Babbling Science’s Beauty (BSB)

Rainwater drop onto a leaf, and life evolves as we know it

My front yard small garden / Credit: author

Quick disclosure: Please be aware that this article is a simple and humble attempt to describe the beauty of nature using terminology and shared knowledge. I am throwing the old BSB again because science is poetry, even if complexity may stretch out from our imagination a bit (just a bit, though).

Transported by precipitation clouds, the extra water is not scarce but a result of life on earth. The reaction of gases turns liquid into reality, making rainfall from the sky, landing where it is most appropriate. Grass, dirt, building, mouth, face and asphalt; we cannot forget leaf.

The subtle drop pushes the leaf hairs down flat. Sensory signs send chemical messages to the whole structure. The raindrop runs down the lamina if smooth, glued to the blade. It encounters many veins, avenues full of chlorophyll on the way to the margins. These avenues diverge the drop depending on the depth, friction and direction.

Photo by Clay Banks on Unsplash

It may move straight down, bending the leaf in half. Or it may slide sideways, only tilting the leaf backward like a slap in the face. It could even land perfectly in the middle near the axillary gland, connecting the blade and petiole, travelling down the same path until arriving at a node. The node is connected to the main stem, where many nodes go up and down. The in-between nodes, including all twig nodes, are named internodes.

Internodes may determine growth per year, showing how many nodes were produced thanks to a mix of hormones and tropism, lengthening the whole stem. The raindrop continues to travel down the branch, finding obstacles on the way. The bark texture, fissures, and grooves are only standard vertical “micro-mountains” that the liquid may find appropriate to accumulate and moist. Lichens, mosses and microbes are the living beings usually found in these bark crevices other than insects.

A mix of algae and fungi (not long ago discovered to be ménage à trois: ascomycete, basidiomycete and green algae), lichens still photosynthesise but rely on enzymes to break down organic matter: an exciting relationship yet mysterious to many scientists. Given the life of these tiny living organisms, the raindrop doesn’t halt at any moment. It voyages down the stem, aiming to the ground where gravity seems to be the major inevitable push. A few steps from hitting the surface, the raindrop is ready to reward all living beings below the tree crown.

Lichen and moss sharing same bark crevice / Credit: author

After many fine wet droplets fall from the sky, the soil becomes moist, allowing micropores and macropores to accommodate themselves. Water and air must follow freely through the ground, giving more chances of absorption for the plant root by osmosis. Root hairs and caps are specialised organs that extract essential minerals from the water. Without them, the plant wouldn’t be able to survive.

At the same time, touching upon root osmosis, some plants would be nothing without mycorrhizal fungi. A word meaning “root and fungus”, the central part named mycelium stretches thin white fork-like filaments after connecting to the root system, reaching a much larger area than the root could do itself. The fungus assists the rhizome in absorbing essential minerals and nutrients, while roots give carbon and carbohydrates back to the fungus, creating symbiosis.

White fork filaments of mycelium / Credit: author

Some may consider this a coevolution, but it is more like a coexistence resulting in companionship. Still, we know that the fungi have existed much longer than trees, so fungi might have taken some advantage once they developed complex systems to help trees survive the myriad sea of possibilities.

It is difficult for us to imagine how plants feed themselves. Plants are autotrophs and osmotrophic, meaning they produce their food by water, air and sunlight — an outstanding achievement for starters. As many professionals say, plants are self-optimising mechanical structures.

For the roots to absorb nutrients and minerals sufficiently, they also use osmosis, where only small particles can pass through the cell walls membrane. As mentioned previously, organic matter and minerals need aid from fungi and bacteria to break down elements so the plant can absorb them easily.

This description of life (leading to death, then life again) simply shows a collective effort, starting from a raindrop touching the ground among different organisms. All of them cooperate in pledging life on this planet. Without one of them, the earth wouldn’t support such high biodiversity.

In short, animals feed on plants that provide organic matter for microorganisms that feed on carbon that assist other plants that grow from water and other gases — this is our crucial life cycle; it is up to us to understand how and why it happens. It shows that we can only respect and follow suit for our survival as sole consumers, but it must be a way to give it back. Perhaps this is the intriguing dilemma so far.

Thank you for reading!

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Tiago Miranda

Tiago Miranda

Naturalist | Arborist | Lecturer | Climber