THORNS

Thorns, spines, and prickles, as well as other spinose structures (also known as spinose teeth or spinose apical processes) in plant morphology, are hard, rigid extensions or adaptions of leaves, roots, stems, or buds with sharp, stiff ends that all serve the same purpose: physically deterring animals from having eaten the plant material.

DESCRIPTION:

Thorns are generated from shoots (which may or may not be branched, have leaves, or develop from a bud), spines are derived from leaves (either the complete leaf or a portion of the leaf with vascular bundles inside, such as the petiole or a stipule), & prickles are derived from epidermal tissue (so that they can be found somewhere on plaza).

Leaf margins can also have teeth, which are known as spinose teeth on a spinose outer edge (some writers consider them a type of spine).

If there is an apical process (usually an extension of the midvein) on the leaf apex that is particularly sharp, stiff, and spine-like, it is known as spinose or a pungent apical procedure (again, some authors call them a type of spine).

When the leaf epidermis is covered with very lengthy, stiff trichomes (more accurately called bristles in this case; for some writers, a type of prickle), it is called a hispid vestiture; when the trichomes are stinging trichomes, it is called a urent vestiture.

Spines or spinose structures derived from roots can also be discovered.

FUNCTION:

The basic task of thorns, spines, & prickles is to mechanically prevent herbivory. As a result, they’re categorized as physical or mechanical defenses rather than chemical defenses.

Spines and glochids have more purposes than just defending against physical attacks by herbivores as well as other animals. Spines have been demonstrated to shade or insulate the plants which they grow, shielding them from harsh temperatures in some situations.

 In the summer, saguaro cactus spines shade the apical meristem, and in the winter, glochids insulate the apical meristem in members of the Opuntioideae.

Spines appear to have little influence on specialized pollinators, that many plants rely for reproduction, according to Agrawal et al. (2000).

TECHNICAL DISTINCTIONS:

Thorns and spines are formed from shoots and leaves, respectively, and contain vascular bundles inside, whereas prickles (such as rose prickles) do not have vascular bundles within it, allowing them to be removed more readily and cleanly than thorns and spines.

THORNS:

Thorns are branches or stems that have been changed. They might be unbranched or branched.

SPINES:

Spines are leaves, stipules, or sections of leaves that have been changed, such as leaf vein extensions. Some authors prefer not to separate spines from thorns because, like thorns, they often contain vascular tissue, whereas prickles do not.

Petiolar spines (as in Fouquieria), leaflet spines (as in Phoenix), and stipular spines (as in Euphorbia) are all instances of spines that originate from a region of the leaf that contains the petiole, midrib, or secondary vein. 

Plants in the cacti family are notable for their extensive spine covering. Glochids (or glochidia, singular glochidium) are a type of spine found in some cacti that is smaller, deciduous, and has multiple retrose barbs running the length of it.

PRICKLES:

Prickles resemble hairs; however, they can be fairly coarse (for example, rose prickles). They are the cortex and epidermis’ extensions. Many plants that are usually mistaken for having thorn or spines really have prickles. Prickly roses, for example, have prickles.

OTHER STRUCTURES:

Spinose teeth, spinose apical process, and trichomes are other structures that are comparable. Trichomes differ from thorns, spines, as well as prickles in that they are much relatively small (often microscopic) epidermal tissue outgrowths that are less rigid and much more hair-like in appearance; they typically consist of only a few cells of the epidermis’ outermost layer, whereas prickles may include cortex tissue. 

Thorns, spines, and prickles are mainly only useful against larger herbivores like birds and animals; trichomes are often excellent protection against small insect herbivores.

Spines formed from roots, such as those on the stem of “Root Spine Palms,” are also present. Cryosophila guagara’s trunk roots grow to a size of 6–12 cm before stopping and transforming into a spine.

The anatomy of crown roots on this species (roots among the bases of the living fronds) also alters during their life. They initially grow upwards and then turn down and finally they, become spinous. 

The lateral roots of these two types of roots, as well as those of this species’ stilt roots, grow spiny. Some authors believe that some of these short spiny laterals have a ventilating function so they are ‘pneumorhizae’. On the roots of Iriartea exorrhiza, there are short spiky laterals that may have a ventilation role. 

On the palm Euterpe oleracea, there are additional spines that act as pneumorhizae. There are spine roots and root spines in Cryosophila nana (previously Acanthorhiza aculeata); some authors prefer “root spines” if the length of the root is less than 10x the thickness, and “spine roots” if the length is plenty 10x the thickness. 

Adventitious spiky roots have also been observed on the trunks of dicotyledonous trees in tropical Africa (e.g., Euphorbiaceae, as in Macaranga barteri, Bridelia micrantha, and Bridelia pubescens; Ixonanthaceae, Sterculiaceae), and may also protect perennating organs like tubers as well as corms (e.g., Dioscorea prehensilis -Dioscoreaceae- & Moraea spp. -Iridaceae- respectively). 

The tuberous base of epiphytic ant-plant Myrmecodia tuberosa (Rubiaceae) is covered in short root spines, which provide protection to ants that walk over the plant’s surface and live in chambers within the tuber (Jackson 1986 and references therein). In many ways, the production of spines resembles the formation of thorns from lateral branches. 

EVOLUTION:

It’s been suggested that thorny structures arose as a defense strategy in plants that grow in sandy conditions with insufficient resources for speedy harm recovery.

HUMAN APPLICATIONS:

Plants with thorns, spine, or prickles are frequently employed as a deterrent to burglars, and are carefully planted beneath windows and around the perimeter of a house. They’ve also been used to keep marauding animals away from farms and cattle. 

Hawthorn hedges in Europe, agaves in the Americas and other areas where they have been introduced, Osage orange in the United States’ prairie states, and Sansevieria in Africa are just a few examples.

CONCLUSION:

The sharp tips on some trees and plants, such as a rose bush, are known as thorns. Roses always have thorns, but they can be prevented with care. 

Thorns can be found in the leaf axils or at the stem’s apex. These are all the modified stems which serve as either a defense or a climbing aid. Duranta, Bougainvillea, and Climbing Rose, for example.

Thorns, spines, & prickles, as well as other spinose structures, are hard, stiff extensions or alterations of leaves, roots, stems, or buds with sharp, stiff ends that serve the same purpose in plant morphology: physically preventing animals from consuming the plant material.