Natures wonders: water is structure in soft plants (Introduction)

by David Turell , Monday, May 15, 2017, 18:00 (2747 days ago) @ David Turell

When a green plant (not a tree) gets limp it is because it does have enough water to fill its tubules. Trees with hard back have tough lignin to keep them upright. Both types of plants have the water come up from the roots by capillary action:

https://www.wsj.com/articles/where-does-all-the-water-go-when-you-water-a-plant-1494596625

"A plant is just an engine for turning water and carbon dioxide into oxygen and sugars, a process known as photosynthesis. But even though this mechanism defines a plant, less than 1% of the water sucked up by the roots is used in this way. The other 99% forms a slow upward fountain that starts at the roots, flows up inside the stem and then evaporates from tiny holes on the leaves. This seems tremendously wasteful until you consider the benefit: access to carbon dioxide.

"Those little holes on the leaves allow carbon dioxide in, but they also happen to let water out. During the day (when the holes, called stomata, are open), every plant we look at is sucking water upward through a thin fragile system of plumbing that ends at the leaves. This throughput of water is the sacrifice necessary to maintain the carbon-dioxide supply. But if it’s just passing through, why is the loss of water so serious?

"If I forget to water for a few days, the neglect is embarrassingly obvious to everyone. The tomatoes go first, wilting and then dramatically flopping over, triggering immediate guilt. And while I’m rushing to make it up to them with liters of aqueous elixir, the real truth of a plant is evident: The water isn’t just flowing passively through this beautiful green structure that happens to contain a photosynthesis factory. It’s holding it up.

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"the plant cells become robust little bricks when you fill them with water. A typical car tire might be filled to twice atmospheric pressure, but the pressure in a typical plant cell might be five or six atmospheres.

"It’s all about natural hydraulics. Take the water away from a small plant, and the structure flops over. This method has its limits, though—bigger plants grow a woody reinforcement, a natural polymer called lignin, which takes over the structural support. That’s why trees don’t wilt.

"This system of hydraulic architecture gives us a final twist in the tale. My plants seem fixed in shape, but they’re not. At the base of some leaves, there’s a small section of stem that can move the leaf around, either to close it at night or to track the sun. By pumping water out of the cells on the top side of this section (shrinking them) and into the cells on the underside (puffing them up), the plant can raise the leaf upward.

"That hydraulic system allows plants to move in response to their surroundings. Sunflower buds, for instance, follow the sun across the sky using these little cellular pumps. The same system also opens and closes the stomata.

***

"When you next see a little green shoot poking out from the sidewalk, spare it an extra thought. A plant isn’t just a static green object. It’s a little living factory, fueled, supported and moved by one molecule: water."

Comment At some point during the 'plant bloom' period of evolution these green plants came into existence. This water mechanism had to be there in complete form all at once for the plants to survive. Not step by step, all at once. Only full design can accomplish this result.