出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/21 04:28:04」(JST)
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified. The modifications can involve the length and the nature of the internodes and the phyllotaxis, as well as variations in the proportions, compressions, swellings, adnations, connations and reduction of main and secondary axes. Inflorescence can also be defined as the reproductive portion of a plant that bears a cluster of flowers in a specific pattern.
The stem holding the whole inflorescence is called a peduncle and the major axis (incorrectly referred to as the main stem) holding the flowers or more branches within the inflorescence is called the rachis. The stalk of each single flower is called a pedicel. A flower that is not part of an inflorescence is called a solitary flower and its stalk is also referred to as a peduncle. Any flower in an inflorescence may be referred to as a floret, especially when the individual flowers are particularly small and borne in a tight cluster, such as in a pseudanthium. The fruiting stage of an inflorescence is known as an infructescence.
Inflorescences may be simple (single) or complex (panicle). The rachis may be one of several types, including Single, Composite, Umbel, Spike or Raceme.
Inflorescences are described by many different characteristics including how the flowers are arranged on the peduncle, the blooming order of the flowers and how different clusters of flowers are grouped within it. These terms are general representations as plants in nature can have a combination of types.
Inflorescences usually have modified shoots foliage different from the vegetative part of the plant. Considering the broadest meaning of the term, any leaf associated with an inflorescence is called a bract. A bract is usually located at the node where the main stem of the inflorescence forms, joined to the main stem of the plant, but other bracts can exist within the inflorescence itself. They serve a variety of functions which include attracting pollinators and protecting young flowers. According to the presence or absence of bracts and their characteristics we can distinguish:
If many bracts are present and they are strictly connected to the stem, like in the family Asteraceae, the bracts might collectively be called an involucre. If the inflorescence has a second unit of bracts further up the stem, they might be called an involucel.
Ebracteate inflorescence.
Ebracteate of Wisteria sinensis
Bracteate inflorescence.
Bracteate inflorescence of Pedicularis verticillata.
Leafy-bracted inflorescence.
Leafy-bracted inflorescence of Rhinanthus angustifolius.
Leafy inflorescence.
Leafy inflorescence of Aristolochia clematitis.
Plant organs can grow according to two different schemes, namely monopodial or racemose and sympodial or cymose. In inflorescences these two different growth patterns are called indeterminate and determinate respectively, and indicate whether a terminal flower is formed and where flowering starts within the inflorescence.
Indeterminate and determinate inflorescences are sometimes referred to as open and closed inflorescences respectively.
In an indeterminate inflorescence there is no true terminal flower and the stem usually has a rudimentary end. In many cases the last true flower formed by the terminal bud (subterminal flower) straightens up, appearing to be a terminal flower. Often a vestige of the terminal bud may be noticed higher on the stem.
Indeterminate inflorescence with a perfect acropetal maturation.
Indeterminate inflorescence with an acropetal maturation and lateral flower buds.
Indeterminate inflorescence with the subterminal flower to simulate the terminal one (vestige present)
In determinate inflorescences the terminal flower is usually the first to mature (precursive development), while the others tend to mature starting from the bottom of the stem. This pattern is called acropetal maturation. When flowers start to mature from the top of the stem, maturation is basipetal, while when the central mature first, divergent.
Determinate inflorescence with acropetal maturation
Determinate inflorescence with basipetal maturation
Determinate inflorescence with divergent maturation
As with leaves, flowers can be arranged on the stem according to many different patterns. See 'Phyllotaxis' for in-depth descriptions.
Alternate flowers
Opposite flowers
Metatopy is the placement of organs out of their normally expected position: typically metatopy occurs in inflorescences when unequal growth rates alter different areas of the axis and the organs attached to the axis.
When a single or a cluster of flower(s) is located at the axil of a bract, the location of the bract in relation to the stem holding the flower(s) is indicated by the use of different terms and may be a useful diagnostic indicator.
Typical placement of bracts include:
Metatopic placement of bracts include:
Flower and subtending bract
Lilium martagon (flower and subtending bract)
Concaulescence
Solanum lycopersicum (concaulescence)
Recaulescence
Tilia cordata (recaulescence)
There is no general consensus in defining the different inflorescences. The following is based on Focko Weberling's Morphologie der Blüten und der Blütenstände (Stuttgart, 1981). The main groups of inflorescences are distinguished by branching. Within these groups, the most important characteristics are the intersection of the axes and different variations of the model. They may contain many flowers (pluriflor) or a few (pauciflor). Inflorescences can be simple or compound.
Indeterminate simple inflorescences are generally called racemose /ˈræsɨmoʊs/. The main kind of racemose inflorescence is the raceme (/ˈræsiːm/, from classical Latin racemus, cluster of grapes).[2] The other kind of racemose inflorescences can all be derived from this one by dilation, compression, swelling or reduction of the different axes. Some passage forms between the obvious ones are commonly admitted.
