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Why do dew drops do what they do on leaves?

Date:
January 12, 2012
Source:
American Chemical Society
Summary:
Nobel laureate poet Rabindranath Tagore once wrote, "Let your life lightly dance on the edges of time like dew on the tip of a leaf." Now, a new study is finally offering an explanation for why small dew drops do as Tagore advised and form on the tips, rather than the flat surfaces, of leaves.
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Nobel laureate poet Rabindranath Tagore once wrote, "Let your life lightly dance on the edges of time like dew on the tip of a leaf."
Credit: © yellowj / Fotolia

Nobel laureate poet Rabindranath Tagore once wrote, "Let your life lightly dance on the edges of time like dew on the tip of a leaf." Now, a new study is finally offering an explanation for why small dew drops do as Tagore advised and form on the tips, rather than the flat surfaces, of leaves. It appears in ACS' journal Langmuir.

In the study, Martin E. R. Shanahan observes that drops of water have a preference for exactly where they collect on leaves as their surfaces cool in the morning and afternoon. Those droplets, which condense from water vapor -- moisture -- in the air, collect randomly across the surfaces of flat leaves. However, dew drops tend to accumulate at the tips of spindly leaves, even if that means defying gravity by moving upwards. He explains that an inherent "unwillingness" or "lack of necessity" of water drops to move on a dry surface governs their positioning on flat leaves, causing them to stay where they form. Dew's tendency to head to the end of finely pointed leaves, however, sent Shanahan looking for a different explanation.

The answer is based on the fundamental principle of free energy, that everything in nature seeks the lowest possible energy state. Shanahan modeled two types of dew drops on a theoretical (simplified) cone-shaped leaf: a thin, cylindrical sheath of water and a spherical drop centered on the cone's axis. In both cases, he found that the drop lowered its energy by moving toward the point of the leaf.


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The above post is reprinted from materials provided by American Chemical Society. Note: Materials may be edited for content and length.


Journal Reference:

  1. Martin E. R. Shanahan. On the Behavior of Dew Drops. Langmuir, 2011; 27 (24): 14919 DOI: 10.1021/la203316k

Cite This Page:

American Chemical Society. "Why do dew drops do what they do on leaves?." ScienceDaily. ScienceDaily, 12 January 2012. <www.sciencedaily.com/releases/2012/01/120111134041.htm>.
American Chemical Society. (2012, January 12). Why do dew drops do what they do on leaves?. ScienceDaily. Retrieved July 1, 2015 from www.sciencedaily.com/releases/2012/01/120111134041.htm
American Chemical Society. "Why do dew drops do what they do on leaves?." ScienceDaily. www.sciencedaily.com/releases/2012/01/120111134041.htm (accessed July 1, 2015).

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