The stem is a part of the plant that mainly has the function of conducting substances and supporting . It is an organ that together with the leaves makes up the stem system.
Stems and leaves are closely associated in their development. The leaves sprout in the peripheral region of the stem and are arranged according to the organization of your vascular system.
The plant can grow for its entire life, thanks to meristems. Primary growth occurs in the longitudinal direction, lengthening the plant, and secondary growth promotes an increase in width.
Stem Types
- Trunk is the vertical stem. Larger plants are found in trees.
- Rhizomes are underground and grow horizontally. They are long and delicate.
- Stolons are elongated and grow horizontally along the surface of the soil.
- Tubers have a storage function. The English potato is a well-known example of a tuber. On its surface there are small depressions from which protuberances arise, are the buds.
- Bulbs are small, cone-shaped stems. They have a large yolk and many modified leaves. Examples are the onion and the lily.
- Tendrils are a very common modification of the stem (in some cases of the leaf). They assist in support by wrapping themselves around the main support structure. Vines are an example.
Occupation
The stem has two main functions: support and conduction of substances, but it can also serve as a nutritional reserve.
- Conduction: the substances produced in the leaves (elaborated sap) are transported by the stem, through the phloem. These compounds are taken to all parts of the plant, where they will be consumed. The transportation of raw sap (water and mineral salts) is done by the xylem, going from the roots to the leaves.
- Support : The stem supports the leaves, so that they are able to receive more light to perform photosynthesis.
- Storage : some underground stems are adapted for storage, as is the case with English potatoes.
Structure and Development
The stem structure has apical growth , in other words, the stem grows from the apex, which is a primary meristem .
The meristem is a tissue that produces undifferentiated cells that are used for the growth of the plant, it is also called yolk.
The plant embryo (before germinating) consists of a stem, one or more rudimentary leaves and an apical meristem. With its development, new leaves are formed from the apical bud and the stem grows.
As the stem lengthens, knots and internodes differ. The nodes are the regions of the stem from which the leaves come out. The spaces between one node and another is called internode .
At this point, lateral buds appear in the leaf axils. They are protuberances that will originate the lateral branches of the stem.