Why Can Ivy Climb Up Tall Walls?
Ivy is a very common garden plant, and its most distinctive feature is its excellent ability to climb. This is because its branches grow many "little feet", just like the suction cups on the limbs of geckos. As long as it encounters a house wall, no matter how high or smooth it is, it can take "firm steps" and climb up bit by bit. It can even cover the walls of dozens of meters-high buildings with its vines, and even in strong winds and heavy rains, it will not fall down.
In botany, the "little feet" of ivy are called suction cups, which have super-strong adhesive capabilities. According to measurements, their adhesive force can reach more than 2 million times the weight of the suction cup itself! Why is the adhesive force of ivy's suction cups so powerful? Scientists used scanning electron microscopes to observe the suction cups of ivy and found that they have many extremely fine microtubes and micropores, and there are shared wall surfaces between the micropores. If they were enlarged, the connections between the microtubes would be like a complex highway network in a big city, which is truly a miracle created by nature! Based on the discovery of spongy micropores, microtubes, and folded micropore and microtube walls, Chinese scientists proposed the hypothesis that most of the growth hormones secreted by the suction cups of ivy are weakly acidic substances. When ivy climbs up and grows, once the suction cup encounters the wall, a slow chemical reaction begins, enhancing the adhesive force between the suction cup and the substrate, allowing the suction cup to "anchor" to the wall. In addition, as the suction cup grows and develops, the tendrils at the tip are constantly stimulated by contact, and secretions are continuously produced. This results in some air being "encapsulated" in the suction cup. During the growth and development process, the oxygen encapsulated in the suction cup is consumed, leading to a negative pressure inside the suction cup, which in turn creates the adhesive force between the suction cup and the wall.
The super-strong suction power of ivy's "little feet" has inspired scientists' imagination. Based on the ingenious structure of ivy's suction cups, it is possible to design and synthesize some excellent artificial adhesives. These adhesives with reversible physiological effects can not only be used in biomedicine, but also their reversible conductivity can be applied in bionics and biomolecular electronics. In addition, in-depth research on ivy can further understand the secretion, accumulation, transmission, and metabolism of plant hormones, and even potentially open up a new field for exploring the application of nanotechnology in biological heredity and evolution.