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			{{Short description\|Parts of plant enabling sexual reproduction}}
	{{db-meta\|HOAX!Plant sexuality? LOL - What's next? Planto-sexuals?}}
			]'' flower, showing part of the ] (specifically the ] and part of the ]) and the ]s that surround it]]

			'''Plant reproductive morphology''' is the study of the physical form and structure (the ]) of those parts of plants directly or indirectly concerned with ].
	{{{category\|]}}}

			Among all living organisms, ]s, which are the reproductive structures of ], are the most varied physically and show a correspondingly great diversity in methods of reproduction.<ref name="Barrett-2002"/> Plants that are not flowering plants (]e, ]es, ]s, ]s, ]s and ]s such as ]s) also have complex interplays between morphological adaptation and environmental factors in their sexual reproduction. The breeding system, or how the ] from one plant fertilizes the ] of another, depends on the reproductive morphology, and is the single most important determinant of the genetic structure of nonclonal plant populations. ] (1793) studied the reproduction of flowering plants and for the first time it was understood that the ] process involved both ] and ] interactions. ]'s theories of ] utilized this work to build his ], which includes analysis of the ] of flowers and their ] ]s.
	'''Plant sexuality''' deals with the wide variety of sexual reproduction systems found across the ] kingdom. That plants employ many different strategies to engage in sexual reproduction was used, from just a structural perspective, by ] (1735) to propose a system of classification of flowering plants, and later this subject received attention from ] (1877). ], the reproductive organs of ], are more varied than the equivalent structures of any other group of organisms, and flowering plants also have an unrivalled diversity of sexual systems (Barrett, 2002). But sexuality and the significance of sexual reproductive strategies is no less important in all of the other plant groups. The breeding system is the single most important determinant of the mating structure of nonclonal plant populations. The mating structure in turn controls the amount and distribution of genetic variation, a central element in the evolutionary process (Costich, 1995).

			== Use of sexual terminology ==
	== Terminology ==
			] gametophytes of the liverwort '']''. In this species, gametes are produced on different plants on umbrella-shaped ]s with different morphologies. The radiating arms of female gametophores (left) protect ] that produce eggs. Male gametophores (right) are topped with ] that produce sperm.]]

			Plants have complex lifecycles involving ]. One generation, the ], gives rise to the next generation, the ] asexually via ]s. Spores may be identical isospores or come in different sizes (]s and ]s), but strictly speaking, spores and sporophytes are neither male nor female because they do not produce ]s. The alternate generation, the gametophyte, produces gametes, ]s and/or ]. A gametophyte can be ] (bisexual), producing both eggs and sperm, or dioicous (unisexual), either female (producing eggs) or male (producing sperm).
	The complexity of the systems and devices used by plants to achieve sexual reproduction has resulted in botanists and evolutionary biologists proposing numerous terms to describe structures and strategies. Dellaporta and Calderon-Urrea (1993) list and define a variety of terms used to describe the modes of sexuality at different levels in flowering plants. This list is reproduced here (taken from Molner, 2004), generalized to fit more than just plants that have ]s, and expanded to include other terms and better definitions.

			In the ]s (]s, ]es, and ]s), the sexual gametophyte is the dominant generation. In ]s and ]s (including ]s, ]s, ]s, etc.) the sporophyte is the dominant generation; the obvious visible plant, whether a small herb or a large tree, is the sporophyte, and the gametophyte is very small. In bryophytes and ferns, the gametophytes are independent, free-living plants, while in seed plants, each female megagametophyte, and the megaspore that gives rise to it, is hidden within the sporophyte and is entirely dependent on it for nutrition. Each male gametophyte typically consists of two to four cells enclosed within the protective wall of a pollen grain.
	] is '''monoecious'''. Shown here: maturing male flower catkins on right, last year's female catkins on left]]
	*<big>Individual sexual organ</big> (a flower in angiosperms):
	** '''Bisexual''' - Reproductive organ with both male and female equivalent parts (stamens and pistil in angiosperms; also called a '''perfect''' flower); another term widely used is ''']'''.
	** '''Unisexual''' - Reproductive structure that is either functionally male or functionally female. In angiosperms this condition is also called '''imperfect'''.

			The sporophyte of a flowering plant is often described using sexual terms (e.g. "female" or "male") {{em\|based on the sexuality of the gametophyte it gives rise to}}. For example, a sporophyte that produces spores that give rise only to male gametophytes may be described as "male", even though the sporophyte itself is asexual, producing only spores. Similarly, flowers produced by the sporophyte may be described as "unisexual" or "bisexual", meaning that they give rise to either one sex of gametophyte or both sexes of the gametophyte.<ref name="Hickey-2001"/>{{pn\|date=March 2023}}
	*<big>Individual plant</big>:
	** '''Hermaphrodite''' - A plant that has only hermaphrodite reproductive structures. In angiosperm terminology a synonym is '''monoclinous''' from the ] "one bed".
	** '''Monoecious''' - having '''unisexual''' flowers, conifer cones, or functionally equivalent structures of both sexes appearing on the same plant; from Greek for "one household".
	** '''Dioecious''' - having '''unisexual''' flowers, conifer cones, or functionally equivalent structures occurring on different individuals; from Greek for "two households".
	** Because many dioecious ]s show a tendency towards monoecy (that is, a female plant may sometimes produce small numbers of male cones or vice versa), these species are termed '''subdioecious''' (McCormick & Andresen, 1963).
	** In angiosperm terminology, '''diclinous''' ("two beds") includes all species with unisexual flowers, although particularly those with ''only'' unisexual flowers, i.e. the monoecious and dioecious species.
	** '''Gynoecious''' - has only female reproductive structures; the "female" plant.
	** '''Androecious''' - has only male reproductive structures; the "male" plant.
	** '''Gynomonoecious''' - has both hermaphrodite and female structures.
	** '''Andromonoecious''' - has both hermaphrodite and male structures.
	** '''Trimonoecious''' (polygamous) - male, female, and hermaphrodite structures all appear on the same plant.

