Microscopic View of How Leaves Repel Water

An anonymous reader writes: Years of research has gone into products that are hydrophobic — they resist getting wet. But nature solved this problem long ago, and it's ubiquitous outside our buildings and homes. You've probably seen it yourself, after a light rain: water collects in round droplets on many leaves from trees and plants, refusing to spread out evenly across the surface. This article explains why that happens using super slow-mo cameras and an electron microscope. "[T]he water isn't really sitting on the surface. A superhydrophobic surface is a little like a bed of nails. The nails touch the water, but there are gaps in between them. So there's fewer points of contact, which means the surface can't tug on the water as much, and so the drop stays round. ... [After looking at a leaf in the electron microscope,] we saw this field of tiny wax needles, each needle just a few microns in length! The water drops are suspended on these ultra-microscopic wax needles, and that keeps it from wetting the surface."

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Sunlight and Water Myth

[Catamaran]

Garden Mythbusters: Does Sunlight and Water Mixing Really Burn Leaves?
Two years ago, four Hungarian scientists published a paper called “Optics of sunlit water drops on leaves: conditions under which sunburn is possible” in the journal New Phytologist. Given the near-universal belief that water drops can scorch plant leaves on a sunny day (e.g. the RHS book How To Garden: “Under a hot midday sun, water droplets on leaves will act as miniature magnifying glasses and may scorch them”), you may be surprised — or you may not — that no one had previously checked to see if this actually happens.
First of all, the short answer is no.
Are there any circumstances under which water drops on leaves can cause sunburn? Yes, but only if the leaf has a dense covering of water-repellent hairs, in which case drops can be held above the leaf surface, allowing them to focus light on the surface itself.

Re:Sunlight and Water Myth

[Charliemopps]

Garden Mythbusters: Does Sunlight and Water Mixing Really Burn Leaves?

  Two years ago, four Hungarian scientists published a paper called “Optics of sunlit water drops on leaves: conditions under which sunburn is possible” in the journal New Phytologist. Given the near-universal belief that water drops can scorch plant leaves on a sunny day (e.g. the RHS book How To Garden: “Under a hot midday sun, water droplets on leaves will act as miniature magnifying glasses and may scorch them”), you may be surprised — or you may not — that no one had previously checked to see if this actually happens.

First of all, the short answer is no.

Are there any circumstances under which water drops on leaves can cause sunburn? Yes, but only if the leaf has a dense covering of water-repellent hairs, in which case drops can be held above the leaf surface, allowing them to focus light on the surface itself.

The point is moot.
This question became a "Thing" mostly because of people growing pot in their basements. About 15yrs ago it became something you could do with nothing more than a trip to Home Depot. Unfortunately, due to draconian laws people are forced to hide this to the point the plants are usually grown in secret rooms, fake cabinents, etc... So the plant is in a very tight area, lots of humidity and questionable airflow. Because of this situation, watering became because of all the bending and manuvering to get into where-ever it was secretly grown. So water could often end up all over the place and take a long time to evaporate. The artifical lights are also very directional and high intensity compared to the sun. Average sun density outdoors is 10,000 lumens per quare meter. To achieve that inside you need lights that may have point intensities above 50,000 lumens. Outdoors the sunlight is very diffuse and spread out. Inside its only coming from one direction.

As a result people started knowing spotting on leaves. This could come from any number of things. Mold because of the humidity. Normal damage just from the water droplets. Heat from the lights. Over watering. Over fertalizing. Or possible the droplets of water were burning the leaves due to the high intensity lights.

Whatever the cause, when you have a single plant that's worth over $3000, and growing multiples just incase one gets diseased and dies puts you into felony territory because backwards laws are charged based on #s of potted plants rather than your actual situation, you tend to get concerned and its best to just not let water get on the leaves.

New iPhone 6 feature

[ArcadeMan]

The screen will be covered with tiny microscopic wax needles.

Forest, Trees, Proverbial.

[bmo]

FTFA:

Why would a plant evolve a method that cleans the under-side of its leaves?

Come on, man, THINK for a second. What *else* might stick to leaves that the plant might not want? What about fungal spores? You know, organisms that might *eat* you if you were a tree? If you thought about it for a second, deciduousness in itself is a scheme to battle fungi too.

This really is "missing the forest for the trees" or in this case, leaves.

--
BMO

Re:Forest, Trees, Proverbial.

[SpankiMonki]

If you thought about it for a second, deciduousness in itself is a scheme to battle fungi too.

I think you might be thinking too hard. Water conservation in colder climes/drought conditions is the most often mentioned advantage of flora shedding their leaves. I've never heard "battling fungi" mentioned as an advantage for "deciduousness" until now. http://en.wikipedia.org/wiki/D...

Waxy cuticle and trichomes

[solanum]

A bit of fun for those involved, but funnily enough plant science has actually investigated this over many decades. Go to a search engine of your choice and look up "waxy cuticle" and "trichomes". Sorry if I appear snide, but this is rather like someone posting an article about how they were amazed at what is inside their desktop PC, with photos and everything, as if no one had looked inside one previously. Neither the word cuticle nor the word trichome appear in that article, which shows they made no attempt to find out anything about their subject. Nice videos though, would be good for teaching!

I don't often read Wired.

[newcastlejon]

Are their articles usually written by 10 year olds?

[Janine is] a super-skilled researcher, and she also has access to some of the coolest toys in existence.

This person is supposed to be a professional writer?