First, let's look at the spines of cactus for what they really are - the main part of cactus often functions as a modifed stem and its spines are the leaves.
The most obvious function of cactus spines are to protect the cacti from animals and people. There are however, a few animals who aren't deterred by the painful spines of cacti such as javelina, tortoises and pack rats.Another main function of cactus spines is that they help to shade the surface of the cacti.Of course, it may seem that the amount of shade that a single spine offers is infestismal, but when you multiply them by the thousands, the amount of sun protection that they provide is substantial,the shade provided by the spines helps to lower the temperature of the surface of cacti, which limits the amount of water lost through the cactus to the atmosphere.
The cactus life‐form is cited as an example of a tight relationship between organism form and function: a succulent, long‐lived, photosynthetic stem allows cacti to survive long periods of drought while maintaining a positive tissue water status.
Another function that the spines serve is that they help certain species of cacti such as cholla to root and spread.The spines of cholla are specially designed to detach and attach themselves to animals or people who happen to walk by too closely. There are tiny barbs at the tips which grab on to anything that gets too close. It almost appears as if they 'jump' off of the main cactus as they latch on the unlucky recipient.The segments of cholla are then carried to another location where they eventually fall to the ground and then will root and grow into a new cacti under ideal conditions.
Why do cactus plants have thorns?
The most obvious function of cactus spines are to protect the cacti from animals and people. There are however, a few animals who aren't deterred by the painful spines of cacti such as javelina, tortoises and pack rats.Another main function of cactus spines is that they help to shade the surface of the cacti.Of course, it may seem that the amount of shade that a single spine offers is infestismal, but when you multiply them by the thousands, the amount of sun protection that they provide is substantial,the shade provided by the spines helps to lower the temperature of the surface of cacti, which limits the amount of water lost through the cactus to the atmosphere.
The cactus life‐form is cited as an example of a tight relationship between organism form and function: a succulent, long‐lived, photosynthetic stem allows cacti to survive long periods of drought while maintaining a positive tissue water status.
Another function that the spines serve is that they help certain species of cacti such as cholla to root and spread.The spines of cholla are specially designed to detach and attach themselves to animals or people who happen to walk by too closely. There are tiny barbs at the tips which grab on to anything that gets too close. It almost appears as if they 'jump' off of the main cactus as they latch on the unlucky recipient.The segments of cholla are then carried to another location where they eventually fall to the ground and then will root and grow into a new cacti under ideal conditions.