Howdy, friends! I’ve got roughly two hours before my plant biology test, and I’ve returned to write a brief intro to my test material for your enjoyment (or lack thereof). This post won’t be long and complicated, but it will answer Sapphire’s constantly-reiterated question of, “Why the heck would you choose to study plants?” It’ll also give you some background to better understand the post that logically comes after this, Plant Growth.
Plants are pretty much the most underappreciated thing on the planet, if you exclude phytoplankton and like… bees. They’re all around us, photosynthesizing, using the CO2 we dump into the atmosphere (by respiring and burning fossil fuels), turning it into sugar using sunlight, and pretty much just being chemical plants for materials that we literally would die without.
Do you like to eat? Well, in case you weren’t already aware, literally all of the energy we get started in—you guessed it—plants. The existence of Kingdom Animalia depends on plants taking energy from light and turning it into sugar.
Do you like clothing? Yup, you can thank plants for anything cotton on your person.
Do you like shelter? Yeah, wood is a thing. And it comes from plants.
Do you like medicine? Go hug a tree. (Specifically a willow tree, if you’re fond of aspirin.) Before we started making and modifiying medicines in pharmaceutical labs, most of them came from plants.
It doesn’t stop there, either. Plants are sources of lots of other molecules we use every day that we don’t generally think of as drugs (vanillin, caffeine). They clean CO2 out of our atmosphere (although we’re moving faster than they can, at this point…). It was with plants that we discovered genetics (Mendel’s peas, anyone?), viruses, and oh yeah, cells.
Just as our past and present are dependent upon plants, so is our future. Malnutrition, which affects billions of people globally, might be remedied with crops genetically modified to contain supplementary vitamins. (Golden rice was already implemented to treat Vitamin A deficiency, and it worked—it worked astoundingly well.) GMOs ([police sirens], yes, I know) are also the most viable response to the problem of growing global population and decreased crop yield due to climate change. Some scientists are even considering engineering edible vaccines from plants—can you imagine getting pertussis immunity by eating a banana instead of getting a shot?
Even if you’re one of those people who doesn’t think climate change is a problem or that vaccines are anything to celebrate (I’m not judging you), plant research is promising in other fields. Biofuels, for example, could become a renewable energy source that replace fossil fuels. Plant diseases can be treated and eradicated, which is, of course, good for crop yields. And, of course, plants are still a premium source for therapeutic drugs.
All in all, plants are basically the greatest thing to happen to planet Earth (unless, of course, you were an anaerobic organism that was alive when photosynthesis came on the scene), and we should study them. So, let’s get on that! And what better way to learn about something than through its anatomy, amirite?
We’re just going to talk about vascular plants right now, because there’s a heck-ton (that’s an English unit) of diversity in Plantae, and we quite frankly don’t have the time. Vascular plants are already complicated enough, so let’s just… stick to that.
Plants have two parts, essentially—a shoot system, and a root system. The shoot system is everything that’s above ground. The root system is—you guessed it—everything underground.
There are three types of tissues in plants—ground tissue, vascular tissue, and dermal tissue. We’ll talk about them in that order, an order which has nothing to do with complexity.
Ground tissue is… everything that isn’t vascular or dermal tissue. It’s a simple tissue type (made of one cell type), and can be made of one of three kinds of cells: parenchyma, collenchyma, or schlerynchyma. Parenchyma is thin-walled and alive at maturity (certain kinds, chlorenchyma, contain chloryphyll). Collenchyma is thick-walled and alive at maturity (it’s the mechanical tissues under the epidermis in herbaceous plants). Schlerenchyma is thick-walled and dead at maturity—it comes as fibers (flax) and schlerids (stone cells).
Vascular tissues are the most complex—all contian multiple cell types. Xylem, which conducts water through the plant like a pipeline, is made of of tracheary elements, which are essentially the hollow corpses of cells lined up to make pipes. Parenchyma and schlerenchymatic fibers are also present. Phloem, which is alive, conducts sugars, water, and hormones (sap) through the plant using living sieve-tube elements.
The vascular tissues in plants—xylem and phloem—are aranged differently in each plant part. In the root system, they form the core of the root. In the stem, they’re present in bundles, and these bundles are arranged in rings (unless you’re a gymnosperm, in which case, [vague shrugging motion]). In the leaves, they’re present as the veins that we can all see very clearly.
The dermal tissue, of course, does exactly what you’d think—it forms the “skin,” or epidermis, of plants. It also includes the periderm, the living part of tree bark.
And that’s it, folks! I realize that this post is disjointed, and I apologize for that, but I have to get going, sooo… In the meantime, enjoy this nice weather we’re having (haha), and maybe eat some vegetables for lunch? Just so they feel appreciated.
Supposedly, you might see a random post on inflammation and drugs in the future. If you do, don’t look at me…