			==Flowering plants==
	] (''Ilex aquifolium'') is '''dioecious''': (above) shoot with flowers from male plant; (top right) male flower enlarged, showing ]s with ] and reduced, sterile ]; (below) shoot with flowers from female plant; (lower right) female flower enlarged, showing stigma <br>and reduced, sterile stamens with no pollen]]
	*<big>Plant population</big>
	** '''Hermaphrodite''' - only hermaphrodite plants.
	** '''Monoecious''' - only monoecious plants.
	** '''Dioecious''' - only dioecious plants.
	** '''Gynodioecious''' - both female and hermaphrodite plants present.
	** '''Androdioecious''' - both male and hermaphrodite plants present.
	** '''Trioecious''' (or '''subdioecious''') - male, female, and hermaphrodite plants are all in the same population.

			===Basic flower morphology===
	== Morphological mechanisms ==
			]'' flower]]

			The ] is the characteristic structure concerned with sexual reproduction in flowering plants (angiosperms). Flowers vary enormously in their structure (morphology). A ] flower, like that of '']'' shown in the figure, has a ] of outer ]s and a ] of inner ]s and both male and female ]s. The sepals and petals together form the ]. Next inwards there are numerous ]s, which produce ] grains, each containing a microscopic male gametophyte. Stamens may be called the "male" parts of a flower and collectively form the androecium. Finally in the middle there are ]s, which at maturity contain one or more ]s, and within each ovule is a tiny female gametophyte.{{sfn\|Sporne\|1974\|pp=14–15}} Carpels may be called the "female" parts of a flower and collectively form the gynoecium.
	=== Flower morphology ===
	A species, such as the ash (''Fraxinus excelsior'' L.), demonstrates the possible range of variation in morphology and functionality exhibited by flowers with respect to gender. Flowers of the ash are wind-pollinated and lack ]s and ]s. Structurally, the flowers may be either male, female, or hermaphrodite, the latter consisting of two anthers and an ovary ('c' below). A male flower can be morphologically male ('a' below) or a hermaphrodite flower with anthers and a rudimentary gynoecium ('b' below; functionally 'male'). Ash flowers can also be morphologically female ('e' below) or hermaphrodite and functionally female ('d' below; with vestigial anthers).

	] ] ]
	] ]

			Each carpel in ''Ranunculus'' species is an ] that produces one ovule,<ref name="Whittemore"/> which when fertilized becomes a seed. If the carpel contains more than one seed, as in '']'', it is called a ]. Two or more carpels may be fused together to varying degrees and the entire structure, including the fused ] and stigmas may be called a ]. The lower part of the pistil, where the ovules are produced, is called the ]. It may be divided into chambers (]s) corresponding to the separate carpels.{{sfn\|Sporne\|1974\|pp=125–127}}
	(Illustration from Binggeli and Power, 1999)

			===Variations===
	== Physiological mechanisms ==
			{{see also\|Flower#Floral function}}
	* ''See also:'' ], ]
			]'' has unisexual flowers and is ]. A pair of maturing male-flower catkins are on the right.]]
			]'' has unisexual flowers and is ]: (above and top right) a 'shoot' with flowers from a male plant, showing robust ]s with ], and a female-flower ], reduced and sterile; and (below and bottom right) a shoot with flowers from a female plant, showing a robust stigma and male-flower stamens (]s), reduced, sterile, with no pollen.]]

			A perfect flower has both stamens and carpels, and is described as "bisexual" or "hermaphroditic". A unisexual flower is one in which either the stamens or the carpels are missing, ] or otherwise non-functional. Each flower is either staminate (having only functional stamens and thus male), or carpellate or pistillate (having only functional carpels and thus female). If separate staminate and carpellate flowers are always found on the same plant, the species is described as '']''. If separate staminate and carpellate flowers are always found on different plants, the species is described as '']''.<ref name="Beentje-2010"/> A 1995 study found that about 6% of angiosperm species are dioecious, and that 7% of genera contain some dioecious species.<ref name="Renner-1995"/>
	== Evolution ==
	=== Angiosperms ===
	It is thought that flowering plants evolved from a common hermaphrodite ancestor, and that dioecy evolved from hermaphroditism. Hermaphroditism is very common in flowering plants—about 70% are hermaphroditic, while only about 5% are dioecious and 7% are monoecious. About 7% of species exhibit gynodioecy or androdioecy, while 10% contain both unisexual and bisexual flowers (Molner, 2004).

			Members of the birch family (]) are examples of monoecious plants with unisexual flowers. A mature alder tree ('']'' species) produces long catkins containing only male flowers, each with four stamens and a minute perianth, and separate stalked groups of female flowers, each without a perianth.{{sfn\|Stace\|2010\|pp=292–296}} (See the illustration of '']''.)
	A fair degree of correlation (though far from complete) exists between dioecy/sub-dioecy and plants that have seeds dispersed by ]s (both ] and ]). It is hypothesized that the concentration of fruit in half of the plants increases dispersal efficiency; female plants can produce a higher density of fruit as they do not expend resources on pollen production, and the dispersal agents (birds) need not waste time looking for fruit on male plants.

			Most hollies (members of the genus '']'') are dioecious. Each plant produces either functionally male flowers or functionally female flowers. In '']'' (see the illustration), the common European holly, both kinds of flower have four sepals and four white petals; male flowers have four stamens, female flowers usually have four non-functional reduced stamens and a four-celled ovary.{{sfn\|Stace\|2010\|p=669}} Since only female plants are able to set fruit and produce berries, this has consequences for gardeners. '']'' represents the first known group of flowering plants to separate from their common ancestor. It too is dioecious; at any one time, each plant produces either flowers with functional stamens but no carpels, or flowers with a few non-functional stamens and a number of fully functional carpels. However, ''Amborella'' plants may change their "sex" over time. In one study, five cuttings from a male plant produced only male flowers when they first flowered, but at their second flowering three switched to producing female flowers.<ref name="Buzgo-2004"/>
	==Cultivation of dioecious plants==
	] is famous for being dioecious, with only the female plant desirable for psychotropic effects. It is an interesting plant from a cultivational perspective because while the males are generally separated to prevent pollination of the female plants (undesirable for various reasons), the pheromones produced by the males cause the females to produce more ], making their unfertilized buds more potent. Experienced growers therefore learn to keep males near enough to the females to have this effect, but far enough that fertilization is unlikely. (Though obviously some females are allowed to be fertilized in order obtain seeds with which to re-populate the crop.)

