Leaves That Look Like Abstract Maps

What would the world be without a bit of imagination? Maybe more straightforward but certainly less magical. That's why we’re going to take a near microscopic tour of leaves, that's right, ordinary green, yellow, red, orange and even purple leaves. We were wondering what they must look like to those crawling on them and, after putting ourselves in the insects' shoes, made a stunning discovery: they live like us! They have networks of highways, streets, rivers and some very orderly settlements. The leaves seem to document these and work as their maps! Very interesting indeed...

Here's an example of urban density:
Autumn leaf Photo:
Image: Fred Jacobs

And another one - that's Toronto:
Toronto city map Photo:
Image via ccablog

Orderly settlements:
Green leaf Photo:
Image: Jan Krömer

Follow the main road, take the second left and the third right. We’re the fifth settlement on the left:
Simple brown leaf Photo:
Image: Rawhead Rex

Leaf veins are the intricate and fascinating structural skeletons of leaves. They are also essential systems of nutrient and water transportation. Each vein consists of water-conducting tissue called xylem and sap-conducting tissue called phloem. They are surrounded by a protective wrapper of structural tissues. The space between the veins – a tissue called parenchyma – is packed with chloroplasts, the organelles responsible for photosynthesis.

The arrangement of the veins on a leaf is called venation. Here's a good example of a leaf with pinnate venation, meaning one mid-vein with smaller ones branching off laterally.

Always stay on the main road!
Leaf of a Mexican plant Photo:
Image: Alex

A leathery map:
Orange-brown leaf Photo:
Image: Steve Jurvetson

Agricultural fields or skunk cabbage leaf?
Photo:
Image: The Montessorian Librarian

Green indicates the suburbs, red urbanisation:
Like a cauliflower leaf Photo:
Image: Peter Shanks

Hey, Havana is a leaf!
City map of Havana Photo:
Image via cubamapa

Zoning is in effect in Poinsettia:
Euphorbia pulcherrima Photo:
Image: Kevin Dooley

Researchers have been fascinated by the patterns that leaf veins form and discovered that only one simple mechanical model may be at work in all leaves. Comparing leaf vein networks with webs of ropes and threads, in the model below, the spot where a small vein joins a large one is marked with a green arrow. The angles between the smaller and larger vein approach 90 degrees, like the angles would be when pulling on a light thread tied to a taut rope. Tree-way junctions of veins of the same size are marked with a red arrow and the angles between them have been found to be roughly 120 degrees.

Here's the rope web model:
Like a rope network Photo:
Image via aip

And here a leaf in black-and-white, quite sinister looking urban planning:
Black and white image of leaf structure Photo:
Image: worak

There are two subtypes of venation distinguished by the extension of the veins. Craspedodromous venation describes those leaves where the major veins stretch up to the margin. In camptodromous leaves, major veins extend close to the margin but bend before they intersect with it. Below is an example of a craspedodromous leaf.

We live in Victoria Amazonica - take a right where the second main road forks:
Photo:
Image: Frank Wouters