Scientists Solve 100-Year-Old Mystery About How Plants Took Root in Land

 

Researchers at Yale University are leading a team of experts who believe they have finally solved the long-standing puzzle of why terrestrial plants developed such intricate vascular systems.

Around 500 million years ago, when land plants first appeared, their vascular systems were quite basic.

Their roots and stems have interiors that resembled bundles of straws that would draw water and nutrients from the environment.

However, this simple mechanism for sucking in water underwent substantial alterations some 420 million years ago, progressively dividing the straws' into more complex forms, structures, and sizes.

For over a century, scientists were baffled as to why evolution favoured these more complex interiors, but a recent study of the fossil record reveals that a more contemporary vascular system may be more drought-tolerant.

 

The authors speculate that the early shaping of plant interiors may have been caused by a scarcity of water.

 

The earliest terrestrial plants on Earth were simple, moss-like organisms that were tiny. They were restricted to locations with lots of water because they lacked root systems.

The very first vascular plants were just centimetres tall and limited to the wettest environments.

One of the problems they had to solve to break out of this niche was how to keep water transport through their xylem from being blocked by embolism during drought.

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— Martin Bouda (@BoudaLab) November 10, 2022

 

Plants required new strategies for obtaining water, sunshine, and nutrients while avoiding evaporation and dehydration as they moved farther inland into increasingly dry regions.

 

Branches and roots proved useful in the situation. However, these structures also brought about new difficulties at the same time.

 

In times of drought, plants can quickly dry up and produce a vapour bubble that, like an embolism, prevents water from rising through the roots.

 

An air bubble inside a plant can easily spread to adjacent channels or "straws" in a rudimentary and primitive vascular system, blocking the flow of more water and nutrients. The outcome may possibly destroy the entire plant and cause tissue death.

 

Researchers have recently demonstrated that a more complex vascular pattern may cordon off air bubbles by modelling the diverse vascular systems of several present and ancient plants preserved in the fossil record.

 

Simulations reveal that air bubbles have fewer neighbours to propagate to when the patterns that make up a plant's vascular system are separated.

An embolism propagating in the vasculature of a basic, prehistoric plant differs from one spreading in a more complicated, contemporary plant, as shown in the video below.

 

According to plant physiologist Craig Brodersen of the Yale School of the Environment, "every time a plant deviates from that cylindrical vascular system, every time it varies just a little bit, the plant receives a reward in terms of its capacity to endure drought."

 

And if that incentive persists, plants will be forced to evolve away from the traditional cylindrical circulatory system and toward these more complicated shapes.

The woods that we see now simply wouldn't exist if plants hadn't found a way to overcome this issue very early in the history of the world.

 

Not only do the discoveries shed light on intriguing parts of Earth's past, but they also hint to potential future remedies and aid in the explanation of how the wide variety of vascular shapes seen in current plants came to be.

Researchers may someday use this new knowledge of how plants respond to drought to assist key flora be ready for the impending fast climate change.

 

Some crops may be able to feed us for a very long time in the future if scientists can find out how to breed them with superior root and vascular systems.

 

Science published the study there.