			In extreme cases, almost all of the parts present in a complete flower may be missing, so long as at least one carpel or one stamen is present. This situation is reached in the female flowers of duckweeds ('']''), which consist of a single carpel, and in the male flowers of spurges ('']'') which consist of a single stamen.{{sfn\|Sporne\|1974\|pp=15–16}}
	== External link ==
			]
	* , vol. 4(4) (Winter 1996) at Wayne's Word.
			A species such as '']'', the common ash of Europe, demonstrates one possible kind of variation. Ash flowers are wind-pollinated and lack petals and sepals. Structurally, the flowers may be bisexual, consisting of two stamens and an ovary, or may be male (staminate), lacking a functional ovary, or female (carpellate), lacking functional stamens. Different forms may occur on the same tree, or on different trees.{{sfn\|Stace\|2010\|pp=292–296}} The Asteraceae (sunflower family), with close to 22,000 species worldwide, have highly modified inflorescences made up of flowers (florets) collected together into tightly packed heads. Heads may have florets of one sexual morphology – all bisexual, all carpellate or all staminate (when they are called ]), or may have mixtures of two or more sexual forms (heterogamous).<ref name="Barkley"/> Thus goatsbeards ('']'' species) have heads of bisexual florets, like other members of the tribe Cichorieae,<ref name="Barkley-2"/> whereas marigolds ('']'' species) generally have heads with the outer florets bisexual and the inner florets staminate (male).<ref name="Strother"/>

			Like ''Amborella'', some plants undergo sex-switching. For example, '']'' (Jack-in-the-pulpit) expresses sexual differences at different stages of growth: smaller plants produce all or mostly male flowers; as plants grow larger over the years the male flowers are replaced by more female flowers on the same plant. ''Arisaema triphyllum'' thus covers a multitude of sexual conditions in its lifetime: nonsexual juvenile plants, young plants that are all male, larger plants with a mix of both male and female flowers, and large plants that have mostly female flowers.<ref name="Ewing-1982"/> Other plant populations have plants that produce more male flowers early in the year and as plants bloom later in the growing season they produce more female flowers.{{citation needed\|date=March 2013}}
	== References ==
	* Barrett, S.C.H. 2002. The evolution of plant sexual diversity. ''Nature Reviews Genetics'' 3(4): 274-284.
	* Binggeli, P. and J. Power. 1999.
	* Costich, D. E. 1995. Gender specialization across a climatic gradient: experimental comparison of monoecious and dioecious ''Ecballium''. ''Ecology'', June 1995.
	* Darwin, C. 1877. ''The Different Forms of Flowers on Plants of the Same Species''.
	* Dellaporta, S.L. and A. Calderon-Urrea. 1993. Sex determination in flowering plants. ''The Plant Cell'', 5: 1241-1251
	* Linnaeus, C. 1735. '']''.
	* McCormick, J. & J. W. Andresen. 1963. A subdioecious population of ''Pinus cembroides'' in southeast Arizona. ''Ohio J. Science'', 63: 159-163.
	* Molnar, Sebastian. 2004. , internet version posted February 17, 2004.

