Monocracy
Monözie ( ancient Greek μόνος mónos "alone", "only" and οἰκία oikia "house") or monoeye , is the presence of female (carpenter, pistillate) and male (staminate) flowers on a plant specimen in seed plants. The flowers are unisexual, so either have only (male) stamens or only (female) carpels . The sexual organs of the plant are spatially separated ( diclinic ). The whole plant is hermaphroditic .
In the case of gametophytes , monözie denotes that male and female sexual organs occur, in the case of algae and fungi on a clone .
The opposite of monocyte is diocyte , the mixed form is the subdiocyte .
Seed plants
Monocular seed plants produce unisexual flowers on a plant. However, they can change their gender relatively easily. This happens through genetic modification of their male-sterile genes or the female-sterile genes, or through environmental influences.
Monoecism is considered to be a derived feature, the original angiosperms blossoms were hermaphrodite. The development to monoecia should proceed via andromonoce (male and hermaphrodite flowers) and gyno monocee (female and hermaphrodite flowers). These two forms of sex distribution are found relatively frequently in species with umbrella-shaped or head-shaped inflorescences .
Mostly male and female flowers are arranged on the plant according to a certain scheme. In most sedges ( Carex ) the female flowers or spikelets are below (proximal) and the male above (distal).
Most species with monoecia are wind or water pollinated ( anemophilia or hydrophilicity ). Monocyte is a more efficient system for cross-pollinators than hermaphrodite flowers. In many monocial trees, young plants produce predominantly or exclusively male flowers, while older plants predominantly produce female flowers. This is explained by the fact that large trees have greater resources and are therefore better able to produce the resource-intensive seeds and fruits. For the same reason, plants under stress are likely to produce predominantly male flowers. The ratio of male to female flowers should be controlled by the ratio of cytokinin to auxin . Some epiphytic orchids such as Catasetum viridiflavum also form male flowers as small plants, later female flowers.
In many cases, the monocy was probably the starting point for the evolution of the diocese . In the case of cultivated plants , however, in some cases monoecious varieties were bred from the originally dioecious species, for example the grapevine Vitis vinifera and the hemp ( Cannabis sativa ). This avoids the economic disadvantage of having to plant unproductive male plants.
literature
- Adrian J. Richards: Plant Breeding Systems. 2nd ed. Chapman & Hall, London 1997, ISBN 0-412-57440-3 , pp. 337-341.
- Andreas Bresinsky , Christian Körner , Joachim W. Kadereit , Gunther Neuhaus , Uwe Sonnewald : Textbook of botany . Founded by Eduard Strasburger . 36th edition. Spektrum Akademischer Verlag, Heidelberg 2008, ISBN 978-3-8274-1455-7 , p. 802 .
Individual evidence
- ^ Gerhard Wagenitz : Dictionary of Botany. The terms in their historical context. 2nd, expanded edition. Spektrum Akademischer Verlag, Heidelberg / Berlin 2003, ISBN 3-8274-1398-2 , p. 204.