It is no secret I love houseplants. I do. Always have. In my younger years, I used to have quite the collection, but I made a terrible mistake starting out: I thought all plants liked exactly the same things. Lots of water. Lots of light. And me, serenading them with my violin music. Besides the violin, which – I can’t comment on that– I can tell you that treating all the plants with lots of light and lots of water was a mistake. Maybe some of them liked it. But a lot of them did not. Why? You know how there are many different types of animals----well there are many different types of plants as well. They don’t all require the exact same amount of light and the same amount of water. There is so much diversity in plants – there are over 300,000 estimated species of plants – and there are some fascinating adaptations that have helped them live in a variety of environments. This video is going to briefly touch on types of plants, their structure, and some fascinating adaptations. First, we need to outline two general plant categories. Vascular and nonvascular. Recall that in the human body, your vascular system includes arteries. Well plants don’t have arteries…or blood… for that matter. When we’re talking about a vascular system in plants, we’re talking about two major types of tubes---or vessels--- called the xylem and phloem. The xylem carries water. Xylem is found throughout a vascular plant---water is absorbed from the roots of vascular plants and carried upwards. Roots help anchor plants and also to absorb the water found in the soil that they are in. The xylem continues up from the roots through the stem to the leaves. Structure-wise, the stem has a function of providing support to the leaves. Now the other vascular tissue: the phloem. So recall that glucose - a sugar- is typically produced in the leaves during photosynthesis. All the plant’s cells will need sugar. Sugaris the plant’s food source. The phloem carries sugar from the leaves where it’s generally made throughout the plant. By the way, the word phloem might start with a p but it does have the same “f” sound that food has so it helps me remember that it carries the plant’s food. If a plant is nonvascular, it does not have vessels like the xylem and phloem. However, it still needs water and it still produces sugar. It can’t carry water upwards in the xylem because it doesn’t have one. That means, nonvascular plants typically are limited in size. A giant tree needs a xylem for water transport; the water is being carried against gravity. Nonvascular plants instead get their water by osmosis. Kind of like soaking up water like a sponge. Nonvascular plants are often informally called bryophytes. I say informally because it’s kind of like when you use the informal word “protists” – the term “bryophytes” is often a collective informal term that includes three different phyla: a phylum that contains liverworts, a phylum that contains hornworts, and a phylum that contains mosses. And actually the phylum that includes mosses is a phylum called Bryophyta so again just be aware of the informal use of the word bryophytes. As they’re nonvascular - bryophytes are generally small and are more frequently - but not always- found in areas where there is a lot of moisture. They do not have true stems nor true leaves nor true roots, although they can have structures that resemble them. Now, let’s briefly discuss vascular plants – again, vascular plants have xylem and phloem. These plants also have true stems, leaves, and roots. We can arrange vascular plants into three general categories. 1. Seedless vascular plants –as their name suggests – they have no seeds. This group includes a phylum that contains lycophytes- like club mosses – which are different than the moss in the bryophytes. And it includes a phylum that contains monilophytes – like ferns. 2. Gymnosperms – these include several phyla: one phylum that has Ginkgo, one phylum that has cycads, one phylum that has gnetophytes, and one phylum that has conifers. The word gymnosperm means “naked seed” as they don’t have their seeds enclosed like the next group we’ll get to– instead, many gymnosperms have cones. Gymnosperms have neither flowers nor fruit. 3. Angiosperms – these are the flowering plants. They have flowers. They have fruit, though not necessarily an edible fruit. This is a huge group- it’s estimated that around 90% of all plants are angiosperms. Within the angiosperm group, many angiosperms – but not all - can be categorized as a monocot or eudicot. You’ll see some of the characteristics we included of these two groups in our illustrations here but just know, there are some exceptions. Overall, just trying to really emphasize: the angiosperm group is the largest, most diverse group of plants. Even though every plant species is unique, let’s talk about general plant structure. The structure of plants is critical for plants to be able to perform photosynthesis. Photosynthesis is the ability to make sugar---the plant’s own food source---from sunlight, and