An inflorescence is a group or cluster of flowers A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to mediate the union of male sperm with female ovum in order to produce seeds. The process begins with pollination, is followed by fertilization, leading to the formation and dispersal of the seeds. For arranged on a stem A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , cones or other stems etc. The internodes distance one node from another. The term shoots is often confused with stems; shoots generally refer to new fresh that is composed of a main branch A branch or tree branch (sometimes referred to in botany as a ramus) is a woody structural member connected to but not part of the central trunk of a tree (or sometimes a shrub). Large branches are known as boughs and small branches are known as twigs or a complicated arrangement of branches. Strictly, it is the part of the shoot Shoots are new plant growth, they can include stems, flowering stems with flower buds, leaves. The new growth from seed germination that grows upward is a shoot where leaves will develop. In the spring, perennial plant shoots are the new growth that grows from the ground in herbaceous plants or the new stem and/or flower growth that grows on woody of seed plants The spermatophytes (also known as phanerogams) comprise those plants that produce seeds. They are a subset of the embryophytes or land plants. The living spermatophytes form five groups: where flowers A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to mediate the union of male sperm with female ovum in order to produce seeds. The process begins with pollination, is followed by fertilization, leading to the formation and dispersal of the seeds. For are formed and which is accordingly modified. The modifications can involve the length and the nature of the internodes A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , cones or other stems etc. The internodes distance one node from another. The term shoots is often confused with stems; shoots generally refer to new fresh and the phyllotaxis In botany, phyllotaxis or phyllotaxy is the arrangement of leaves on a plant stem, as well as variations in the proportions, compressions, swellings, adnations, connations and reduction of main and secondary axes.
The stem holding the whole inflorescence is called a peduncle In botany, a peduncle is a stalk supporting an inflorescence, or after fecundation a fruit and the main stem holding the flowers or more branches within the inflorescence is called the rachis In vertebrates a rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually form the supporting axis of the body and is then called the spine or vertebral column. Rachis can also mean the central shaft of pennaceous feathers. The stalk of each single flower is called a pedicel A pedicel is a stem that attaches single flowers to the main stem of the inflorescence. It is the branches or stalks that hold each flower in an inflorescence that contains more than one flower.
The fruiting The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state, such as apples, oranges, grapes, strawberries, juniper berries and bananas. Seed-associated structures that do not fit these stage of an inflorescence is known as an infructescence.
A flower that is not part of an inflorescence is called a solitary flower and its stalk is also referred to as a peduncle.
Contents |
General characteristics
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.
Bracts
Inflorescences usually have modified 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 In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves, for example being smaller, larger, or of a different color or texture. 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:
- Ebracteate inflorescences: No bracts in the inflorescence.
- Bracteate inflorescences: The bracts in the inflorescence are very specialised, sometimes reduced to small scales, divided or dissected.
- Leafy inflorescences: Though often reduced in size, the bracts are unspecialised and look like the typical leaves of the plant, so that the term flowering stem is usually applied instead of inflorescence. This use is not technically correct, as, despite their 'normal' appearance, these leaves are considered, in fact, bracts, so that 'leafy inflorescence' is preferable.
- Leafy-bracted inflorescences: Intermediate between bracteate and leafy inflorescence.
If many bracts are present and they are strictly connected to the stem, like in the family Asteraceae The Asteraceae or Compositae, also referred to as the aster, daisy, or sunflower family, is the largest family of vascular plants. The family has more than 22,750 currently accepted species, spread across 1620 genera, and 12 subfamilies. The largest genera are Senecio , Vernonia (1,000 species), Cousinia (600 species) and Centaurea (600 species), 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. |
Terminal flower
Plant organs can grow according to two different schemes, namely monopodial and sympodial. In inflorescences these two different growth patterns are called indeterminate or determinate, and indicate whether a terminal flower is formed and where flowering starts within the inflorescence.
- Indeterminate inflorescence: Monopodial growth. The terminal bud keeps growing and forming lateral flowers. A terminal flower is never formed.
- Determinate inflorescence: Sympodial growth. The terminal bud forms a terminal flower and then dies out. Other flowers then grow from lateral buds.
Indeterminate and determinate inflorescences are sometimes referred to as open and closed inflorescences respectively.
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 |
In 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 a acropetal maturation and lateral flower buds. |
Indeterminate inflorescence with the subterminal flower to simulate the terminal one (vestige present) |
Phyllotaxis
As with leaves In botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. As an evolutionary trait, the flatness of leaves works to expose the chloroplasts to more light and to increase the absorption of carbon dioxide at the expense of water loss. In the Devonian period, when carbon, flowers can be arranged on the stem according to many different patterns. See 'Phyllotaxis In botany, phyllotaxis or phyllotaxy is the arrangement of leaves on a plant stem' for in-depth descriptions.
|
Alternate flowers |
Opposite flowers |
Metatopy
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:
- Some plants have bracts that subtend the inflorescence, where the flowers are on branched stalks; the bracts are not connected to the stalks holding the flowers, but are adnate or attached to the main stem (Adnate describes the fusing together of different unrelated parts. When the parts fused together are the same, they are connately joined)
- Other plants have the bracts subtend the pedicel or peduncle of single flowers.
Metatopic placement of bracts include:
- When the bract is attached to the stem holding the flower (the pedicel or peduncle), it is said to be recaulescent; sometimes these bracts or bracteoles are highly modified and appear to be appendages of the flower calyx. Recaulescences is the fusion of the subtending leaf with the stem holding the bud or the bud itself,[1] thus the leaf or bract is adnate to the stem of flower.
- When the formation of the bud is shifted up the stem distinctly above the subtending leaf, it is described as concaulescent.
|
Flower and subtending bract |
Lilium martagon (flower and subtending bract) |
Concaulescence |
|
|
Recaulescence |
Organization
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.
Inflorescences can be simple or compound.
Statesman Journal
The leafless stems are topped by a rather impressive inflorescence . This flower cluster is especially impressive this time of year when illuminated by the ...
