Characteristics and functions of plant spines

Cactus spines are modified leaves

Just mentioning the word "thorns" immediately comes to mind a very peculiar type of plant: the cactus. Living in areas where temperatures can reach and even exceed 50 degrees Celsius, and where the rains are seasonal, the best way to save water they have found is not to produce leaves; or at least, not common leaves.

The truth is that there are different types of thorns, and each of them have their functions. So If you want to know everything about this incredible protection system (among other things) that some plants have, do not take your eyes off the monitor .

What are thorns in botany?

There are plants that have thorns on the stems

Thorns (in botany) They are formations with a sharp tip that can be branched and that, as they have vascular tissue, their content in support tissue is very high. This also makes them rigid, unlike other similar structures such as stingers, which do not have vascular tissue.

Why do some plants have them? Well, let's imagine for a moment that we are a plant and we live in an arid region, be it desert, steppe, dry forest or a thorn forest. In those places the insolation is not only high, but apart from that we would have to overcome another problem, if possible, greater: the scarcity of water. It can rain a lot for several days or weeks a year, but drought complicates our lives most months.

In our favor we have a very strong survival instinct, typical of all living beings. But the production and maintenance of leaves is a rather large expense of water, an expense that we cannot afford. What do we do?

Explaining it in a simplified way, over the years (hundreds, thousands or maybe millions of years), and as long as the conditions of the region remain more or less the same, we will stop producing common leaves to gradually transform them into thorns, which do not require as much water and those that, in addition, can serve us for other very important things that we will see below.

What types are there?

There are several types of thorns, depending on their origin:

  • Caulinar thorns: are those that originate from the transformation of the stems, and can also be called reduced branches. For example, him prunus spinosa or the Gleditsia triacanthos they own them.
  • Leaf spines: are those that originated from the transformation of the leaves, like all those plants of the Cactaceae (cactus) family, and those of the Berberis genus.
  • Radical thorns: they are the result of the modification of the root, which occurred through a lignification process. They are very rare.

What is the function of plant spines?

Cacti have thorns to reduce water loss

The spines of the plants fulfill different functions, which are the following:

Reduce perspiration

As we just discussed, these structures require less water both in their production and in their maintenance. But in addition, they lack stomata, which are two occlusive cells that are found in the epidermis (skin) of plants and that delimit a pore between them through which the gases inside the plants and those outside are communicated.

Thus, the loss of the precious liquid is much less.

They protect them from predators

As we know, there are herbivorous animals, and others that like to eat plants from time to time. If to these 'dangers' we add the drought and extreme heat that can be in certain places, it is crucial to protect yourself. And the best way to do it is by producing thorns.

Although they cannot always fulfill their function (for example, when the predator is a voracious snail), they are generally very helpful in keeping you safe.

They serve as a bit of an 'umbrella'

The fact that a plant has its entire body covered by thorns, it's a way to protect yourself from the sun. Of course, this protection will be greater or less depending on the characteristics of these spines: if they are long and very numerous, without a doubt your body will not be as exposed to the star king as if you only have some and / or if you have them very short.

They can collect water

Whether it rains or the only thing there is is dew, every drop of water that is deposited on the thorns is directed to the body of the plants, where they will be absorbed through the pores. With this system then, they can stay hydrated, even if they live in the desert.

How useful are thorns for humans?

Today, plants with thorns have a use merely ... defensivo. They are very interesting to have for example as protection hedges; although there are some that are collected for the beauty of their defensive structures, such as cacti.

On the other hand, it is known that in the past, and still today, indigenous tribes use them as tools, often hunting.

5 plants with thorns for garden

To finish, if you want to have thorny plants in your garden, then we are going to recommend these five:

Asparagus falcatus

View of Asparagus falcatus

Image - Wikimedia / Ewen Cameron

Known as sickle asparagus, the Asparagus falcatus It is a spiny plant with broad leaves that could well be mistaken for a bamboo ... although it is not at all. It is native to southern Africa, and is a climbing and evergreen shrub that reaches a height of 6 to 7 meters. Its flowers are white and perfumed.

It does not resist frost. Suitable for indoor cultivation.


Berberis are thorny shrubs

El berberis is a genus of evergreen or deciduous spiny shrubs depending on the species native to Europe, Asia, Africa, North and South America that reach a height of about 1-4 meters. The flowers are simple or in clusters, yellow or orange, and the fruits are edible berries but difficult to collect due to the amount of thorns that these plants have.

They resist cold and frost down to -12ºC.

Echinocactus grusonii

The Echinocactus grusonii is a prickly cactus

Known as mother in law seat, golden ball, golden barrel or hedgehog cactus, the Echinocactus grusonii it is a species of cactus armed with strong spines endemic to central Mexico. It has a globular and spherical body, which over time can grow to be over 1 meter tall.

It resists weak frosts down to -2ºC.

Phoenix dactylifera

The date palm is a spiny palm

Known as date, common palm, phoenix, tamara or palm / palm tree, the Phoenix dactylifera It is a species of palm native to southwestern Asia. It grows to a height of 30 meters, with a solitary or multicaule trunk (with several stems) of 20 to 50cm in diameter each. The leaves are pinnate and spiny, and its flowers are grouped in inflorescences that sprout from spathes (modified leaves that protect the flowers) of brown color. The fruits are dates, red-chestnut berries when ripe and edible.

Resists cold and frost down to -12ºC. In the Canary Islands it is considered an invasive plant, and their trade, possession and introduction to the environment is prohibited.

prunus spinosa

Blackthorn is a thorny bush

Known as blackthorn, prunus spinosa is a deciduous and thorny shrub native to Central and Southern Europe that reaches a height of 4 to 5 meters. Its crown is very dense and branched, and it blooms in spring producing white flowers. The fruit is the blackthorn, an oval drupe of blue, purple or blackish color appreciated for the elaboration of pacharán.

Resists up to -18ºC.

What did you think of this topic? Did you know that plant spines could have so many functions?

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