Accessory fruit

An accessory fruit is a fruit that contains tissue derived from plant parts other than the ovary. In other words, the flesh of the fruit develops not from the floral ovary, but from some adjacent tissue exterior to the carpel (for example, from receptacles or sepal). As a general rule, the accessory fruit is a combination of several floral organs, including the ovary. In contrast, true fruit forms exclusively from the ovary of the flower.[1]

"False fruit" redirects here. For artificial fruit, see Food model.
A selection of accessory fruits (from left to right: pear, fig, and strawberry)

Accessory fruits are usually indehiscent, meaning fruits that do not split open to release seeds when they have reached maturity.[2]

Terminology

Alternative terms for accessory fruit are false fruit, spurious fruit, pseudofruit, or pseudocarp. These are older terms for accessory fruit that have been criticized as "inapt",[1] and are not used by some botanists today.

Incorporated organs
See also: Glossary of botanical terms

The following are examples of accessory fruits listed by the plant organ from which the accessory tissue is derived:[3]

Accessory Fruit Organs
OrganFruit
Hypanthiumapple, pear
Involucrepineapple
Pedunclecashew apple
Perianthanthocarps of the Nyctaginaceae
Receptaclefig, mulberry, pineapple, strawberry
Calyxeastern teaberry, rose apple

Fruit with fleshy seeds, such as pomegranate or mamoncillo, are not considered to be accessory fruits.[4]

Examples

Apples and pears
Apple section, showing seeds plus papery expression of the ovary, surrounded by tissue formed from ripening of the hypanthium

The part of apples and pears that is consumed is, in fact, the hypanthium. The ovary is the papery core that surrounds the apple seeds. As the hypanthium ripens it forms the edible tissues. [5]

Roses

For roses, the hypanthium is the tissue that composes the edible part of rosehips. Roses and apples are both members of the Rosaceae family; the fact that they have similar fruit morphology is a major consideration in placing them in the same taxonomic family.[5]

Strawberries
On this strawberry, the many pips located on the surface have germinated. The pips of the strawberry are its true fruit.

The edible part of the strawberry is formed, as part of the ripening process, from the receptacle of the strawberry flower. The true fruits (hence, containing the seeds) are the roughly 200 pips (which are, technically, achenes, a true fruit that contains a single seed from a single ovary). These pips dot the exterior of the strawberry.[6]

Cashew apple
The cashew ‘apple’ and its attached drupe, which contains the edible seed

The cashew apple is an oval- or pear-shaped structure that develops from the pedicel and the receptacle of the cashew flower and is technically called a hypocarpium.[7][8][9] It ripens into a yellow or red structure about 5–11 cm (2–4+1⁄4 in) long.[10][8] The true fruit of the cashew tree is a kidney–shaped drupe that grows at the end of the cashew apple; the seed inside this drupe is the cashew nut of commerce.[11]

Pineapple
Pineapple in flower

The pineapple is formed when 50 to 200 unpollinated flowers coalesce in a spiral arrangement— the flowers form individually and then fuse as a single 'multiple fruit'. The ovaries develop into berries and the fruit forms around an intercalary spike. The intercalary inflorescence (cluster of flowers) results when the terminal cluster of flowers are left behind by the growth of the main axis of the plant. Each polygonal area on the pineapple's surface is an individual flower.[12]

Research

Current research has proposed that a single class of genes may be responsible for regulating accessory fruit formation and ripening.[13] A study using strawberries concluded that hormone signaling pathways involving gibberellic acid and auxin affect gene expression, and contribute to the initiation of accessory fruit development.[6] Metabolic modifications in different developing accessory fruit tissues are due to the varied distributions of compounds such as triterpenoids and steroids.[14]

See also

References
  1. Esau, K. 1977. Anatomy of seed plants. John Wiley and Sons, New York.
  2. "Glossary Details – The William & Lynda Steere Herbarium". sweetgum.nybg.org. Retrieved 2021-03-17.
  3. Merriam Webster Collegiate Dictionary entries for syconium, accessory fruit, core, and strawberry, Merriam-Webster, Inc., 2006
  4. Holland, D.; Hatib, K.; Bar-Ya'akov, I. (2009), "Pomegranate: Botany, Horticulture, Breeding", Horticultural Reviews, John Wiley & Sons, Ltd, pp. 127–191, doi:10.1002/9780470593776.ch2, ISBN 978-0-470-59377-6, retrieved 2021-11-28
  5. Michaels, Tom; Clark, Matt; Hoover, Emily; Irish, Laura; Smith, Alan; Tepe, Emily (2022-06-20). "8.1 Fruit Morphology". {{cite journal}}: Cite journal requires |journal= (help)
  6. Zhou, Junhui; Sittmann, John; Guo, Lei; Xiao, Yuwei; Huang, Xiaolong; Pulapaka, Anuhya; Liu, Zhongchi (March 2021). "Gibberellin and auxin signaling genes RGA1 and ARF8 repress accessory fruit initiation in diploid strawberry". Plant Physiology. 185 (3): 1059–1075. doi:10.1093/plphys/kiaa087. PMC 8133647. PMID 33793929.
  7. Varghese, T.; Pundir, Y. (1964). "Anatomy of the pseudocarp in Anacardium occidentale L.". Proceedings of the Indian Academy of Sciences, Section B. 59 (5): 252–258. doi:10.1007/BF03052341. S2CID 83230755.
  8. James A Duke (1983). "Anacardium occidentale L." Handbook of Energy Crops. (unpublished); In: NewCROP, New Crop Resource Online Program, Center for New Crops and Plant Products, Purdue University. Retrieved 10 December 2019.
  9. "Cashew". Encyclopedia Britannica. 7 April 2020. Retrieved 8 May 2021.
  10. Morton, Julia F. (1987). Cashew apple, Anacardium occidentale L. pp. 239–240. ISBN 978-0-9610184-1-2. Archived from the original on 15 March 2007. Retrieved 18 March 2007. {{cite book}}: |work= ignored (help)
  11. Morton, Julia F. (1987). Cashew apple, Anacardium occidentale L. pp. 239–240. ISBN 978-0-9610184-1-2. Archived from the original on 15 March 2007. Retrieved 18 March 2007. {{cite book}}: |work= ignored (help)
  12. "Plant Details - Information about Ananas comosus Plant". www.efloraofgandhinagar.in. Retrieved 2023-03-18.
  13. Ireland, Hilary; Yao, Jia-Long; Tomes, Sumathi; Sutherland, Paul; Nieuwenhuizen, Niels; Gunaseelan, Kularajathevan; Winz, Robert; David, Karine; Schaffer, Robert (13 December 2012). "Apple SEPALLATA1/2-like genes control fruit flesh development and ripening". The Plant Journal. 73 (6): 1004–1056. doi:10.1111/tpj.12094. PMID 23236986.
  14. Dashbaldan, Soyol; Rogowska, Agata; Pączkowski, Cezary; Szakiel, Anna (25 August 2021). "Distribution of Triterpenoids and Steroids in Developing Rugosa Rose (Rosarugosa Thunb.) Accessory Fruit". Molecules. 26 (17): 5158. doi:10.3390/molecules26175158. PMC 8433923. PMID 34500591.
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