Botany for Gardeners - The Basics of Blooms
To begin learning music, one must first learn the musical scale, for it is from that scale that all music is developed. In the botany of flowers, the musical scale is the essential parts of the flower and what their function is. So let's start there, using the illustration at right as a guide. Remember that this is a very basic flower, but it still has all the parts that make up a flower with both female and male parts. Your first botanical term is the term for such a flower; it is a monoecious flower. If a flower is either male only or female only, it is known as dioecious.
Our generic flower has been cut in half to show the internal structure of the female parts. This particular flower, if whole, would have 5 petals (the pink leaflike parts), 5 sepals (the small green lobes at the base of the petals) and 5 stamens (the thin stalks with the yellow parts on the ends). The petals comprise the inner circle of floral envelopes, and this inner circle is known as the corolla. The sepals comprise the outer circle of floral envelopes, and that is known as the calyx. Plants that have flowers with either 4 or 5, or a multiple of 4 or 5, of the flower parts represent the most familiar group of flowering plants, shrubs and trees. Botanically and collectively, these plants are referred to as 'dicotyledons" or dicots, because when their seeds germinate, the newly emerged seedling has two "cotyledons", or seed leaves. Another large familiar group of flowering plants, including grasses, lilies, banana plants, and many others, are the monocots, or "monocotyledons". These have a single seed leaf, or cotyledon, and their flower parts come in 3s or multiples of 3.
Next, let's see what parts are the ones that lead to the formation of seeds. First of all, the flowering plants are known as angiosperms. What this term means is that the seeds are enclosed in an ovary, or what I like to call an ovulary because the seeds are not eggs (ova), but are ovules. What about plants that do not have their seeds enclosed in an ovary or ovulary? Those are known as gymnosperms, or "naked seeds". Two notable members of the naked seed plants are pine trees and cycads.
Ok, to make seeds we need both male cells and female cells to come together. The male cells are formed in the yellow parts at the end of the thin stalks, or filaments seen in the drawing at top, right. These yellow parts are known as anthers and they produce the male cells, known as pollen grains. The red stalklike part and the chamber below it with two white seedlike objects comprise the female part of the flower, known as the pistil. The ovary is where the two white ovules are located, and the red stalklike part is actually two parts, the stalk and the enlarged end at the tip. The stalk is known as the style and the enlarged end is the stigma, where the pollen grains come to rest and germinate. Yes, that's right, pollen grains actually germinate, but instead of producing roots and leaves, they produce a single rootlike structure, the pollen tube, that grows into and down the style to the ovaries and waiting ovules. Once the pollen tube reaches an unfertilized ovule, it penetrates and releases the pollen nucleus into the ovule, there to fuse with the ovule nucleus. After a successful fusion, a fruit with seed develops.
Variations on a theme
Now, starting with these basic parts, a mind-boggling number of different types and variations on the flower theme have manifested in the natural world. Of course, botanists have specialized terms for all of the possible different parts and modifications of those parts. Detailing all of these is beyond the scope of this brief introduction, but I will share some for illustrative purposes. The basic flower can be symmetrical like a pie cut into equal pieces, where each piece looks like the other pieces. This type of flower is known as actinomorphic, and an excellent example of such a flower is Cosmos. Another type of flower is symmetrical only if cut in half along one plane; this type of symmetry is known as bilateral symmetry, much like our own human bodies are, and this type of flower is known as zygomorphic. The flower of the pea plant is this type of flower. Some flowers have the ovary located just above the petals; these flowers are said to have a superior ovary. This does not mean it is better than other ovaries! It means only that the ovary is above the petals. The flower of Sarracenia, shown in the illustration above, left, is an example of a flower with a superior ovary. The basic flower illustrated in the thumbnail picture at the beginning of the article is one with the ovary below the petals, and that kind is said to have an inferior ovary. The apple blossom is an example of a flower with an inferior ovary.
Next come the complex floral structures, or inflorescences., which is a topic for a whole article by itself. One example to tease you now with, though, is the sunflower. This one looks like a very large flower, but in fact is comprised of hundreds of individual flowers. This type of inflorescence is known as a composite, and the family of plants that includes the sunflower and other similar flowers is known as the Compositae.
Photo credit: Public domain images
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