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Monday, April 22, 2024

Column: Strategical plants

Imagine that a fire has just devastated a small area of forest. Trees have burned to the ground, leaving stumps and cracked trunks. All of the small bushes or grasses are completely blackened.

What’s left? Tiny seeds. The healing of the forest is partially accomplished by these seeds that only germinate after a fire. When the old, dry trees burn down, the fire breaks these seeds’ dormancy and allows new, fresh trees to grow.

This example shows how plants are evolutionarily advanced organisms. Though they can’t walk around like animals can, they are capable of a great deal of strategy, as well as offensive and defensive action.

Simple defenses are common among the plant kingdom, all to make them less palatable or even deadly to their many enemies. Thorns, pricks, irritants and poisons are all to make sure that they won’t be devoured as soon as they sprout.

Except, of course, the parts they they want to be eaten.

The next time you bite into an apple, remember that what you’re eating is an ovary. The idea from the plant’s point of view is that an animal will eat the entire sweet, juicy fruit and walk a distance away before defecating out the seeds.

Seeds reach the ground with ready-made fertilizer, and the plant has successfully spread its genes.

Human-cultivated fruit has bypassed some of these evolutionary mechanisms, with worrying results. The most common type of banana is called the Cavendish banana, a seedless banana first cultivated in the 1860s. In order to propagate more trees, farmers have to carefully remove and transplant the underground stem where they want the new plant to go.

When Panama disease, a fungal infection, nearly wiped out the entire banana population of the popular Gros Michel strain, breeders scrambled to find a new type of banana that was resistant to the disease. The result was the Dwarf Cavendish, a strain chosen for its hardiness and ease of transport rather than superior taste.

Thankfully, we learned our lesson by … uh, making all of these bananas clones of each other. Well, live and learn. Researchers have learned their lesson somewhat, as they are working to make resistant hybrids that are still tasty enough for the mass market.

Some species of plant are much more resistant to being eaten, and in fact are sometimes the ones doing the eating.

Take a species of pitcher plant, Darlingtonia californica. This plant is also called the cobra lily for its almost predatory trickery. The basic strategy of the pitcher plant is to lure hapless insects inside of its container, which is full of digestive juices.

Why can’t the bug just fly out again, if they manage to get out of the deadly liquid fast enough? Well, the inside of the container is slippery, first of all. It also has clear areas, like little windows. The fly jumps up to what it thinks is an escape route, bumps against the wall and falls back into the liquid.

Rinse and repeat until the insect is dead. Plants are more diabolical than we give them credit for.

Most plants aren’t carnivorous and are just content to grow and spread their genes. This must involve some strategy as well, though. The leaves are the organs that absorb the most sunlight; if the plant grows in the deep forest and ends up covered by shade, how can they get the sunlight that they so desperately need?

They either must grow huge leaves (which is often what you’ll see in the deep underbrush of a tropical rainforest) or they must change where the leaves grow.

It’s difficult to see in real time, but if you’re able to find fast-motion growth of a plant on YouTube, find one and watch it. You’ll notice that often, the stem will grow in one direction, stop, then take a stem in a different direction. This is often because the original stem wasn’t getting enough sunlight and it just wasn’t worth the energy it would take to completely grow it.

Roots do this, too. When a plant is just starting to grow its roots, they usually spread in all directions. Soon enough, they find that one location happens to have more nutrients than another. The section of roots in the low-nutrient place will die, and the plant now has more energy to spread in the place with the highest nutrition.

So when you look at a plant, remember that you’re looking at one of nature’s most strategical organisms.

AMY STEWART can be reached at science@theaggie.org.


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