Raceme
Epilobium angustifolium
Spike
Plantago media (spike)
Racemose corymb
Iberis umbellata (racemose corymb)
Umbel
Astrantia minor (umbel)
Spadix
Arum maculatum (spadix)
Head (round)
Dipsacus fullonum (head)
Catkin (racemose or spicate)
Alnus incana (ament)
Determinate simple inflorescences are generally called cymose. The main kind of cymose inflorescence is the cyme (pronounced 'saim', from the Latin cyma in the sense ‘cabbage sprout’, from Greek kuma ‘anything swollen’[3]).[4] Cymes are further divided according to this scheme:
Double cyme
Double cyme
Bostryx (lateral and top view)
Hypericum perforatum (bostryx)
Drepanium (lateral and top view)
Gladiolus imbricatus (drepanium)
Cincinnus (lateral and top view)
Symphytum officinale (cincinnus)
Rhipidium (lateral and top view)
Canna sp. (rhipidium)
Dichasium
Dichasium, top view
Silene dioica (dichasium)
A cyme can also be so compressed that it looks like an umbel. Strictly speaking this kind of inflorescence could be called umbelliform cyme, although it is normally called simply 'umbel'.
Another kind of definite simple inflorescence is the raceme-like cyme or botryoid; that is as a raceme with a terminal flower and is usually improperly called 'raceme'.
Umbelliform cyme
Pelargonium zonale (umbelliform cyme)
Botryoid
Berberis vernae (botryoid)
A reduced raceme or cyme that grows in the axil of a bract is called a fascicle. A verticillaster is a fascicle with the structure of a dichasium; it is common among the Lamiaceae. Many verticillasters with reduced bracts can form a spicate (spike-like) inflorescence that is commonly called a spike.
Gentiana lutea (fascicles)
Lamium orvala (verticillaster)
Mentha longifolia ('spike')
Simple inflorescences are the basis for compound inflorescences or synflorescences. The single flowers are there replaced by a simple inflorescence, which can be both a racemose or a cymose one. Compound inflorescences are composed of branched stems and can involve complicated arrangements that are difficult to trace back to the main branch.
A kind of compound inflorescence is the double inflorescence, in which the basic structure is repeated in the place of single florets. For example a double raceme is a raceme in which the single flowers are replaced by other simple racemes; the same structure can be repeated to form triple or more complex structures.
Compound raceme inflorescences can either end with a final raceme (homoeothetic), or not (heterothetic). A compound raceme is often called a panicle. Note that this definition is very different from that given by Weberling.
Compound umbels are umbels in which the single flowers are replaced by many smaller umbels called umbellets. The stem attaching the side umbellets to the main stem is called a ray.
Homeothetic compound raceme
Melilotus officinalis (homoeothetic compound raceme)
Heterothetic compound raceme
Hebe albicans (heterothetic compound raceme)
Compound spike
Lolium temulentum (compound spike)
Compound capitulum
Echinops ritro (compound capitulum)
Compound (double) umbel
Laserpicium latifolium (double umbel)
Compound (triple) umbel
The most common kind of definite compound inflorescence is the panicle (of Webeling, or 'panicle-like cyme'). A panicle is a definite inflorescence that is increasingly more strongly and irregularly branched from the top to the bottom and where each branching has a terminal flower.
The so-called cymose corymb is similar to a racemose corymb but has a panicle-like structure. Another type of panicle is the anthela. An anthela is a cymose corymb with the lateral flowers higher than the central ones.
Panicle
Vitis vinifera (panicle)
Cymose corymb
Sambucus nigra (cymose corymb)
Anthela
Juncus inflexus (anthela)
A raceme in which the single flowers are replaced by cymes is called a (indefinite) thyrse. The secondary cymes can of course be of any of the different types of dichasia and monochasia. A botryoid in which the single flowers are replaced by cymes is a definite thyrse or thyrsoid. Thyrses are often confusingly called panicles.
Thyrse
Aesculus hippocastanum
Thyrsoid
Syringa vulgaris
Other combinations are, of course, possible. For example, heads or umbels may be arranged in a corymb or a panicle.
Achillea sp. (heads in a corymb)
Hedera helix (umbels in a panicle)
The family Asteraceae is characterised by a highly specialised head technically called a calathid (but usually referred to as 'capitulum' or 'head'). The family Poaceae has a peculiar inflorescence of small spikes (spikelets) organised in panicles or spikes that are usually simply and improperly referred to as spike and panicle. The genus Ficus (Moraceae) has an inflorescence called syconium and the genus Euphorbia has cyathia (sing. cyathium), usually organised in umbels. For detailed descriptions, see the respective articles.
Matricaria chamomilla (calathid)
Triticum aestivum (compound spikes, "spikes")
Oryza sativa (spikes in a panicle, "panicle")
Ficus carica (syconium)
Euphorbia tridentata (cyathium)
Euphorbia cyparissias (cyathia in an umbel)
(Coleus-false spike)
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