck closely together indicates a plant from a more arid environment, and results in a silvery-looking plant.
(T. tectorum, an example of the most trichome dense air plant in existence)
The most visible part of the trichome is the ‘wing.’ The wing appears as a white or silver color because it is filled with air that reflects harmful sun radiation. When filled with water, the wing becomes clear, which is why silvery xeric Tillandsias (such as Xerographica) always look greener right after being watered. When contacted by water, a dry trichome wing will immediately suck up water via osmosis (“water will travel to where water is not”), and send it into the plant for storage. In a T. tectorum, the wings stick out, perpendicular to the plant skin, causing a fuzzy look and a rough feel. This adaptation allows the T. tectorum, which is sensitive to water, to dry quickly, as the lifted wings reveal more plant surface area. On the other hand, T. xerographica’s trichome wings lay flat, parallel to the plant’s skin, and are densely packed. This causes a smooth look and velvety feel- this configuration allows for maximum sun protection and water retention. Other species show other fascinating layouts.
(T. xerographica, another trichome-dense plant as seen by its light gray color)
Much of the scientific knowledge of Tillandsia trichomes was only discovered in the past few decades, and they remain a somewhat mysterious subject. It is certainly possible that they occupy yet unknown important roles, but even our current understanding tells us that without trichomes, Tillandsias- as we know them- wouldn't exist.
J Hamlett, A.S. Horticulture Science
Air Plant Hub Blogger