The 10 types of plant stems, and their characteristics

From a botanical point of view, the stem is the analogue of the vertebrate body in plants. This generally aerial plant part supports the leaves, flowers and fruits. Therefore, without it, key events in the life of the plant, such as photosynthesis, pollination or seed dispersal, would not be possible.

Beyond the functional importance of the stem, this structure also allows us to identify different types of vegetables, both in nature and in an agricultural setting. The human being tends to compartmentalize each observable character in living beings, and thanks to this, they can devise and manufacture dichotomous keys, which allow the quick and easy identification of the orders, genera and species that we surround.

So, we encourage you to immerse yourself with us in the world of the types of stems in vegetables and their characteristics. Of course, the complexity that this apparently simple structure contains will leave you amazed.

• Related article: "The 12 most important types of fruits, and their characteristics"

The types of plant stems: a summary of their characteristics

Before starting with the types of stems themselves, we find it necessary to throw a series of data such as preface that, at least, contextualizes the situation of the plants a bit from a point of view morphologic.

Virtually all plant organs are made up of three tissue systems: protective, fundamental, and vascular.. The protection system is formed by the epidermis and the peridermis, both located in the superficial part of the tissues. On the other hand, the fundamental system, formed by the parenchyma and supporting tissues, acts as the "beams" that maintain the shape of the plant itself in three-dimensional space. Finally we have the vascular system: formed by the xylem and the phloem, these tubes serve as transport routes for water and nutrients.

On the other hand, and looking strictly at the stem, we can say that this organ (generally aerial) has various functions. We define them in a few lines below:

• Support the branches, leaves, flowers and fruits.
• Lead the raw sap and the elaborated sap to the different organs of the plant.
• Sometimes carry out photosynthesis.
• Act as a reserve place for processed substances or simply water.
• Act as an organ of reproduction or multiplication.

The stem is made up of nodes and internodes.. The node is the place where at least one leaf develops and there is at least one axillary bud. On the other hand, the internodes are, as their own name indicates, the spaces between two nodes. In addition to all this, at the apical end (in the final part) the stem presents an apical bud, the which is the "original" place of stem emergence and can be classified according to various characteristics.

Once we have made clear the basic notions regarding plant physiology and the stem itself, it is time to dive into the types of stems according to various differential characteristics. let's get started

1. Soil or earth?

Of course, one of the first parameters to classify in the types of stems is if they are aerial or if they are located underground. Epigeal stems are those that grow, as their name suggests, outside the ground.. Depending on their growth pattern, these can be straight or ascending (if they grow vertically) or creeping, if they grow horizontally.

Hypogeous stems are, on the other hand, those that grow underground. It may seem counterintuitive, but indeed, not all vegetative bodies are exposed to the air environment. This group presents some more peculiarities, because according to its morphology, different subtypes can be differentiated. We present some of them:

• Rhizomes: underground stems of variable length and thickness, but all grow horizontally. They have protective scales and adventitious roots.
• Tubers: portions of the stem underground that accumulate a large amount of reserves for the plant.
• Bulbs: very short, erect stems, with roots at the bottom and an apical bud at the top. An example of this is the onion.
• Corms: flattened reserve stems with very short nodes and internodes.

Finally, it should be noted that the hypogeous stems have cataphylls, that is, each of the modified leaves that protect the buds of the plant that are at rest underground. They function as a kind of "scales" that act as armor.

• You may be interested in: "The 4 differences between the animal cell and the plant cell"

2. Consistency

Of course, the stem of a grass is not the same as the trunk of a tree. Despite being the largest aerial portion of the plant in both cases, it is clear that the consistency of the tissues that make up the stem is a clear differential factor.

1. herbaceous stems

In the first place we find the herbaceous stems, that is, those that make up plants that never form permanent woody organs. Secondary or adult tissues are not formed, which is why these stems have a fragile and soft constitution.

Depending on their particularities, these herbaceous stems can be of the scape, cane, calamus, voluble or climbing type. We leave the particularities of each one of them for another opportunity, since we still have a lot of cloth to cut.

2. woody stems

In second instance we have the woody stems, those rigid and hard with a gray or brownish coloration, since they do not have chlorophyll in their chemical constitution. In these cases, secondary tissues do develop, that is, those that provide rigidity, thickness and strength to the root and other structures, growing concentrically around them. Here we have the bushy stems, the arboreal stems and the stipe (such as palm trees).

3. succulent stems

Last (but not least) we have succulent stems, those that they store a large amount of water or nutrients inside as a method of plant survival in inclement environments. Clear examples of this type of stems can be those observed in cacti or aloe vera.

3. Do they photosynthesize or not?

Of course, the ability to carry out photosynthesis is also a clear differentiating element when it comes to distinguishing the different leafy structures. Photosynthetic stems are those that have evolved to perform such an important function due to an adaptive force., which has promoted the disappearance of the leaves in the plant or their change to rudimentary structures.

These stems can be platyclades or cladodes.. The first ones can have the shape of a leaf, since they are green (due to the presence of chlorophyll), flattened and can extend from other more obvious ramifications. An example of this may be the phyllodes of acacias.

On the other hand, cladodes are flattened stems (branches) shaped and colored like a leaf. In these cases, the real leaves are too small or rudimentary to be able to fulfill their task, so with these forms of green "spines" the stems carry out photosynthesis.

As is obvious, the rest of the stems fall within the characteristic of "non-photosynthetic". As they do not have chlorophyll and the bark of the trunks is made up of dead cells, it is physically impossible for these woody stems to perform a function of light absorption.

4. Variety is the key

Finally, we cannot leave ourselves in the dark that, however complex it may be, stems can also be classified according to the structural modifications that present to fit a role. According to this parameter we can observe caulinary tendrils (generally in the form of a spring or spiral, which are used by climbing plants to adhere), thorns caulinares (reduced and pointed branches that act as a defense against predators) or stolons, stems whose apical bud has the capacity to form roots and give rise to a new plant.

Summary

It is hard to believe that, beyond our sight, there is a wide range of characteristics that give stem types names and surnames. These classification criteria allow us to discover the different adaptations that plants have undergone to their environment. environment, and consequently, how they present modifications to maximize their survival in the environment in which they have been touched live.

From the growth in the soil or soil to the photosynthetic capacity, going through the consistency of its tissues and unique morphological structures, the world of stems presents a variety for all tastes and needs.

Bibliographic references:

• Bonzani, N. E., Philippa, E. M., & Barboza, G. AND. (2003). Comparative anatomical study of the stem in some species of Verbenaceae. Annals of the Institute of Biology. Botanical Series, 74(1), 31-45.
• The plant stem: morphology and adaptations. National University of La Plata, Faculty of Agricultural and Forestry Sciences, Plant Morphology Course. Collected on October 25 in https://mvegetal.weebly.com/uploads/8/6/3/4/863437/8_morfologia_tallo_y_adaptaciones.pdf
• Plant organs, Atlas of animal and plant histology. Collected on October 25 in https://mmegias.webs.uvigo.es/descargas/o-v-tallo.pdf
• Stem types, biology the 2000 guide. Collected on October 25 in https://biologia.laguia2000.com/botanica/tipos-de-tallos