			===Terminology===
	]
			{{anchor\|Terminology}}<!--Linked from ] -->
	]
			The complexity of the morphology of flowers and its variation within populations has led to a rich terminology.
	]
			* {{anchor\|Androdioecious}}'''Androdioecious''': having male flowers on some plants, bisexual ones on others.<ref name="Beentje-2010"/>
			* {{anchor\|Androecious}}'''Androecious''': having only male flowers (the male of a ] population); producing pollen but no seed.<ref name="Janick-2010"/>
			* '''Androgynous''': see ].<ref name="Beentje-2010"/>
			* {{anchor\|Androgynomonoecious}}'''Androgynomonoecious''': having male, female, and bisexual flowers on the same plant, also called trimonoecious.<ref name="Janick-2010">{{cite book \|author=Janick, J. \|year=2010 \|title=Plant Breeding Reviews \|publisher=Wiley \|isbn=9780470650028 \|url=https://books.google.com/books?id=by8K32RdKmYC}}</ref>
			* {{anchor\|Andromonoecious}}'''Andromonoecious''': having both ] and male flowers on the same plant.<ref name="Beentje-2010"/>
			* {{anchor\|Bisexual}}{{anchor\|Perfect flower}}{{anchor\|Androgynous}}{{anchor\|Hermaphroditic}}{{anchor\|Monoclinous}}{{anchor\|Synoecious}}'''Bisexual''': each flower of each individual has both male and female structures, i.e. it combines both sexes in one structure.<ref name="Beentje-2010"/> Flowers of this kind are called '''perfect''', having both ]s and ]s. Other terms used for this condition are '''androgynous''', '''hermaphroditic''', '''monoclinous''' and '''synoecious'''.
			* {{anchor\|Dichogamous}}'''Dichogamous''': having sexes developing at different times; producing pollen when the stigmas are not receptive,<ref name="Beentje-2010"/> either ] or ]. This promotes ] by limiting self-pollination.<ref name="Stace-1995"/> Some dichogamous plants have ] flowers, others have ] flowers.
			* '''Diclinous''': see ].<ref name="Beentje-2010"/>
			* {{anchor\|Dioecious}}''']''': having either only male or only female flowers.<ref name="Beentje-2010"/> No individual plant of the population produces both pollen and ovules.<ref name="Baskauf-2002"/> (From the Greek for "two households". See also the Wiktionary entry for {{linktext\|dioecious}}.)
			* {{anchor\|Gynodioecious}}'''Gynodioecious''': having hermaphrodite flowers and female flowers on separate plants.<ref>{{cite web\|url=http://botanydictionary.org/gynodioecious.html\|title=Gynodioecious\|publisher=Dictionary of Botany\|access-date=2013-04-10}}</ref>
			* {{anchor\|Gynoecious}}'''Gynoecious''': having only female flowers (the female of a ] population); producing seed but not pollen.<ref name="Grubben-2004">{{cite book\|author=G. J. H. Grubben\|title=Vegetables\|url=https://archive.org/details/bub_gb_6jrlyOPfr24C\|year=2004\|publisher=PROTA\|isbn=978-90-5782-147-9\|pages=–}}</ref>
			* {{anchor\|Gynomonoecious}}'''Gynomonoecious''': having both ] and female flowers on the same plant.<ref name="Beentje-2010"/>
			* '''Hermaphroditic''': see ].<ref name="Beentje-2010"/>
			* '''Homogamous:''' male and female sexes reach maturity in synchrony; producing mature pollens when stigma is receptive.
			* '''Imperfect''': (of flowers) having some parts that are normally present not developed,{{sfn\|Cook\|1968\|p=131}} e.g. lacking stamens. See also ].
			* '''Monoclinous''': see ].<ref name="Beentje-2010"/>
			* {{anchor\|Monoecious}}''']''': In the commoner narrow sense of the term, it refers to plants with ] flowers which occur on the same individual.<ref name="Hickey-2001"/> In the broad sense of the term, it also includes plants with ] flowers.<ref name="Beentje-2010"/> Individuals bearing separate flowers of both sexes at the same time are called simultaneously or synchronously monoecious and individuals that bear flowers of one sex at one time are called consecutively monoecious.<ref name="Kumar-2008">{{cite book\|author=Dinesh Kumar\|title=Definitional Glossary of Agricultural Terms\|url=https://books.google.com/books?id=P_ajeMQsNG8C&pg=PA115\|date=20 August 2008\|publisher=I. K. International Pvt Ltd\|isbn=978-81-906757-4-1\|pages=115–}}</ref> (From the Greek ''monos'' "single" + ''oikia'' "house". See also the Wiktionary entry for {{linktext\|monoecious}}.)
			* '''Perfect''': (of flowers) see ].<ref name="Beentje-2010"/>
			* {{anchor\|Polygamodioecious}}'''Polygamodioecious''': mostly ], but with either a few flowers of the opposite sex or a few ] flowers on the same plant.<ref name="Hickey-2001"/>
			* '''Polygamomonoecious''': see ].<ref name="Beentje-2010"/> Or, mostly monoecious, but also partly polygamous.<ref name="Hickey-2001"/>
			* {{anchor\|Polygamous}}{{anchor\|Polygamomonoecious}}{{anchor\|Trimonoecious}}'''Polygamous''': having male, female, and ] flowers on the same plant.<ref name="Beentje-2010"/> Also called '''polygamomonoecious''' or '''trimonoecious'''.<ref name="Geber-1999"/> Or, with bisexual and at least one of male and female flowers on the same plant.<ref name="Hickey-2001"/>
			* {{anchor\|Protandrous}}'''Protandrous''': (of ] plants) having male parts of flowers developed before female parts, e.g. having flowers that function first as male and then change to female or producing pollen before the stigmas of the same plant are receptive.<ref name="Beentje-2010"/> ('''Protoandrous''' is also used.)
			* {{anchor\|Protogynous}}'''Protogynous''': (of ] plants) having female parts of flowers developed before male parts, e.g. having flowers that function first as female and then change to male or producing pollen after the stigmas of the same plant are receptive.<ref name="Beentje-2010"/>
			* {{anchor\|Subandroecious}}'''Subandroecious''': having mostly male flowers, with a few female or ] flowers.<ref>{{cite journal \|last1=Testolin \|first1=R \|last2=Cipriani \|first2=G \|last3=Costa \|first3=G \|title=Sex segregation ratio and gender expression in the genus Actinidia \|journal=Sexual Plant Reproduction \|date=May 1995 \|volume=8 \|issue=3 \|doi=10.1007/BF00242255 \|s2cid=25414438 \|url=https://link.springer.com/article/10.1007/BF00242255 \|access-date=30 December 2020}}</ref>
			* {{anchor\|Subdioecious}}'''Subdioecious''': having some individuals in otherwise ] populations with flowers that are not clearly male or female. The population produces normally male or female plants with ] flowers, but some plants may have ] flowers, some both male and female flowers, and others some combination thereof, such as female and bisexual flowers. The condition is thought to represent a transition between bisexuality and ].<ref name="Olson-2000"/><ref name="Strittmatter-2002"/>
			* {{anchor\|Subgynoecious}}'''Subgynoecious''': having mostly female flowers, with a few male or ] flowers.{{citation needed\|date=February 2013}}
			* '''Synoecious''': see ].<ref name="Beentje-2010"/>
			* '''Trimonoecious''': see ]<ref name="Beentje-2010"/> and ].<ref name="Janick-2010"/>
			* ''']''': with male, female and bisexual flowers on different plants.<ref name="Beentje-2016"/>
			* {{anchor\|Unisexual}}{{anchor\|Diclinous}}{{anchor\|Incomplete flower}}{{anchor\|Imperfect flower}}'''Unisexual''': having either functionally male or functionally female flowers.<ref name="Beentje-2010"/> This condition is also called '''diclinous''', '''incomplete''' or '''imperfect'''.

