While sexual reproduction is all well and good, many plants are able to reproduce asexually as well. This asexual reproduction is sometimes called vegetative reproduction, which results in genetically identical offspring or clones. One way that plants will do this is by shooting off a stem that will form a new individual. The stem will travel underground and then produce a new individual, as you see there. We call these rhizomes. Their complement, if you want to think of it that way, are stolons, which are stems that shoot off and produce new individuals above ground. So, the rhizomes are underground, and stolons are above ground. These stolons will also produce adventitious roots, which are roots that are generated from the stem. Occasionally, plants can form seeds without fertilization. This means that gametes, specifically the sperm and the egg, do not need to come together to form a seed, which we will discuss later in the lesson. We call this apomixis, so seeds forming without fertilization. This again will result in a clone or a genetically identical offspring. You can also split plants into fragments, and in some plants, these fragments will develop into mature organisms. We call this fragmentation. This is similar to the idea of making cuttings or clippings of plants to grow new individuals. While this is great in terms of efficiency, as the plants do not have to go through the hassle of sexual reproduction, it leaves them genetically vulnerable. Because they are producing genetically identical offspring, there is less genetic variation in the population, and this can have disastrous results sometimes. For example, consider bananas. Depending on how old you are, you may or may never have tasted the world's best banana because they no longer exist. Bananas are grown from clippings. They undergo fragmentation, and we plant the clippings, and that is how you get new banana trees. The problem is, they are all genetically identical. Every now and then, a fungal infection or something like that will come around and wipe out an entire population of bananas. This has actually happened more than once, and that is why the bananas we have today are not nearly as good as the varieties that we used to have decades ago, which have disappeared due to unfortunate circumstances. I like to think of this as the tragedy of the banana. Vegetative reproduction with human involvement, like with those bananas, will be called vegetative propagation. This involves making cuttings, and using these cuttings to grow new organisms. Those cuttings will be able to produce roots because they will have a callus at the wound site. Remember, that is going to be a mass of cells that are able to differentiate and develop into mature cells, and they will be able to produce roots from the site of injury. With that, let's move on from asexual reproduction to the reproductive structures of angiosperms, which are flowers. These flowers produce gametes, embryos, fruits, and seeds. But first, a little flower terminology. Sepals, as you can see in this image, are green leaf-like things that serve as protection for the flower buds. So when you see the flower bud initially, it is completely covered by the sepals. Then, the flower petals will pop out of that. Generally speaking, sepals are green, but not always. When you take all the sepals together, for example in this image, we have five sepals here. All of those taken together, including the green cup-like structure that the sepals connect to, is called the calyx. Petals are modified leaves that surround the reproductive parts of the flower and are usually there to attract pollinators. Just like the calyx is the entire group of sepals, the corolla is the entire group of petals. With that, let's flip the page.
36. Plant Reproduction
Flowers
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