I picked up a leaf.

It was a first thing I got my hands upon, I just somehow looked at it and involuntarily took it.

It was rough and fragile, yellowish, as leaves are in autumn. I smiled, admiring its beauty for a moment. Supposedly it’d be easy to draw, just a green stain of the right shape. A few crafty tricks, good brushes and you can create easy to recognize leaves. But if you dive into details, you could probably keep trying to capture its subtle net of veins and ragged edges for months. More than one art student probably exercised on still life… I wonder what kinds of ‘leafy’ effects can be created with which paints. For example, when they bend downwards, or when moved by the wind, or when having several colours at once in autumn. Has anyone captured a branch with leaves on a strong wind, or at least a single leaf, so that it really looks life-like and moving?

I ran my fingers over its surface, sensing the thickness and irregular lines. These are phloem and xylem fibres, indeed ‘veins’, conducting water and sweet saps. How do they do it? There’s no heart anywhere, pumping the fluid with muscle strength. It has something to do with the pressure differences, quite a few of them. When the water vaporizes from the leaves, it sort of pulls the water still in the tubes. And the saps, sugars? It must be connected to the concentration difference between places where there’s much and little of them. By the way, is the vein layout random, roughly determined by the growth of the leaf itself, or precisely determined, and two leaves growing in identical conditions would be identical?

A botanist, or at least a gardener, could probably assess, with his skilful glance, if this little dark spot tells something bad about the tree’s health. Or perhaps it’s starting to rot? Actually, why do leaves go dark when they rot? They are green thanks to the chlorophyll, which as a matter of fact explains nothing when you think about it, and when it breaks up in dying leaves in autumn, other dyes begin to show. How many of them are there, actually?

I looked at the greenness of the leaf, almost completely replaced by the yellow. Chlorophyll is also a wonderful construct, who would invent something like this? Like a multi-atom clamp with a large metallic atom in the centre. The best fact is that haem, which is a cause of the red hue of blood, is so very similar! How come those specific structures are so intensely colourful? Is the principle similar to colourful coordination complexes, like iron rhodanide? Or maybe it has something to do with the cloud of electrons in those molecules. I could use an imagination flexible enough to picture it.

I thought about everything what took place in the thin space between the top and bottom of the leaf. Photosynthesis is an awesome thing! It changed our planet unbelievably. It originated all the oxygen in the atmosphere after all, and it in turn supports life of all the aerobic organisms. How would the Earth look like if by some chance photosynthesis never had emerged? It would be void, nothing but sand, rocks, and seas all over the place. Only anaerobic bacteria would be alive, but anaerobic respiration has small efficiency. That’s why they had never conquered the world like thousands of billions of oxygen-breathing organisms. Everything thanks to vast numbers of plantlike primeval bacteria, which reproduced freely for hundreds of millions of years and produced the life-giving oxygen. Or perhaps larger algae also had their part in this? But did they exist already in the times when oxygen was scarce?

The base of the leaf was not entirely dry yet, it apparently has just fallen off from a tree. A tree… came into existence thanks to a marvellous invention called a branch. There are thousands of different plant forms, but they could all be described as ‘it has something like a trunk and twigs’. Branching out opens up such incredible possibilities. It introduced variety in the plant world, and the first ones to have it were lycophytes, or maybe bryophytes even earlier? It probably has been ‘invented’ several times, as there are several types of it.

You could immediately tell it is autumn by the colours of the leaf. How come plants react to days shortening and lower temperatures to shed their foliage? Do they react in some spots and then send an information all over? They do have their own hormones. Maybe the leaves themselves have some light sensitive substances which release some sort of signal to the sieve tube elements, for instance. That’s a primitive visual sense! Or maybe that’s not the case and simply shorter span of photosynthesis is decisive, because of the shorter daylight?

The leaf was drying out, it was a little brittle on the right side. Rubbing my fingers by it, I felt the fine, characteristic roughness. It is almost entirely cellulose, as is most of any plant. An incredible composite. Polymeric, parallel fibres maybe half a nanometre thick, twisted together. How are they twisted? Into some bunches or what? In a bigger scale, they build up cell walls, which add up, cell to a cell, into whole leaves, branches, trunks. And despite cellulose being a basis of all that, there are flexible twigs, hard bark, gentle leaves. Multi-tone trees are supported with bases made out of sugar.

Leaf, I thought. A funny little word. I remembered some puns with it. ‘Take it or leaf it’, ‘it leaves a bad taste in your mouth’. Just a silly play, but an English philologist could passionately write a very professional article about the origin and evolution of the word ‘leaf’. It must be very old, after all, even ten thousand years ago people needed to name it somehow.

I let it out of my hand, letting my thoughts fly away with it. Spinning around on the wind, it fell on a stone on a path.

So, I picked up a stone.

You know what happened next?

Categories: Life