			===Outcrossing===
	]
			{{More citations needed section\|date=June 2021}}
	]
			], cross-fertilization or allogamy, in which offspring are formed by the fusion of the ]s of two different plants, is the most common mode of reproduction among ]. About 55% of higher plant species reproduce in this way. An additional 7% are partially cross-fertilizing and partially self-fertilizing (autogamy). About 15% produce gametes but are principally self-fertilizing with significant out-crossing lacking. Only about 8% of higher plant species reproduce exclusively by non-sexual means. These include plants that reproduce vegetatively by runners or bulbils, or which produce seeds without embryo fertilization (]). The selective advantage of outcrossing appears to be the masking of deleterious recessive mutations.<ref name="Bernstein-1991"/>
	]

			The primary mechanism used by flowering plants to ensure outcrossing involves a genetic mechanism known as ]. Various aspects of floral morphology promote allogamy. In plants with bisexual flowers, the anthers and carpels may mature at different times, plants being ] (with the anthers maturing first) or protogynous (with the carpels mature first).{{citation needed\|date=March 2013}} Monoecious species, with unisexual flowers on the same plant, may produce male and female flowers at different times.{{citation needed\|date=March 2013}}

			Dioecy, the condition of having unisexual flowers on different plants, necessarily results in outcrossing, and probably evolved for this purpose. However, "dioecy has proven difficult to explain simply as an outbreeding mechanism in plants that lack self-incompatibility".<ref name="Renner-1995">{{cite journal \|last1=Renner \|first1=S.S. \|last2=Ricklefs \|first2=R.E. \|year=1995 \|title=Dioecy and its correlates in the flowering plants \|journal=American Journal of Botany \|volume=82 \|issue=5 \|pages=596–606 \|jstor=2445418 \|name-list-style=amp \|doi=10.2307/2445418\|url=https://epub.ub.uni-muenchen.de/14619/ }}</ref> Resource-allocation constraints may be important in the evolution of dioecy, for example, with wind-pollination, separate male flowers arranged in a catkin that vibrates in the wind may provide better pollen dispersal.<ref name="Renner-1995"/> In climbing plants, rapid upward growth may be essential, and resource allocation to fruit production may be incompatible with rapid growth, thus giving an advantage to delayed production of female flowers.<ref name="Renner-1995"/> Dioecy has evolved separately in many different lineages, and monoecy in the plant lineage correlates with the evolution of dioecy, suggesting that dioecy can evolve more readily from plants that already produce separate male and female flowers.<ref name="Renner-1995"/>

			== See also ==
			* ]
			* ]
			* ]
			* ]
			* ]
			* ]
			* ]
			* ]

			== References ==
			=== Citations ===
			{{Reflist\|30em\|refs=

			<ref name="Beentje-2010">{{Cite book \|last=Beentje \|first=Henk \|year=2010 \|title=The Kew Plant Glossary \|location=Richmond, Surrey \|publisher=] \|isbn=978-1-84246-422-9 }}</ref>

			<ref name="Beentje-2016">{{Cite book \|last=Beentje \|first=Henk \|year=2016 \|title=The Kew Plant Glossary \|edition=second \|location=Richmond, Surrey \|publisher=] \|isbn=978-1-84246-604-9 }}</ref>

			<ref name="Bernstein-1991">{{Cite book \|last1=Bernstein \|first1=C. \|last2=Bernstein \|first2=H. \|year=1991 \|title=Aging, Sex, and DNA Repair \|location=San Diego \|publisher=Academic Press \|isbn=978-0-12-092860-6 \|name-list-style=amp }}</ref>

			<ref name="Barrett-2002">{{Cite journal \|last=Barrett \|first=S.C.H. \|year=2002 \|title=The evolution of plant sexual diversity \|url=http://labs.eeb.utoronto.ca/barrett/pdf/schb_189.pdf \|journal=Nature Reviews Genetics \|volume=3 \|issue=4 \|pages=274–284 \|doi=10.1038/nrg776 \|pmid=11967552 \|s2cid=7424193 \|access-date=2013-02-26 \|archive-date=2013-05-27 \|archive-url=https://web.archive.org/web/20130527102011/http://labs.eeb.utoronto.ca/barrett/pdf/schb_189.pdf \|url-status=dead }}</ref>

			<ref name="Baskauf-2002">{{Cite web \|last=Baskauf \|first=Steve \|year=2002 \|url=http://www.cas.vanderbilt.edu/bioimages/pages/sexual-systems.htm \|title=Sexual systems in angiosperms \|access-date=2013-02-27 \|archive-url=https://web.archive.org/web/20180703153234/http://www.cas.vanderbilt.edu/bioimages/pages/sexual-systems.htm \|archive-date=2018-07-03 \|url-status=dead }}</ref>

			<ref name="Buzgo-2004">{{Cite journal \|last1=Buzgo \|first1=Matyas \|last2=Soltis \|first2=Pamela S. \|author-link2 = Pamela S. Soltis\|last3=Soltis \|first3=Douglas E. \|year=2004 \|title=Floral Developmental Morphology of ''Amborella trichopoda'' (Amborellaceae) \|journal=International Journal of Plant Sciences \|volume=165 \|issue=6 \|pages=925–947 \|doi=10.1086/424024 \|s2cid=84793812 \|name-list-style=amp }}</ref>

			<ref name="Ewing-1982">{{Cite journal \|last1=Ewing \|first1=J.W. \|last2=Klein \|first2=R.M. \|year=1982 \|title=Sex Expression in Jack-in-the-Pulpit \|journal=Bulletin of the Torrey Botanical Club \|volume=109 \|issue=1 \|pages=47–50 \|doi=10.2307/2484467 \|name-list-style=amp \|jstor=2484467 }}</ref>

			<ref name="Barkley">{{Cite book \|first1=Theodore M. \|last1=Barkley \|first2=Luc \|last2=Brouillet \|first3=John L. \|last3=Strother \|chapter=Asteraceae \|chapter-url = http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=10074 \|via=www.eFloras.org \|access-date=2013-03-04 \|name-list-style=amp \|title=Flora of North America}}</ref>

			<ref name="Barkley-2">{{Cite book \|first1=Theodore M. \|last1=Barkley \|first2=Luc \|last2=Brouillet \|first3=John L. \|last3=Strother \|chapter=Chichorieae \|chapter-url = http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=20701 \|via=www.eFloras.org \|access-date=2013-03-04 \|name-list-style=amp \|title=Flora of North America}}</ref>

			<ref name="Strother">{{Cite book \|first1=John L \|last1=Strother \|chapter=''Calendula'' \|chapter-url = http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=105062 \|via=www.eFloras.org \|access-date=2013-03-04 \|title=Flora of North America}}</ref>

			<ref name="Whittemore">{{Cite book \|first1=Alan T \|last1=Whittemore \|chapter=''Ranunculus'' \|chapter-url=http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=127971 \|via=www.eFloras.org \|access-date=2013-03-04 \|title=Flora of North America}}</ref>

