Plants can’t walk or run. They can’t go off in search of the nearest river when they’re thirsty. They can’t hide when a predator comes or heavy snow falls. So they’ve developed special defenses to protect themselves from animals, from drying up, and from the cold.
In order to defend themselves from animals that want to eat them, the leaves and the stems of some plants are transformed into thorns, prickles, or spines.
Thorns are modified branches or stems.
Roses actually have prickles, not thorns. Prickles are extensions of the plant “skin.” They are also found in thistles.
Spines, such as those of the cactus plant, are actually modified leaves.
Spines, thorns and prickles are stiff and sharp and prevent animals from eating the plant.
Spines not only protect the cactus from animals; they also keep the cactus from losing much water by reducing the flow of air around it and by providing shade. This is important because cacti usually live in very dry environments like deserts.
Another way they keep from drying up is by transforming their stems into water containers.
Did you know that those thick, green, fleshy parts of cacti are actually their stems? Those specialized stems are where they store water, and that’s how they can live without rain for a very long time.
Plants defend themselves from the cold by developing very thin, pointed leaves, like needles.
Because the needles are narrow, they keep snow from building up and breaking the branches of the tree.
The needles are also covered with a thick, waxy film, which protects them from the cold and prevents moisture loss.
Plants that are not able to develop leaves like needles have to lose their leaves and “hibernate” during winter.