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Prickles on a blackberry branch. In plant morphology, thorns, spines, and prickles, and in general spinose structures (sometimes called spinose teeth or spinose apical processes), are hard, rigid extensions or modifications of leaves, roots, stems, or buds with sharp, stiff ends, and generally serve the same function: physically defending plants against herbivory.
Spinous cells are found in the superficial layers of the skin. They are found in the stratum spinosum (prickly layer, spinosum layer), which lies above the stratum basale (basal layer) and below the stratum granulosum (granular layer) of the epidermis. The spinous cells are arranged several layers thick to form a net-like covering. [1]
A new study has found how a rose and other plants like a tomato and eggplant came to get their prickles. The discovery could help engineer new thorn-free variants.
Viburnum lesquereuxii leaf with insect damage; Dakota Sandstone (Cretaceous) of Ellsworth County, Kansas. Scale bar is 10 mm. Knowledge of herbivory in geological time comes from three sources: fossilized plants, which may preserve evidence of defense (such as spines) or herbivory-related damage; the observation of plant debris in fossilised animal feces; and the structure of herbivore mouthparts.
The spines are the relatively large, radiating organs; the glochids are the fine prickles in the centres of the bunches. Glochids ( Opuntia microdasys monstrose ) Glochids or glochidia ( sg. : "glochidium") are hair-like spines or short prickles, generally barbed, found on the areoles of cacti in the sub-family Opuntioideae .
Some plants have physical defenses such as thorns, spines and prickles, but by far the most common type of protection is chemical. [ 1 ] Over millennia, through the process of natural selection , plants have evolved the means to produce a vast and complicated array of chemical compounds to deter herbivores.
The hooks or teeth generally cause irritation, and some species commonly cause gross injury to animals, or expensive damage to clothing or to vehicle tires. [citation needed] Burs serve the plants that bear them in two main ways. Firstly, burs are spinescent and tend to repel some herbivores, much as other spines and prickles do. [3]
For example, the article says that spines are derived from leaves, but none of the four sources I listed at User:Peter coxhead/Work page#Spines vs. thorns restrict the term to leaf-derived structures. Also, the use of spinosus as an epithet is relevant; many plants with such names have what the article calls "thorns", e.g. Prunus spinosa.