			<ref name="Geber-1999">{{Cite book \|last=Geber \|first=Monica A. \|year=1999 \|title=Gender and sexual dimorphism in flowering plants \|url=https://books.google.com/books?id=pUo2T34ppKUC&q=polygamy+plants&pg=PA4 \|isbn=3-540-64597-7 \|publisher=Springer \|location=Berlin }} p. 4</ref>

			<ref name="Hickey-2001">{{Cite book\|last1=Hickey \|first1=M. \|last2=King \|first2=C. \|year=2001 \|title=The Cambridge Illustrated Glossary of Botanical Terms \|publisher=Cambridge University Press \|name-list-style=amp}}</ref>

			<ref name="Olson-2000">{{Cite journal \|last1=Olson \|first1=Matthew S. \|last2=Antonovics \|first2=Janis \|year=2000 \|title=Correlation between male and female reproduction in the subdioecious herb ''Astilbe biternata'' (Saxifragaceae) \|volume=87 \|issue=6 \|journal=American Journal of Botany \|pages=837–44 \|name-list-style=amp \|doi=10.2307/2656891\|jstor=2656891 \|pmid=10860914 }}</ref>

			<ref name="Stace-1995">{{Cite journal \|last=Stace \|first=H.M. \|year=1995 \|title=Protogyny, Self-Incompatibility and Pollination in ''Anthocercis gracilis'' (Solanaceae) \|doi=10.1071/BT9950451 \|journal=Australian Journal of Botany \|volume=43 \|issue=5 \|pages=451–459 }}</ref>

			<ref name="Strittmatter-2002">{{Cite journal\|last1=Strittmatter \|first1=L.I. \|last2=Negrón-Ortiz \|first2=V. \|last3=Hickey \|first3=R.J. \|year=2002 \|title=Subdioecy in ''Consolea spinosissima'' (Cactaceae): breeding system and embryological studies \|journal=American Journal of Botany \|volume=89 \|issue=9 \|pages=1373–1387 \|name-list-style=amp \|doi=10.3732/ajb.89.9.1373 \|pmid=21665739\|doi-access= }}</ref>

			<!--Not currently used but might be later <ref name=Vamo04>{{Cite journal \|last=Vamosi \|first=J.C. \|last2=Vamosi \|first2=S.M. \|year=2004 \|title=The role of diversification in causing the correlates of dioecy \|journal=Evolution \|volume=58 \|pages=723–731 \|doi=10.1554/03-312 \|name-list-style=amp }}</ref>-->

			}}

			=== Sources ===
			* {{cite book \|last=Cook \|first=J. Gordon \|year=1968 \|title=ABC of plant terms \|location=Watford, UK \|publisher=Merrow \|oclc=474319451 }}
			* {{Cite book \|last=Sporne \|first=K.R. \|year=1974 \|title=The Morphology of Angiosperms \|location=London \|publisher=Hutchinson \|isbn=978-0-09-120611-6 }}
			* {{cite book \|last=Stace \|first=Clive \|author-link = Clive Stace \|year=2010 \|title=New Flora of the British Isles \|edition=3rd \|location=Cambridge, UK \|publisher=Cambridge University Press \|isbn=978-0-521-70772-5 }}

			==Further reading==
			* {{Cite book \|last=Darwin \|first=Charles \|author-link=Charles Darwin\|year=1877 \|title=The Different Forms of Flowers on Plants of the Same Species \|location=London \|publisher=J. Murray}}
			* {{Cite book \|last=Linnaeus \|first=Carl \|author-link=Carl Linnaeus\|year=1735 \|title=Systema Naturae\|title-link=Systema Naturae }}
			* {{Cite book \|last=Sattler \|first=Rolf \|year=1973 \|title=Organogenesis of Flowers: a Photographic Text-Atlas \|publisher=University of Toronto Press \|isbn=978-0-8020-1864-9}}

			==External links==
			* {{Commons category-inline\|Plant reproductive morphology}}
			*

			{{Botany}}
			{{Sex (biology)}}

			]
			]

Latest revision as of 08:41, 9 December 2024

Parts of plant enabling sexual reproduction

Plant reproductive morphology is the study of the physical form and structure (the morphology) of those parts of plants directly or indirectly concerned with sexual reproduction.

Among all living organisms, flowers, which are the reproductive structures of angiosperms, are the most varied physically and show a correspondingly great diversity in methods of reproduction. Plants that are not flowering plants (green algae, mosses, liverworts, hornworts, ferns and gymnosperms such as conifers) also have complex interplays between morphological adaptation and environmental factors in their sexual reproduction. The breeding system, or how the sperm from one plant fertilizes the ovum of another, depends on the reproductive morphology, and is the single most important determinant of the genetic structure of nonclonal plant populations. Christian Konrad Sprengel (1793) studied the reproduction of flowering plants and for the first time it was understood that the pollination process involved both biotic and abiotic interactions. Charles Darwin's theories of natural selection utilized this work to build his theory of evolution, which includes analysis of the coevolution of flowers and their insect pollinators.

Use of sexual terminology

Plants have complex lifecycles involving alternation of generations. One generation, the sporophyte, gives rise to the next generation, the gametophyte asexually via spores. Spores may be identical isospores or come in different sizes (microspores and megaspores), but strictly speaking, spores and sporophytes are neither male nor female because they do not produce gametes. The alternate generation, the gametophyte, produces gametes, eggs and/or sperm. A gametophyte can be monoicous (bisexual), producing both eggs and sperm, or dioicous (unisexual), either female (producing eggs) or male (producing sperm).

In the bryophytes (liverworts, mosses, and hornworts), the sexual gametophyte is the dominant generation. In ferns and seed plants (including cycads, conifers, flowering plants, etc.) the sporophyte is the dominant generation; the obvious visible plant, whether a small herb or a large tree, is the sporophyte, and the gametophyte is very small. In bryophytes and ferns, the gametophytes are independent, free-living plants, while in seed plants, each female megagametophyte, and the megaspore that gives rise to it, is hidden within the sporophyte and is entirely dependent on it for nutrition. Each male gametophyte typically consists of two to four cells enclosed within the protective wall of a pollen grain.

