Why do dew drops do what they do on leaves?

Jan 11, 2012

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 have a preference for exactly where they collect on leaves as their surfaces cool in the morning and afternoon. Those , which condense from — 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.

Explore further: Producing biodegradable plastic just got cheaper and greener

More information: On the Behavior of Dew Drops, Langmuir, 2011, 27 (24), pp 14919–14922. DOI: 10.1021/la203316k

Abstract
It may be observed that, when dew drops form, although they may be positioned randomly on flat leaves, they tend to accumulate at the pointed ends of thin, slightly conical growths. We discuss here the basic physics leading to this phenomenon.

Related Stories

Can a drop of water cause sunburn or fire?

Jan 11, 2010

To the gardening world it may have always been considered a fact, but science has never proved the widely held belief that watering your garden in the midday sun can lead to burnt plants. Now a study into sunlit water droplets, ...

Being small has its advantages, if you are a leaf

Jul 06, 2011

(PhysOrg.com) -- The size of leaves can vary by a factor of 1,000 across plant species, but until now, the reason why has remained a mystery. A new study by an international team of scientists led by UCLA ...

Recommended for you

Aluminum clusters shut down molecular fuel factory

18 hours ago

Despite decades of industrial use, the exact chemical transformations occurring within zeolites, a common material used in the conversion of oil to gasoline, remain poorly understood. Now scientists have ...

New catalyst does more with less platinum

19 hours ago

Platinum is a highly reactive and in-demand catalyst across the chemical and energy industries, but a team of University of Wisconsin-Madison and Georgia Institute of Technology scientists could reduce the ...

Learning from biology to accelerate discovery

22 hours ago

A spider's web is one of the most intricate constructions in nature, but its precious silk has more than one use. Silk threads can be used as draglines, guidelines, anchors, pheromonal trails, nest lining, ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.