The 10 types of plant stems and their characteristics

This is a summary of the different types of stems that exist in the botanical world.

From a botanical point of view, the stem is the analog of the vertebrate body in plants. This generally aerial plant part supports the leaves, flowers and fruits. Therefore, without it, key events in plant life, 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 plants, both in nature and in an agricultural environment. Humans tend to compartmentalize every observable character in living beings, and thanks to this, dichotomous keys can be devised and fabricated, which allow the quick and easy identification of the orders, genera and species that surround us.

So, we encourage you to dive with us into the world of the types of stems in types of stems in vegetables and their characteristics.. Of course, the complexity that encloses this seemingly simple structure will leave you amazed.

The types of stems of plants: a summary of their characteristics.

Before starting with the types of stems themselves, we see it necessary to throw a series of data as a preface that, at the very least, contextualize us a little the situation of plants from a morphological point of view.

Practically all plant organs are made up of three tissue systems: the protective, the fundamental and the vascular.. The protective 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 phloem, these tubes act 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 several functions. We define them in a few lines below:

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

The stem is formed by 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 its name indicates, the spaces between two nodes. In addition to all this, at the apical end (in the final part) the stem has an apical bud, which is the "primordial" place of the emergence of the stem and can be classified according to various characteristics.

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

Soil or soil?

Of course, one of the first parameters to classify stem types is whether they are aerial or located below the ground. Epigeal stems are those that grow, as their name indicates, outside the soil.. Depending on their growth pattern, they can be upright or ascending (if they grow vertically) or creeping, if they grow horizontally.

Hypogeous stems, on the other hand, are those that grow underground.. It may seem counter-intuitive, but indeed, not all vegetative bodies are exposed to the aerial environment. This group presents some more peculiarities, because according to their morphology, different subtypes can be differentiated. Here are some of them:

• Rhizomes: subway stems of variable length and thickness, but all grow horizontally. They have protective scales and adventitious roots.
• Tubers: underground portions of the stem 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 internodes and nodes.

Finally, it should be noted that hypogeous stems have cataphylls, i.e., each of the modified leaves that protect the buds that are at rest underground.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.

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 differentiating factor.

1. Herbaceous stems

In the first place we find the herbaceous stems, i.e. those that constitute the plants that never grow, those that constitute the plants that never form permanent woody organs.. No secondary or adult tissues are 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 will leave the particularities of each of them for another opportunity, as we still have a lot of work to do.

2. Woody stems

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

3. Succulent stems

Last (but not least) we have the succulent stems, which are those that 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 observed in cacti or aloe vera.

3. Do they photosynthesize or not?

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

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

On the other hand, cladodes are flattened stems (branches) with the shape and coloration of a leaf. In these cases, the actual leaves are too small or rudimentary to be able to fulfill their task, so with these green "thorn" forms the stems perform photosynthesis.

As is obvious, the rest of the stems fall into the category of "non-photosynthetic". Since they do not possess chlorophyll and the bark of the stems is composed of dead cells, it is physically impossible for these woody stems to perform a light-absorbing function.

4. Variety is the key

Finally, we must not forget that, however complex it may be, stems can also be classified according to the structural modifications they undergo. according to the structural modifications they undergo to adapt to a function. Depending on this parameter we can observe cauline tendrils (generally spring or spiral shaped, which are used for climbing plants to adhere to), cauline spines (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 names and surnames to the types of stems. These classificatory criteria allow us to discover the different adaptations that plants have undergone to their environment, and consequently, how they present modifications to maximize their survival in the environment in which they have had to live.

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

Bibliographical references:

• Bonzani, N. E., Filippa, E. M., & Barboza, G. E. (2003). Comparative anatomical study of stems in some species of Verbenaceae. Annals of the Institute of Biology. Botany Series, 74(1), 31-45.
• The stem of plants: morphology and adaptations. Universidad nacional de la plata facultad de ciencias agrarias y forestales curso de morfología vegetal. Retrieved October 25 from 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 at https://mmegias.webs.uvigo.es/descargas/o-v-tallo.pdf.
• Types of stems, biology the guide 2000. Picked up on October 25 at https://biologia.laguia2000.com/botanica/tipos-de-tallos.