Danielle teaches high school science and has an master's degree in science education.
We've been through the basic structures of the shoot system, and now we'll explore a few structures that are involved in the growth of the stem, as well as the types of growth found in plant stems.
As a quick review, the shoot system is the above-ground structure of plants including the leaves, buds, stems, flowers and fruits of plants. We'll focus on the growth of the stem for now, but later on we'll look at other plant structures.
On the stem are several indicators of growth, including nodes and buds. Nodes are where leaves are located. The spaces between nodes are known as internodes. You can remember that internodes are between the nodes by relating the term to similar words. For example, the intermission occurs between different acts of a play and an interchange is between two or more highways.
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Buds also indicate the growth of a plant. There are three main types of buds that we will look at: terminal, lateral and accessory. Terminal buds are located at the tip of the stem. After a terminal bud has developed, it will leave a terminal bud scar. On some plants, the space between a terminal bud and the previous bud scar indicate the amount of growth over the past year. When a bud is not found at the tip of the stem, it is called a lateral bud. These buds are therefore found on the side of a stem. While we just introduced two types of buds, it is important to note that buds do not always form individually and may be accompanied by accessory buds. These are often found in pairs and are located beside terminal or lateral buds.
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The main location of all growth in the stem is found at the meristems, which are the tissues of the stem capable of cell division. There are two types of meristem in the plant stem: apical meristem, which is found at the tip of the stem, and lateral meristem (secondary meristem), which is found surrounding the stem.
The growth at the apical meristem that we will now look at is considered primary growth. This type of growth increases the length of the stem, making the plant taller. It happens in both monocot and dicot plants.
The cell division that occurs at the meristem is what creates new cells and therefore new plant tissue. There are three different types of tissue that the meristem can make: protoderm, ground meristem and procambium. All three types of tissue are then able to make the tissue in a mature stem. The protoderm will eventually make the epidermis of the stem. This is the outer protective covering of the stem. A good way to remember what the protoderm becomes and what the epidermis does is to think of the root word 'dermis,' which means skin. If you have trouble with your skin, you will go to see a dermatologist.
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The ground meristem will make the different types of ground tissue. Previously, we went over the three main types of ground tissue: parenchyma, which is the most common form of tissue and stores water and food, collenchyma, which helps support young stems and roots, and sclerenchyma, which is hard tissue that provides support and protection for the stem. All three types of ground tissue come from the ground meristem.
The third tissue made by the apical meristem is procambium, which will make the vascular tissue. Remember that vascular tissue includes both xylem, which carries water, and phloem, which carries food.
Plants need to grow for several reasons, including the need to access sunlight to make food. The nodes and buds found on the stem are indicators of plant stem growth. Remember that all forms of growth must occur at the meristem, as this is the location of cell division. In order to get taller, plants go through primary growth, which occurs at the apical meristem. This area of cell division creates three types of tissue - protoderm, ground meristem and procambium - which will later become mature structures in the plant stem.
By the conclusion of this video, you'll be able to:
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