Plant anatomy comes into play here, as the internal structure of leaves, stems, and roots are unique in their arrangement. Unlike many thorns, which are strong because they are woody, the thorn of Alluaudia ascendens has a strong, corky shield made of dermal tissue that can be pried off to reveal a soft green thorn underneath. Video by Sean Lahmeyer. At The Huntington, we have one of the largest living plant collections in the nation, with diverse plants from around the world growing in assemblages that you would never see in the wild.
And quite a few of them have spines. Equipped with a good razor blade, a microscope, and some dye to stain plant tissue, I was able to make cross sections of many of these spiny structures. What I saw was both beautiful and instructive: Spines, thorns, and prickles are surprisingly different structures, even though they all serve a similar purpose.
Spines, the ones derived from leaves, show many variations worthy of note. Some spines, like those in the Fouquieria family think of an Ocotillo plant from the Mojave Desert , are derived from leaf stalks. Acacia trees in the bean family have spines made of modified leaf stipules.
There are also plants whose entire leaves have been converted into spines, as is the case with cacti. All of these spines are dead at maturity, full of fibers, and no longer capable of photosynthesis. Many plants convert a woody stem into a thorn, and many unrelated plant families share this adaptation, including hawthorn Crataegus in the rose family, Citrus in the rue family, and Natal plum Carissa in the dogbane family. I found one notable exception in Alluaudia , a group of spiny trees endemic to Madagascar.
Their thorns have a hardened outer dermal layer, instead of a stronger internal core, such as wood would provide. A comparison can be drawn to the hard coating, or exoskeleton, of an insect versus the bone, or endoskeleton, of a vertebrate animal—they are both adaptations for structural strength.
Prickles are notable for their complete absence of vascular tissue, the microscopic vessels that conduct sugar and water throughout a plant. Since prickles are sharp projections produced by the skin of a plant, they tend to pop off easily, as they do on rose bushes. The prickles on the silk floss tree Ceiba insignis in the Desert Garden give this tree one of the most handsome trunks in our collection.
Perhaps the most intriguing example of spinescence can be found on the trunk of the tropical palm Cryosophila albida in The Rose Hills Foundation Conservatory for Botanical Science. The palm family is known for having stems and leaves with spiny structures, but there are few examples of palms that produce their shoot spines with root tissue. Indeed, a closer look under the microscope confirmed that the spiny structures on the stem of Cryosophila albida have the internal anatomy of a root, not a stem.
But for a plant, prickliness pays. It is a protective adaptation that allows the plant to survive while facing multiple challenges, the main one being herbivores hoping for a nice snack. In my garden, carnivores of the canine variety are the bigger problem; their rampages through the flower beds in pursuit of squirrels have felled less-protected plants.
But even they now know not to tear through the rose garden. Because it still boggles my mind that spines are …. Didierea madagascariensis Pachypodium lamerei. Aside from being a source of protection, spines serve an important function for xeric plants xerophytes: plants that have adapted to survive in environments with little water; cacti, aloes, agaves and other succulents are xeric plants.
So desert plants had to adapt, or die. Thorns are obtained from shoots. Spines are obtained from leaves and prickles are derived from the epidermis. They all are related to anti-herbivore defense mechanisms of plants. Prickles are extensions of the plants cortex and epidermis the outerlayer of the stem. Functions Protection Also serves as a climbing organ of the plant Protection Prevent excessive transpiration Protection Function like grappling hooks for stems to climb over neighboring objects Example Bougainvillea Many cacti Roses Location Thorns can be located along the branches and twigs of a tree or they can be found along the main trunk It usually forms just below a bud or branch or on leaf Prickles can occur anywhere on the twig or leaf Vascular Bundles Have vascular bundles inside Have vascular bundles inside Are absent.
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Click on the link to send us an email:. The LuEsther T. Do roses have thorns, spines or prickles? Answer In everyday language, people tend to call any sharp appendages on a stem thorns. Topics Roses Plant Morphology. FAQ Actions.
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