Thorns, spines, and prickles are three types of structures that appear in plants which have a similar appearance, but which are derived from different plant organs. All three are hard structures with sharp, pointy ends, which are generally used by plants to protect themselves from herbivores.

Thorns are modified branches or stems, spines are modified leaves, and prickles are needle-like extensions of the cortex and epidermis.^[1] These three types of structures are often confused, although they are technically distinct.^[2][3] Many plants commonly thought of as having thorns actually have spines or prickles. Roses, for instance, have prickles.

Some plants have thorns, spines, or prickles which can pierce animal's skin. Examples of these among the thorns are the lemon, pomegranate and wood apple. Thorns likely first evolved as a defense mechanism in plants growing in sandy environments which provided inadequate resources for fast regeneration.^[4][5]

[edit] Thorns, spines, and prickles in human culture

Primitive humans are known to have used thorns as tools. Human history records a variety of cultural references to sharp-pointed plant defensive mechanisms. The Book of Genesis recounts the creation of thorns as one of the punishments for the sin of Adam and Eve, stating "Thorns also and thistles shall [the ground] bring forth to thee; and thou shalt eat the herb of the field." Genesis, 3:18. One of the most enduring cultural images is the Crown of Thorns described in the Bible as having been placed on the head of Jesus before his crucifixion. It is mentioned in the Gospels of Matthew (27:29), Mark (15:17), and John (19:2, 5) and is often alluded to by the early Christian Fathers, such as Clement of Alexandria, Origen, and others. For example, John the Evangelist states that "the soldiers plaited a crown of thorns, and put it on his head". (KJV, ch. 19). The Biblical account does not specify what kind of thorns were involved, and leaves no clues from which to determine whether these were biologically classifiable as thorns, spines, or prickles.

An early popular myth involving a thorn is that of Androcles, a fugitive slave in ancient Greece who was said to have befriended a lion by pulling a thorn from the lion's paw.

Plants bearing thorns, spines, or prickles are often used as a defense against burglary, being strategically planted below windows or around the entire perimeter of a property.

[edit] References

• Esau, K. 1965. Plant Anatomy, 2nd Edition. John Wiley & Sons. 767 pp.
• Llamas, K. A. 2003. Tropical Flowering Plants. Timber Press, Portland. 423 pp.

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