MALVACEAE INFO

Biology: Reproductive Biology: Distribution of Sexes

Distribution of Sexes between Flowers

A flower may be either male, androus or staminate (with fertile stamens, but lacking fertile pistils), female, gynous, carpellate or pistillate (with fertile pistils but lacking fertile stamens), hermaphodite, bisexual, synoecious, monoclinous, homoecious or perfect (with both fertile pistils and stamens) or sterile, neuter, neutral or agamous (with neither fertile pistils nor stamens). Male and female flowers collectively are unisexual or imperfect. Female and hermaphrodite flowers collectively are fertile. Male and sterile flowers collectively are barren.

Note: The plant life cycle incorporates an alternation of generations between the macroscopic diploid sporophyte and the microscopic haploid gametophytes, which in flowering plants are the embryo sac (female) and pollen grain (male). Strictly speaking sporophytes, and their flowers and inflorescences are neither male nor fermale. If one wished to avoid the arguably incorrect usage of male and female, the most commonly used alternative is staminate and pistillate.

Distribution of Sexes within Inflorescences

When an inflorescence contains just one type of flower the same term can be used for the inflorescence as for the flowers of which it is composed. (But note that an inflorescence composed of synoecious (hermaphrodite) flowers is not a synoecious inflorescence.)

When an inflorescence contains two or more types of flower, then there are a number of terms describing the types and positions of the flowers; an inflorescence with sterile flowers inside or above and male flowers outside or below is agamandrous, one with sterile flowers inside or above and female flowers outside or below is agamogynous, one with sterile flowers inside or above and hermaphrodite flowers outside or below is agamohermaphroditic, one with male flowers inside or above and female flowers outside of below is androgynous, one with male flowers inside or above and sterile flowers outside or below is andragamous, one with male flowers inside or above and hermaphrodite flowers outside or below is androhermaphroditic, one with female flowers inside or above and male flowers outside of below is gynecandrous, one with female flowers inside or above and sterile flowers outside or below is gynagamous, one with female flowers inside or above and hermaphrodite flowers outside or below is gynehermaphroditic, one with hermaphrodite flowers inside or above and male flowers outside of below is hermaphrodandrous, one with hermaphrodite flowers inside or above and sterile flowers outside or below is hermaphrodagamous, one with hermaphrodite flowers inside or above and female flowers outside or below is hermaphrodigynous. An inflorescence with male flowers above and below and female flowers in the middle is androgynecandrous. Specific terms for particular forms of inflorescence have been used, e.g. agamandrocephalous, agamohermaphrodicephalous [2]

Inflorescences containing both male and female flowers, including androgynous, gynecandrous and androgynecandrous inflorescences, are synoecious inflorescences.

Distribution of Sexes between Inflorescences

In a plant which bears more than one type of flower there may be one type of inflorescence, in which case it may be described as homosexual, or there may be more than one type of inflorescence, in which case it may be described as heterosexual. Specific terms for particular forms of inflorescence have been used e.g. homocephalous and heterocephalous for capitula, homocymous and heterocymous for cymes, and homospicous and heterospicous for spikes, and parallel terms could be used for other inflorescence types. [2]

Distribution of Sexes in Plants

Flowers of the 4 types can be distributed among plants is various ways. In principle there are 16 possible combinations of flower types on an individual plant. In reality, not all of these occur, and names do not exist for all these states.

A plant which bears no flowers or only sterile flowers is sterile; a sterile plant can still reproduce vegetatively, e.g. by rhizomes, stolons, bulbils, plantlets, etc. A plant which bears only male flowers is male or androecious; a plant which bears only female flowers is female or gynoecious; a plant which bears only hermaphrodite flowers is synoecious, or monoclinous..

A plant which bears both unisexual and hermaphrodite flowers is polygamous. A plant which bears mostly male flowers, but with a small proportion of female or hermaphrodite flowers is subandroecious. A plant which bears mostly female flowers, but with a small proportion of male or hermaphrodite flowers is subgynoecious. A plant which bears mostly hermaphrodite flowers, but with a small proportion of male or female flowers is subhermaphrodite.

A plant which bears male and female flowers is monoecious or cosexual, a plant which bears male and hermaphrodite flowers is andromonoecious or polygamandroecious (unattested), and a plant which bears female and hermaphrodite flowers is gynomonoecious or polygamogynooecious. A plant which bears male, female and hermaphrodite flowers is trimonoecious or androgynomonoecious. A plant which bears hermaphrodite and male or female or both male and female flowers is polygamomonoecious

A plant which bears sterile and hermaphrodite flowers is agamohermaphrodite, one which bears sterile and female flowers is agamogynaecious, and one which bears sterile and male flowers is agamandroecious. One which bears sterile, female and hermaphrodite flowers is agamogynomonoecious. Terms for the other three combinations are unattested, but using parallel constructions would be agamandromonoecious for plants bearing sterile, male and hermaphrodite flowers, agamomonoecious for plants bearing male, female and sterile flowers, and agamotrimonoecious for plants bearing all for types of flowers.

Distribution of Sexes in Populations and Species (Sexual Systems)

A sexual system or breeding system is a combination of the 16 possible types of plant

Populations and species may display various combinations of the 16 possible types of plant. 65,536 combinations are possible, but some are only possible in vegetatively reproducing plants, and others are only possible in asexually reproducing plants. In practice the great majority of populations and species have one, two or three types of plant.

