The column, or technically the gynostemium, is a reproductive structure that can be found in several plant families:
Aristolochiaceae
The Aristolochiaceae () are a family, the birthwort family, of flowering plants with seven genera and about 400 known species belonging to the order Piperales. The type genus is '' Aristolochia'' L.
Description
They are mostly perennial, her ...
,
Orchidaceae
Orchids are plants that belong to the family (biology), family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan distribution, cosmopolitan plants that ...
, and
Stylidiaceae
The family Stylidiaceae is a taxon of dicotyledonous flowering plants. It consists of five genera with over 240 species, most of which are endemic to Australia and New Zealand. Members of Stylidiaceae are typically grass-like herbs or small shrub ...
.
It is derived from the fusion of both male and female parts (
stamen
The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10
Morphology and terminology
A stamen typically consists of a stalk called the filament ...
s and
pistil
Gynoecium (; ; : gynoecia) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl (botany), whorl of a flower; it consists ...
) into a single organ.
The top part of the column is formed by the anther, which is covered by an anther cap. This means that the ''style'' and ''stigma'' of the pistil, with the filaments and one or more anthers, are all united.
Orchidaceae
The stigma sits at the apex of the column in the front but is pointing downwards after
resupination
Resupination is derived from the Latin word ''resupinus'', meaning "bent back
with the face upward" or "on the back". " Resupination" is the noun form of the adjective "resupine" which means "being upside-down, supine or facing upward".
The word ...
(the rotation by 180 degrees before unfolding of the flower).
This stigma has the form of a small bowl, the clinandrium, a viscous surface embedding the (generally) single anther. On top of it all is the anther cap. Sometimes there is a small extension or little beak to the median stigma lobe, called
rostellum
The rostellum is a projecting part of the column in Orchidaceae flowers, and separates the male androecium from the female gynoecium, commonly preventing self-fertilisation. In many orchids, such as '' Orchis mascula'', the pollinia or pollen m ...
.
Column wings may project laterally from the stigma. The column foot is formed by the attachment of the
lip
The lips are a horizontal pair of soft appendages attached to the jaws and are the most visible part of the mouth of many animals, including humans. Mammal lips are soft, movable and serve to facilitate the ingestion of food (e.g. sucklin ...
to the basal protruding part of the column. One speaks of a mentum (chin) if the lateral
sepal
A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106
Etymology
The term ''sepalum'' ...
s are also basally adnate (which are attached to the foot of the column).
The column both releases
pollen
Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...
and also receives it (from another individual) for fertilization. In the family Orchidaceae, unlike almost all other
flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...
s, the single male anther at the tip of the ''column'' produces
pollen
Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...
that is not free and powdery but held in waxy masses of two, four or six pellets called ''
pollinia
A pollinium (: pollinia) is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as orchids and many species of milkwee ...
''. The transfer of ''pollinia'' from one flower to another, though highly efficient, is often reliant upon one particular species of
arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
s and it can be catastrophic for the population if its pollinator disappears from the community.
References
{{botany
Plant morphology
Pollination
Orchid morphology