The sporophyte of a flowering plant is often described using sexual terms (e.g. "female" or "male") based on the sexuality of the gametophyte it gives rise to. For example, a sporophyte that produces spores that give rise only to male gametophytes may be described as "male", even though the sporophyte itself is asexual, producing only spores. Similarly, flowers produced by the sporophyte may be described as "unisexual" or "bisexual", meaning that they give rise to either one sex of gametophyte or both sexes of the gametophyte.

Flowering plants

Basic flower morphology

The flower is the characteristic structure concerned with sexual reproduction in flowering plants (angiosperms). Flowers vary enormously in their structure (morphology). A perfect flower, like that of Ranunculus glaberrimus shown in the figure, has a calyx of outer sepals and a corolla of inner petals and both male and female sex organs. The sepals and petals together form the perianth. Next inwards there are numerous stamens, which produce pollen grains, each containing a microscopic male gametophyte. Stamens may be called the "male" parts of a flower and collectively form the androecium. Finally in the middle there are carpels, which at maturity contain one or more ovules, and within each ovule is a tiny female gametophyte. Carpels may be called the "female" parts of a flower and collectively form the gynoecium.

Each carpel in Ranunculus species is an achene that produces one ovule, which when fertilized becomes a seed. If the carpel contains more than one seed, as in Eranthis hyemalis, it is called a follicle. Two or more carpels may be fused together to varying degrees and the entire structure, including the fused styles and stigmas may be called a pistil. The lower part of the pistil, where the ovules are produced, is called the ovary. It may be divided into chambers (locules) corresponding to the separate carpels.

Variations

Terminology

The complexity of the morphology of flowers and its variation within populations has led to a rich terminology.

Androdioecious: having male flowers on some plants, bisexual ones on others.
Androecious: having only male flowers (the male of a dioecious population); producing pollen but no seed.
Androgynous: see bisexual.
Androgynomonoecious: having male, female, and bisexual flowers on the same plant, also called trimonoecious.
Andromonoecious: having both bisexual and male flowers on the same plant.
Bisexual: each flower of each individual has both male and female structures, i.e. it combines both sexes in one structure. Flowers of this kind are called perfect, having both stamens and carpels. Other terms used for this condition are androgynous, hermaphroditic, monoclinous and synoecious.
Dichogamous: having sexes developing at different times; producing pollen when the stigmas are not receptive, either protandrous or protogynous. This promotes outcrossing by limiting self-pollination. Some dichogamous plants have bisexual flowers, others have unisexual flowers.
Diclinous: see Unisexual.
Dioecious: having either only male or only female flowers. No individual plant of the population produces both pollen and ovules. (From the Greek for "two households". See also the Wiktionary entry for dioecious.)
Gynodioecious: having hermaphrodite flowers and female flowers on separate plants.
Gynoecious: having only female flowers (the female of a dioecious population); producing seed but not pollen.
Gynomonoecious: having both bisexual and female flowers on the same plant.
Hermaphroditic: see bisexual.
Homogamous: male and female sexes reach maturity in synchrony; producing mature pollens when stigma is receptive.
Imperfect: (of flowers) having some parts that are normally present not developed, e.g. lacking stamens. See also Unisexual.
Monoclinous: see bisexual.
Monoecious: In the commoner narrow sense of the term, it refers to plants with unisexual flowers which occur on the same individual. In the broad sense of the term, it also includes plants with bisexual flowers. Individuals bearing separate flowers of both sexes at the same time are called simultaneously or synchronously monoecious and individuals that bear flowers of one sex at one time are called consecutively monoecious. (From the Greek monos "single" + oikia "house". See also the Wiktionary entry for monoecious.)
Perfect: (of flowers) see bisexual.
Polygamodioecious: mostly dioecious, but with either a few flowers of the opposite sex or a few bisexual flowers on the same plant.
Polygamomonoecious: see polygamous. Or, mostly monoecious, but also partly polygamous.
Polygamous: having male, female, and bisexual flowers on the same plant. Also called polygamomonoecious or trimonoecious. Or, with bisexual and at least one of male and female flowers on the same plant.
Protandrous: (of dichogamous plants) having male parts of flowers developed before female parts, e.g. having flowers that function first as male and then change to female or producing pollen before the stigmas of the same plant are receptive. (Protoandrous is also used.)
Protogynous: (of dichogamous plants) having female parts of flowers developed before male parts, e.g. having flowers that function first as female and then change to male or producing pollen after the stigmas of the same plant are receptive.
Subandroecious: having mostly male flowers, with a few female or bisexual flowers.
Subdioecious: having some individuals in otherwise dioecious populations with flowers that are not clearly male or female. The population produces normally male or female plants with unisexual flowers, but some plants may have bisexual flowers, some both male and female flowers, and others some combination thereof, such as female and bisexual flowers. The condition is thought to represent a transition between bisexuality and dioecy.
Subgynoecious: having mostly female flowers, with a few male or bisexual flowers.
Synoecious: see bisexual.
Trimonoecious: see polygamous and androgynomonoecious.
Trioecious: with male, female and bisexual flowers on different plants.
Unisexual: having either functionally male or functionally female flowers. This condition is also called diclinous, incomplete or imperfect.

Outcrossing

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Outcrossing, cross-fertilization or allogamy, in which offspring are formed by the fusion of the gametes of two different plants, is the most common mode of reproduction among higher plants. About 55% of higher plant species reproduce in this way. An additional 7% are partially cross-fertilizing and partially self-fertilizing (autogamy). About 15% produce gametes but are principally self-fertilizing with significant out-crossing lacking. Only about 8% of higher plant species reproduce exclusively by non-sexual means. These include plants that reproduce vegetatively by runners or bulbils, or which produce seeds without embryo fertilization (apomixis). The selective advantage of outcrossing appears to be the masking of deleterious recessive mutations.

