What does callose mean?
Callose is a specialized plant polysaccharide — a glucose polymer linked in β-1,3 chains — that plays a vital role in how plants protect their vascular system. It is deposited in the walls and sieve plates of phloem sieve tubes, the conduits that carry sugars through the plant. When a sieve tube is wounded or reaches the end of its life, callose accumulates rapidly around the pores, effectively plugging the channel and preventing the loss of precious sap and the entry of pathogens. This rapid sealing response can occur within seconds to minutes of injury, making callose a key player in plant wound defense. The term belongs firmly to the vocabulary of botany and plant pathology, appearing in research on phloem function, viral infection, and grafting, and it shares an etymological root with words such as callus and callous, all tracing back to a Latin word for hardened skin.
nounA polysaccharide (a β-1,3-linked glucan) found in plants, deposited in the cell walls and sieve plates of phloem tissue, where it can seal off damaged or aging sieve tubes.
- (Botany) A β-1,3-glucan polysaccharide deposited in the walls and sieve plates of plant phloem cells, where it seals off damaged or senescing sieve tubes.
"Within seconds of the leaf being wounded, callose was deposited across the sieve plate, sealing the severed tube."
"The researcher stained the section with aniline blue, which fluoresces brightly wherever callose is present."
"As the sieve tube approached senescence, heavy callose accumulation gradually blocked the pores of the sieve plate."
Rarely pluralized; callose is normally treated as an uncountable substance noun in scientific writing.
"Different plant tissues showed distinct staining patterns for their various calloses."
When a plant is wounded, it can wall off its own plumbing with callose in a matter of seconds — a self-sealing repair no engineer has quite matched.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of callose
The term callose derives from Latin callosus, meaning 'thick-skinned' or 'hardened', itself formed from callus, the word for hardened skin — the same Latin root that gives English callus, callous, and callosity. Botanists adopted it in the 19th century for the substance that thickens and seals plant sieve tubes, drawing an analogy between the hardened patches in plant tissue and calloused skin.
How callose is actually used
Strictly a scientific term, used almost exclusively in botany, plant physiology, and plant pathology literature. It functions as an uncountable substance noun, much like 'cellulose', so it takes no plural in normal academic writing.
Easily confused with callose
Callous means emotionally unfeeling or physically thickened and hardened, whereas callose is a technical botanical term for a specific plant polysaccharide.
A callus is a mass of hardened skin or plant tissue that forms over a wound, while callose is a carbohydrate substance rather than a tissue type.