it requires three main “ingredients:” water, carbon dioxide, and light. To get all three of these things, the plant needs specific structures and adaptations, which we’re going to walk through. First – water. We mentioned already how a plant can obtain it in different ways depending on whether they’re vascular or nonvascular. Next, carbon dioxide. Many plants have these fascinating little openings—pores really---called “stomata” or singular, stoma. Stomata are typically – but not always- found on the bottom of leaves. Stomata have a major role in gas exchange, because gases can travel through them. And a gas plants need directly for photosynthesis is carbon dioxide. But don’t forget when it comes to gases: plants also do cellular respiration and to do that, they also need the gas oxygen. However, plants generally produce more oxygen in photosynthesis than they need in cellular respiration. Now while gases can flow in through these stomata, there’s still a little problem. Plants can’t keep those stomata open all the time. When they’re open, water can escape. And remember, plants need water too for photosynthesis. So the plant has to determine whether to open or close its stomata, and it does this with the help of guard cells. If guard cells have the stomata open, the plant gets the gases it needs but it can lose water. If guard cells have the stomata closed, it gets to save its water but then it limits gas exchange. At night, many plants – with a few exceptions- close their stomata so that they can conserve their water as they aren’t doing photosynthesis at night. Last on the list that plants need to capture is light. Plant cells have organelles called chloroplasts. These amazing organelles are not found in animal cells. They are the site of photosynthesis so they help capture light energy for the process of photosynthesis. Plants also have pigments: chlorophyll is a major one that can absorb certain wavelengths of light like red or blue light – but plants can contain other pigments too which can expand the different wavelengths of light that they absorb. Leaf structure is really important when it comes to capturing light energy. The size and shape of leaves can be different based on where different species are found. Plants that live in areas where they must conserve water might have thin leaves so that they don’t have much surface area to lose water. Think about pine trees with their skinny pine needle leaves…or think about the plants that live in the desert. Many of these plants also have especially waxy leaf cuticles to protect against water loss through the leaves. Plants that have lots of access to water---but maybe are shaded by a lot of taller plants in a jungle---might have really broad, wide leaves so that they can soak up as much sun as possible. It’s hard to live in someone else’s shadow. Since there is plenty of water, these plants may not struggle with water loss concern and can have more leaf surface area. Now we talked about general plant structure, but obviously there are plants all over the world with unique structures and adaptions. Before we end our video, we want to conclude with some especially fascinating ones. Plants, and other organisms, use nitrogen in the building of proteins. So what happens if a plant lives where the soil is low in nitrogen? You may have heard of carnivorous plants like the Venus fly trap or the pitcher plant. These plants still do photosynthesis to make their sugar, but carnivorous plants also have the ability to digest insects typically by using special enzymes in a juice they secrete. Insects are a great way to supplement this nitrogen need. If you ever look at the ingredients in plant fertilizer, you will find many fertilizers are high in nitrogen. You can also have too much of a usually good thing. What about plants that live where it’s TOO wet? Many types of mangrove trees live in waterlogged soil. These plants can have specialized roots that help them deal with the low oxygen and potentially high salt concentrations in a variety of ways – see our recommended reading. Plants can even turn into thieves to get the nutrients they need. You’ve heard of mistletoe? Is it terribly ironic that they can be parasitic as they can use their specialized roots to steal nutrients and water from a host plant? There are a ton of plant structures and adaptations we encourage you to explore. And don’t forget about the value of learning about plants. After all, plants are essential for life---they are producers which means that they are the main support for food webs. Many medications that we have today are derived from plants. And while plants aren’t the only photosynthetic organisms, plants are definitely known for their photosynthesis which produces oxygen for us to breathe by the photosynthesis that they do. Explore more about plants with our Shorts on plant tropisms and plant hormones and our entire video on plant reproduction and the structures involved! Well, that’s it for the Amoeba Sisters, and we remind you to stay curious.