The primary mechanism used by flowering plants to ensure outcrossing involves a genetic mechanism known as self-incompatibility. Various aspects of floral morphology promote allogamy. In plants with bisexual flowers, the anthers and carpels may mature at different times, plants being protandrous (with the anthers maturing first) or protogynous (with the carpels mature first). Monoecious species, with unisexual flowers on the same plant, may produce male and female flowers at different times.

Dioecy, the condition of having unisexual flowers on different plants, necessarily results in outcrossing, and probably evolved for this purpose. However, "dioecy has proven difficult to explain simply as an outbreeding mechanism in plants that lack self-incompatibility". Resource-allocation constraints may be important in the evolution of dioecy, for example, with wind-pollination, separate male flowers arranged in a catkin that vibrates in the wind may provide better pollen dispersal. In climbing plants, rapid upward growth may be essential, and resource allocation to fruit production may be incompatible with rapid growth, thus giving an advantage to delayed production of female flowers. Dioecy has evolved separately in many different lineages, and monoecy in the plant lineage correlates with the evolution of dioecy, suggesting that dioecy can evolve more readily from plants that already produce separate male and female flowers.

References

Citations

Barrett, S.C.H. (2002). "The evolution of plant sexual diversity" (PDF). Nature Reviews Genetics. 3 (4): 274–284. doi:10.1038/nrg776. PMID 11967552. S2CID 7424193. Archived from the original (PDF) on 2013-05-27. Retrieved 2013-02-26.
^ Hickey, M. & King, C. (2001). The Cambridge Illustrated Glossary of Botanical Terms. Cambridge University Press.
Sporne 1974, pp. 14–15.
Whittemore, Alan T. "Ranunculus". Flora of North America. Retrieved 2013-03-04 – via www.eFloras.org.
Sporne 1974, pp. 125–127.
^ Beentje, Henk (2010). The Kew Plant Glossary. Richmond, Surrey: Royal Botanic Gardens, Kew. ISBN 978-1-84246-422-9.
^ Renner, S.S. & Ricklefs, R.E. (1995). "Dioecy and its correlates in the flowering plants". American Journal of Botany. 82 (5): 596–606. doi:10.2307/2445418. JSTOR 2445418.
^ Stace 2010, pp. 292–296.
Stace 2010, p. 669.
Buzgo, Matyas; Soltis, Pamela S. & Soltis, Douglas E. (2004). "Floral Developmental Morphology of Amborella trichopoda (Amborellaceae)". International Journal of Plant Sciences. 165 (6): 925–947. doi:10.1086/424024. S2CID 84793812.
Sporne 1974, pp. 15–16.
Barkley, Theodore M.; Brouillet, Luc & Strother, John L. "Asteraceae". Flora of North America. Retrieved 2013-03-04 – via www.eFloras.org.
Barkley, Theodore M.; Brouillet, Luc & Strother, John L. "Chichorieae". Flora of North America. Retrieved 2013-03-04 – via www.eFloras.org.
Strother, John L. "Calendula". Flora of North America. Retrieved 2013-03-04 – via www.eFloras.org.
Ewing, J.W. & Klein, R.M. (1982). "Sex Expression in Jack-in-the-Pulpit". Bulletin of the Torrey Botanical Club. 109 (1): 47–50. doi:10.2307/2484467. JSTOR 2484467.
^ Janick, J. (2010). Plant Breeding Reviews. Wiley. ISBN 9780470650028.
Stace, H.M. (1995). "Protogyny, Self-Incompatibility and Pollination in Anthocercis gracilis (Solanaceae)". Australian Journal of Botany. 43 (5): 451–459. doi:10.1071/BT9950451.
Baskauf, Steve (2002). "Sexual systems in angiosperms". Archived from the original on 2018-07-03. Retrieved 2013-02-27.
"Gynodioecious". Dictionary of Botany. Retrieved 2013-04-10.
G. J. H. Grubben (2004). Vegetables. PROTA. pp. 255–. ISBN 978-90-5782-147-9.
Cook 1968, p. 131.
Dinesh Kumar (20 August 2008). Definitional Glossary of Agricultural Terms. I. K. International Pvt Ltd. pp. 115–. ISBN 978-81-906757-4-1.
Geber, Monica A. (1999). Gender and sexual dimorphism in flowering plants. Berlin: Springer. ISBN 3-540-64597-7. p. 4
Testolin, R; Cipriani, G; Costa, G (May 1995). "Sex segregation ratio and gender expression in the genus Actinidia". Sexual Plant Reproduction. 8 (3). doi:10.1007/BF00242255. S2CID 25414438. Retrieved 30 December 2020.
Olson, Matthew S. & Antonovics, Janis (2000). "Correlation between male and female reproduction in the subdioecious herb Astilbe biternata (Saxifragaceae)". American Journal of Botany. 87 (6): 837–44. doi:10.2307/2656891. JSTOR 2656891. PMID 10860914.
Strittmatter, L.I.; Negrón-Ortiz, V. & Hickey, R.J. (2002). "Subdioecy in Consolea spinosissima (Cactaceae): breeding system and embryological studies". American Journal of Botany. 89 (9): 1373–1387. doi:10.3732/ajb.89.9.1373. PMID 21665739.
Beentje, Henk (2016). The Kew Plant Glossary (second ed.). Richmond, Surrey: Royal Botanic Gardens, Kew. ISBN 978-1-84246-604-9.
Bernstein, C. & Bernstein, H. (1991). Aging, Sex, and DNA Repair. San Diego: Academic Press. ISBN 978-0-12-092860-6.

Sources

Cook, J. Gordon (1968). ABC of plant terms. Watford, UK: Merrow. OCLC 474319451.
Sporne, K.R. (1974). The Morphology of Angiosperms. London: Hutchinson. ISBN 978-0-09-120611-6.
Stace, Clive (2010). New Flora of the British Isles (3rd ed.). Cambridge, UK: Cambridge University Press. ISBN 978-0-521-70772-5.

External links

Media related to Plant reproductive morphology at Wikimedia Commons
Images of sexual systems in flowering plants at bioimages.vanderbilt.edu

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