Spine
/spaɪn/
Definition
Spine refers to a sharp, stiff, pointed plant structure, usually formed from a modified leaf, leaf part, or stipule. It differs from a thorn, which develops from a stem, and from a prickle, which is an outgrowth of the surface tissue. Spines occur on plants such as cacti and can help reduce water loss, shade the plant surface, and discourage animals from feeding.
Function in Plants
- Defense against herbivores: A spine helps deter browsing animals by making stems, leaves, or fruits harder and more painful to bite, which can reduce tissue loss in dry habitats where replacement growth is costly.
- Reduced water loss: In cacti, a spine replaces much of the protective role of leaves while avoiding the larger surface area that would increase water loss, supporting survival in arid climates.
- Shade and temperature buffering: Dense coverings can cast light shade on the plant surface and slightly reduce overheating, especially on exposed stems that carry out photosynthesis.
- Useful identification feature: The size, number, arrangement, and origin of a spine are important characters in plant identification and can help separate similar succulent groups and species.
Related Terms
Thorn
Thorn refers to a sharp, rigid, pointed plant structure formed from a modified stem or branch. Unlike prickles, which…
Prickle
Prickle refers to a small, sharp outgrowth on a plant’s surface, usually from the epidermis or outer tissues of a stem…
Areole
Areole refers to a small, specialized pad found on cacti, from which spines, hairs, branches, leaves, and flowers can…
Trichome
Trichome refers to a small hair-like or scale-like outgrowth from a plant’s epidermis, the outer cell layer. It may be…
Leaf
Leaf refers to a plant organ, usually flat and green, that grows from the stem or a branch and is specialized for…
Stem
Stem refers to the main aboveground plant structure that supports leaves, buds, flowers, and fruits, and connects them…
Succulent
Succulent describes a plant or plant part with thick, fleshy tissues specialized for storing water. This characteristic…
Spicule
Spicule is a small, slender, pointed or needle-like structure found in certain plants or plant-associated biological…