# Root cap

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Root_cap
> Markdown URL: https://mediated.wiki/source/Root_cap.md
> Source: https://en.wikipedia.org/wiki/Root_cap
> Source revision: 1297246319
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Tissue at the tip of a plant root

Root tip magnified 100×. 1. [Meristem](/source/Meristem) 2. [Columellae](/source/Columella_(botany)) ([statocytes](/source/Statocyte) with statolithes) 3. Lateral part of the tip 4. Dead cells 5. Elongation zone

The **root cap** (also called the **calyptra**) is a small but multitasking organ that covers the very tip of every growing plant [root](/source/Root). It shields the delicate [apical meristem](/source/Apical_meristem) from mechanical damage, lubricates the root's passage through soil, and houses specialised [gravity-sensing](/source/Gravitropism) cells that guide the root's overall direction of growth.

## Structure and function

Root caps contain [statocytes](/source/Statocyte) ([gravity-sensing](/source/Gravitropism) cells) whose dense statoliths settle in response to gravity; if the cap is carefully removed a root loses its orientation and grows at random. The cap also secretes a layer of [mucilage](/source/Mucilage) that reduces friction and may foster signalling with the surrounding soil [microbiota](/source/Microbiota).[1] Because of its sensor cells, the organ underpins [gravitropism](/source/Gravitropism) (sometimes called geoperception), helping the root grow downwards with gravity or reorient upwards against it.[2][3]

## Development and turnover

The root cap is renewed continuously. Stem-cell files on its inner face divide to generate successive layers of [columella](/source/Columella_(botany)) and lateral root-cap cells; as the root advances, the oldest outer layers are sloughed off so the organ maintains a steady size. In [cereals](/source/Cereal) and many [legumes](/source/Legume) these discarded layers separate as long-lived "border cells", whereas in *[Arabidopsis thaliana](/source/Arabidopsis_thaliana)* most surface cells undergo rapid, developmentally-[programmed cell death](/source/Programmed_cell_death) before shedding.[4]

## Sensory roles and variation

Beyond sensing gravity, the cap acts as a broader signalling hub. Asymmetric redistribution of the plant hormone [auxin](/source/Auxin) in its statolith-bearing cells initiates curvature that restores the root to the gravity vector; related pathways also mediate water-seeking ([hydrotropism](/source/Hydrotropism)) and help position future [lateral roots](/source/Lateral_root), shaping overall root-system architecture.[4]

A true root cap is absent in some [parasitic plants](/source/Parasitic_plant)[5] and several [aquatic plants](/source/Aquatic_plant), which instead form a thin, sac-like *root pocket* that performs a reduced protective role.[6]

## References

1. **[^](#cite_ref-Raven_&_Edwards_2001_1-0)** Raven, J.A.; Edwards, D. (2001). ["Roots: evolutionary origins and biogeochemical significance"](https://doi.org/10.1093%2Fjexbot%2F52.suppl_1.381). *Journal of Experimental Botany*. **52**: 381–401. [doi](/source/Doi_(identifier)):[10.1093/jexbot/52.suppl_1.381](https://doi.org/10.1093%2Fjexbot%2F52.suppl_1.381). [PMID](/source/PMID_(identifier)) [11326045](https://pubmed.ncbi.nlm.nih.gov/11326045).

1. **[^](#cite_ref-Burgess_1985_2-0)** Burgess, Jeremy (1985). [*Introduction to Plant Cell Development*](https://books.google.com/books?id=r808AAAAIAAJ&dq=root+cap&pg=PA108). CUP Archive. [ISBN](/source/ISBN_(identifier)) [9780521316118](https://en.wikipedia.org/wiki/Special:BookSources/9780521316118).

1. **[^](#cite_ref-Kuya_&_Sato_2011_3-0)** Kuya, Noriyuki; Sato, Seiichi (2011). "The relationship between profiles of plagiogravitropism and morphometry of columella cells during the development of lateral roots of *Vigna angularis*". *Advances in Space Research*. **47** (3): 553–562. [doi](/source/Doi_(identifier)):[10.1016/j.asr.2010.09.009](https://doi.org/10.1016%2Fj.asr.2010.09.009).

1. ^ [***a***](#cite_ref-Kumpf_&_Nowack_2015_4-0) [***b***](#cite_ref-Kumpf_&_Nowack_2015_4-1) Kumpf, Robert P.; Nowack, Moritz K. (2015). "The root cap: a short story of life and death". *Journal of Experimental Botany*. **66** (19): 5651–5662. [doi](/source/Doi_(identifier)):[10.1093/jxb/erv295](https://doi.org/10.1093%2Fjxb%2Ferv295). [PMID](/source/PMID_(identifier)) [26068468](https://pubmed.ncbi.nlm.nih.gov/26068468).

1. **[^](#cite_ref-Jeffrey_2007_5-0)** Jeffrey, Edward Charles (2007). *The Anatomy of Woody Plants*. Pomeroy, Ohio: Carpenter Press. p. 138. [ISBN](/source/ISBN_(identifier)) [978-1-4067-1634-4](https://en.wikipedia.org/wiki/Special:BookSources/978-1-4067-1634-4).

1. **[^](#cite_ref-Gupta_2007_6-0)** Gupta, P.K. (2007). *Genetics: Classical to Modern*. Rastogi Publications. pp. 2–76. [ISBN](/source/ISBN_(identifier)) [978-8-1713-3896-2](https://en.wikipedia.org/wiki/Special:BookSources/978-8-1713-3896-2).

---
Adapted from the Wikipedia article [Root cap](https://en.wikipedia.org/wiki/Root_cap) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Root_cap?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.