Definition Structure and Functions of Thorns and Spines
It is difficult to spot the difference between thorns and spines based only on their appearance since they both look almost identical. To know what is the difference between thorns and spines, we must look at how these two are created from different parts of a plant. While the thorn is a modified stem, the spine is a modified leaf. At Vedantu, we have created a comprehensive summary of spines, thorns, and pickles along with their differences.
Spines
Spines are sharp, pointed structures on a plant and are modified leaves. They protect the plant from predators. An example of spines can be seen in the Opuntia plant where the minute leaves of axillary buds transform into spines. Another example is pineapple where the margin of leaves is modified into spines.
Thorns
Thorns are woody, pointed structures in a plant that protect the plant and help in climbing. They are modified axillary leaves and are different from both spines and prickles. Thorns may be branched or unbranched and are always subtended by a leaf.
What is the Difference between Thorns and Pickles?
Spines are structures that are sharp in nature and are pointed. They are part of the plant and are modified leaves. These provide protection of the plants from predators. An example of spines is observed in the Opuntia plant where the leaves or buds of the axillary transform into spines. Another example of such plants is pineapples which have the margin of their leaves modified into spines. Spines are thus modified leaves or stipules which are parts of the leaves and have extensions of the leaf veins. The spines have vascular tissues. They are also called petiolar spines or leaflet spines and even stipular spines which are examples of spines that develop as a leaf part that has midrib, petiole, and secondary veins. Spines are observed widely in the family of cactus. The cacti have a particular kind of spine that is of different origin and are called glochids. The glochids are small and deciduous with many retrorse barbs along the length of the plant. Thorns on the other hand are woody and pointed structures that protect the plant and also help them in climbing other surfaces. They are axillary leaves that are modified and they differ from prickles and spines. The thorns are either branched or not branched.
The terms prickles and thorns are often mixed and used interchangeably but there is a slight difference between thorns and prickles.
While thorns are formed from internal tissue (endogenous), prickles develop from external tissue ( exogenous).
Prickles develop from the epidermis and cortex of plant stems while thorns are modified branches.
Prickles can also occur on leaves and protrude from the main veins of the leaf unlike thorns
Prickles can also be seen on adventitious roots and some fruits unlike thorns
An example of prickles is the rose plant.
Spines, thorns, and prickles all prevent the animals from eating the plant.
Let’s look at the difference between thorns and spines in detail.
FAQs on Difference Between Thorns and Spines in Plants
1. What is the difference between thorns and spines?
The main difference between thorns and spines is their origin: thorns are modified stems, while spines are modified leaves or parts of leaves.
- Thorns arise from axillary buds and are hard, woody, and deeply connected to the stem.
- Spines develop from leaf structures such as the entire leaf, stipules, or parts of a leaf.
- Both serve mainly for protection against herbivores.
2. What are thorns in plants?
Thorns are sharp, pointed structures that are modified stems in certain plants.
- They develop from axillary buds.
- They contain vascular tissue connected to the main stem.
- Example: Bougainvillea and Citrus plants.
3. What are spines in plants?
Spines are sharp structures formed by the modification of leaves or parts of leaves.
- They may arise from the entire leaf, stipules, or leaf margins.
- They contain vascular tissue but are not derived from buds.
- Example: Cactus spines and Opuntia.
4. How can you identify whether a structure is a thorn or a spine?
You can identify a thorn or spine by examining its point of origin on the plant.
- If it arises from an axillary bud, it is a thorn.
- If it originates from a modified leaf or stipule, it is a spine.
- Thorns are usually woody and branched, while spines are often simpler.
5. What is the function of thorns and spines?
The primary function of both thorns and spines is protection against herbivores.
- They deter animals from feeding on the plant.
- In some desert plants, spines reduce water loss by minimizing leaf surface area.
- They may also provide slight shade to reduce transpiration.
6. Are thorns and spines the same as prickles?
No, thorns and spines are different from prickles in their origin and structure.
- Thorns are modified stems.
- Spines are modified leaves.
- Prickles are outgrowths of the epidermis or cortex and lack vascular tissue.
7. Why do cactus plants have spines instead of leaves?
Cactus plants have spines instead of leaves to reduce water loss in arid environments.
- Spines are modified leaves that minimize surface area.
- They reduce transpiration.
- They also protect against herbivores.
8. Can a plant have both thorns and spines?
Yes, a plant can have both thorns and spines if different organs are modified for protection.
- One structure may arise from a modified stem (thorn).
- Another may arise from a modified leaf (spine).
- This depends on the species and evolutionary adaptations.
9. What are some examples of plants with thorns and spines?
Examples of plants with thorns and spines highlight their different structural origins.
- Plants with thorns: Bougainvillea, Citrus, Pomegranate.
- Plants with spines: Cactus, Opuntia, Berberis (stipular spines).
10. How do thorns and spines help in plant adaptation?
Thorns and spines help in plant adaptation by enhancing defense and reducing water loss.
- They prevent damage from herbivores.
- Spines reduce transpiration in dry climates.
- They may assist in mechanical support or shading.
