Radicle

In botany, the radicle is the first part of a seedling to emerge from the seed, during the process of germination. [1] Germination understood as a biomechanical process describes the radicle with the hypocotyl combined as the embryonic axis in the seed. [2] The radicle emerges from a seed through the micropyle.

The emergence of the radicle is either the end or terminal part [3] (2nd of 2 phases [4] (or) 3rd of 3 phases [5][6]) or the 5th of 9 stages [7][lower-alpha 1] of germinating.

The radicle is the embryonic root of the plant, [1] and grows downward in the soil [8] (positive geotropism). [9] The radicle absorbs water and nutrients from the soil [10]

Radicles are classified into two main types. Those pointing away from the seed coat scar or hilum are classified as antitropous, and those pointing towards the hilum are syntropous.

If the radicle begins to decay, the seedling undergoes pre-emergence damping off. This disease appears on the radicle as darkened spots. Eventually, it causes death of the seedling.

In 1880, Charles Darwin published a book about plants he had studied, The Power of Movement in Plants, where he mentions the radicle.

> It is hardly an exaggeration to say that the tip of the radicle thus endowed [..] acts like the brain of one of the lower animals; the brain being situated within the anterior end of the body, receiving impressions from the sense-organs, and directing the several movements.

## See also

* Plant perception (physiology)

## Note

1. ↑ within the BBCH-scale [7]

## References

1. ↑ 1.0 1.1 "New to the Glossary: Root, Radicle, Primary Root". Virginia Cooperative Extension: Virginia Tech, Virginia State University, U.S. Department of Agriculture. November 2024. https://mgnv.org/illustrated-glossary/new-to-the-glossary-root-radicle-primary-root/.
2. ↑ Tina Steinbrecher; Gerhard Leubner-Metzger (1 Feb 2017). "The biomechanics of seed germination". J Exp Bot 68 (4): Abstract. doi:10.1093/jxb/erw428. PMID 27927995. https://pubmed.ncbi.nlm.nih.gov/27927995/https://pubmed.ncbi.nlm.nih.gov/27927995/.
3. ↑ Kent J. Bradford (4 January 1995). "Water Relations in Seed Germination". Seed Development and Germination Volume 41. Taylor & Francis. p. 355 (E.Hydration/Dehydration Cycles). ISBN 9780824792299. https://books.google.com/books?id=AHVDtveqlpMC.
4. ↑ Lalit M. Srivastava (2002). "Seed Germination, Mobilization of Food Reserves, and Seed Dormancy". Plant Growth and Development Hormones and Environment. Academic Press. pp. 448-449 (Section I. Seed Germnation 1. Imbibition of Water 2. Radicle Growth and Penetration of Testa). ISBN 9780080514031. https://books.google.com/books?id=wXLBKdncciQC&dq=plant+germination+radicle&pg=PA449.
5. ↑ Edward Francis Durner (2013). "Physiology of Growth in Specific Organs: Flowers, Fruit, and Seeds". Principles of Horticultural Physiology. CABI. p. 80 (Imbibition). ISBN 9781780643069. https://books.google.com/books?id=oc9mQU3Z0AAC&dq=germination+radicle&pg=PA81. "Water imbibition is the first step of germination (Nonogaki et al. 2010). Water uptake by seeds is triphasic. There is a rapid initial uptake of water (phase I) followed by a plateau phase (phase II). A third phase (phase III) involves the rapid uptake of water with elongation of the embryonic axis which results in radicle emergence and the completion of germination."
6. ↑ Choi, J.-Y.; Ju, Y.-H.; Nakamichi, A.; Cho, S.-W.; Woo, S.-H.; Sakagami, J.-I. (2024). "Effect of Seed Hydropriming on the Elongation of Plumule and Radicle During the Germination Process and Changes in Enzyme Activity Under Water-Deficient Conditions: 1. Introduction". Plants (MDPI) 13 (3537). doi:10.3390/plants13243537.
7. ↑ 7.0 7.1 Mábele de Cássia Ferreira; Fabrina Bolzan Martins; Haroldo Felipe da Costa (22 October 2025). "Phenological description for the initial development stage of five Brazilian native forest species according to BBCH scale - 2.2 Adapting the BBCH scale for five native Brazilian forest species TABLE 3.". Annals of Applied Biology (John Wiley & Sons, Inc). doi:10.1111/aab.70071. https://onlinelibrary.wiley.com/doi/10.1111/aab.70071.
8. ↑ "radicle | plant anatomy" (in en). Encyclopedia Britannica. https://www.britannica.com/science/radicle.
9. ↑ Herbert Edward Street; Helgi Öpik (1976). "Chapter 1: The Plant and Its Environment". The Physiology of Flowering Plants Their Growth and Development. Edward Arnold. p. 12. ISBN 9780713125283. https://books.google.com/books?id=2JEpAQAAMAAJ&q=radicle+geotropic.
10. ↑ Molly Jameson (February 1, 2024). "The Science of Germination". Wordpress. https://nwdistrict.ifas.ufl.edu/hort/2024/02/01/the-science-of-germination/.

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