Populations and species in which each plant bears a single type of flower may be dioecious (male and female flowers borne on separate plants), androdioecious (male and hermaphrodite flowers borne on separate plants), gynodioecious (female and hermaphrodite flowers borne on separate plants) or trioecious or dioeciopolygamous (male, female and hermaphrodite flowers borne on separate plants).

Populations and species in which all plants bear the same types of flowers are synoecious, monoclinous, homoecious or hermaphrodite (when each plant bears solely hermaphrodite flowers), monoecious (when each plant bears both male and female flowers), andromonoecious (when each plant bears male and hermaphrodite flowers), gynomonoecious (when each plant bears female and hermaphrodite flowers), agamohermaphrodite (when each plant bears neuter and hermaphrodite flowers), or trimonoecious (where each plant bears male, female and hermaphrodite flowers). Andromonecious and gynomonecious species are collectively monoeciously polygamous. Populations and species which are not synoecious are diclinous.

The term polygamous is applied generally to cases where there are 3 or more types of flower, or 3 or more types of plant, or to the condition where both unisexual and bisexual flowers are borne on a single plant. When a species is polyganous but mostly monoecious or dioecious it is termed polygamomonoecious or polygamodioecious respectively.

The prefix sub- is used form terms describing populations and species in which most, but not all plants, conform to one of the above. Only three forms are attested - a species in which most, but not all, plants bear only male or female flowers is subdioecious, one in which most, but not all, plants bear both male and female flowers is submonoecious.

References

  1. B. Daydon Jackson, A Glossary of Botanic Terms, 4th edn (1928)
  2. Vascular Plant Systematics

Malvaceous plants are generally synoecious, and this is presumably the plesiomorphic condition in Malvaceae, as in Magnoliophyta as a whole.

The largest subgroup departing from this condition is subfamily Sterculioideae (12 genera, 400 species) in which the flowers are usually functionally unisexual, or polygamous [1]. Sterculia may be monoecious or dioecious; Cola is usually dioecious [5]. Pterygota and Hildegardia are dioecious [3].

Grewioideae displays a tendency towards dioecism; here the genera Eleutherostylis, Hydrogaster, Tetralix and Vasivaea are dioecious, as are most species of Trichospermum, and some species of Grewia [1, 2]; and some species of Triumfetta are gynodioecious [1]. Heliocarpus is gynomonoecious, and Erinocarpus andromonoecious [1]. Some species of Carpodiptera and Christiana possess unisexual flowers [6].

In Byttnerioideae some species of Ayenia (Byttnerieae) and Dicarpidium (Hermannieae) possess unisexual flowers [1].

In Brownlowioidea Christiana may be monoecious (C. eburnea) or dioecious and Carpodiptera is dioecious [1, 2].

In Dombeyoidae some Mascarene species of Dombeya are dioecious, as are Astiria rosea and Ruizia cordata [3], and the flowers of Burretiodendron are functionally unisexual.

In Helecteroideae Mansonia and Triplochiton possess mostly, but not exclusively, hermaphrodite flowers [1].

In Malvoideae Kydia (Hibisceae) is subdioecious [2], and Hampea (Gossypieae) (excluding H. rosavirae) [8], Cienfuegosia heteroclada [9] and Napaea (Malveae) are dioecious [1]. The Plagianthus alliance, mostly, but not universally, departs from the hermaphrodite condition; Plagianthus is subdioecious (female and hermaphrodite flowers sometimes found on otherwise male plants) [7], Asterotrichion is monoecious or dioecious, Gynatrix mostly dioecious, and Lawrencia may be dioecious, polygamodioecious or hermaphrodite, but Hoheria is hermaphrodite [1, 2]. Gynodioecious species are found in Cienfuegosia (C. rosei) (Gossypieae) [8], Eremalche (E. kernensis), Sidalcea (S. hendersonii and S. malachroides [4]) and Callirhoe (all Malveae). Eremalche parryi and some other species of Sidalcea are polygamodioecious [4]. Kosteletzkya virginica is gynomonoecious-gynodioecious.

References

  1. Kubitzki & Bayer, Malvaceae, in Kubitzki, K. and Bayer, C., The Families and Genera of Vascular Plants Vol. 5: Malvales, Capparales and Non-betalain Caryophyllales (2003)
  2. Hutchinson, The genera of flowering plants. 2: 536-567 (1967)
  3. Humeau et al, Cryptic Dioecy and Leaky Dioecy in Endemic Species of Dombeya (Sterculiaceae) on La Réunion, American Journal of Botany 86(10): 14371447 (1999)
  4. Wiggins, Malvaceae, in Abrams, Ill. Fl. Pacific States 3 (1951)
  5. H. Wild, Sterculiaceae, in Exell & Meeuse, Flora Zambesiaca 1: 517 (1961)
  6. H. Wild, Tiliaceae, in Exell & Meeuse, Flora Zambesiaca 2: 33 (1961)
  7. Cheeseman, Manual of the New Zealand Flora, 2nd. edn. (1925)
  8. Fryxell, The Natural History of the Cotton Tribe (1979)
  9. Fryxell, The Genus Cienfuegosia Cav. (Malvaceae), Ann. Mo. Bot. Gard. 56(2): 179-250 (1969)

© 2005, 2007 Stewart R. Hinsley