Sexual system in seed plants
Monoecy (; adj. monoecious )
[1] is a
sexual system in
seed plants where separate
male and
female cones or flowers are present on the same plant.
[2] It is a monomorphic
sexual system comparable with
gynomonoecy ,
andromonoecy and
trimonoecy , and contrasted with
dioecy where individual plants produce cones or flowers of only one sex and with bisexual or hermaphroditic plants in which male and female gametes are produced in the same flower.
[3]
Monoecy often co-occurs with
anemophily ,
[2] because it prevents
self-pollination of individual flowers and reduces the probability of self-pollination between male and female flowers on the same plant.
[4] : 32
Monoecy in
angiosperms has been of interest for
evolutionary biologists since
Charles Darwin .
[5]
Terminology
Monoecious comes from the Greek words for one house.
[6]
History
The term monoecy was first introduced in 1735 by
Carl Linnaeus .
[2]
Darwin noted that the flowers of monoecious species sometimes showed traces of the opposite sex function, suggesting that they evolved via hermaphroditism.
[7] Monoecious
hemp was first reported in 1929.
[8]
Occurrence
Monoecy is most common in
temperate climates
[9] and is often associated with inefficient pollinators or
wind-pollinated plants.
[10]
[11] It may be beneficial to reducing pollen-stigma interference,[
clarification needed ] thus increasing seed production.
[12]
Around 10% of all
seed plant species are monoecious.
[9] It is present in 7% of
angiosperms .
[4] : 8 Most
Cucurbitaceae are monoecious
[13] including most
watermelon
cultivars .
[14] It is prevalent in
Euphorbiaceae .
[15]
[16] Dioecy is replaced by monoecy in the polyploid subspecies of
Empetrum nigrum ,
E. nigrum ssp. hermaphroditum and polyploid populations of
Mercurialis annua .
[17]
Maize
Maize is monoecious since both
pistillate (female) and
stamenate (male) flowers occur on the same plant. The pistillate flowers are present on the ears of corn and the stamenate flowers are in the tassel at the top of the stalk. In the
ovules of the pistillate flowers,
diploid cells called megaspore mother cells undergo
meiosis to produce haploid
megaspores . In the anthers of the stamenate flowers, diploid
pollen mother cells undergo meiosis to produce pollen grains. Meiosis in maize requires gene product
RAD51 , a protein employed in
recombinational repair of
DNA double-strand breaks .
[18]
Evolution
The evolution of monoecy has received little attention.
[7]
Male and female flowers evolve from hermaphroditic flowers
[19] via
andromonoecy or
gynomonoecy .
[20] : 148
In
amaranths monoecy may have evolved from hermaphroditism through various processes caused by male sterility genes and female fertility genes.
[20] : 150
Monoecy may be an intermediate state between hermaphroditism and dioecy.
[21] Evolution from dioecy to monoecy probably involves
disruptive selection on floral sex ratios.
[22] : 65 Monoecy is also considered to be a step in the evolutionary pathway from
hermaphroditism towards dioecy.
[23] : 91 Some authors even argue monoecy and dioecy are related.
[2] But, there is also evidence that monoecy is a pathway from
sequential hermaphroditism to dioecy.
[23] : 8
See also
References
^
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^
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b
c
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^ Torices, Rubén; Méndez, Marcos; Gómez, José María (2011).
"Where do monomorphic sexual systems fit in the evolution of dioecy? Insights from the largest family of angiosperms" . New Phytologist . 190 (1): 234–248.
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^ Nozaki, Hisayoshi; Mahakham, Wuttipong; Heman, Wirawan; Matsuzaki, Ryo; Kawachi, Masanobu (2020-07-02).
"A new preferentially outcrossing monoicous species of Volvox sect. Volvox (Chlorophyta) from Thailand" . PLOS ONE . 15 (7): e0235622.
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^
a
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^ Glover, Beverley (February 2014).
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^ Friedman, Janice; Barrett, Spencer C. H. (January 2009).
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^ Patiny, Sébastien (2011-12-08).
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^ Pessarakli, Mohammad (2016-02-22).
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^ Prohens-Tomás, Jaime; Nuez, Fernando (2007-12-06).
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^ Webster, G. L. (2014). "Euphorbiaceae". In Kubitzki, Klaus (ed.). The Families and Genera of Vascular Plants - Volume XI - Flowering Plants, Eudicots - Malpighiales .
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^ Bahadur, Bir; Sujatha, Mulpuri; Carels, Nicolas (2012-12-14).
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^ Volz, Stefanie M.; Renner, Susanne S. (2008).
"Hybridization, polyploidy and evolutionary transitions between monoecy and dioecy in Bryonia (Cucurbitaceae)" . American Journal of Botany . 95 (10): 1297–1306.
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^ Li J, Harper LC, Golubovskaya I, Wang CR, Weber D, Meeley RB, McElver J, Bowen B, Cande WZ, Schnable PS. Functional analysis of maize RAD51 in meiosis and double-strand break repair. Genetics. 2007 Jul;176(3):1469-82. doi: 10.1534/genetics.106.062604. Epub 2007 May 16. PMID: 17507687; PMCID: PMC1931559
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