Inflorescences & Its types

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In the name of GOD

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INFLORESCENCES & ITS TYPES

Professor:Dr.olanj

Provider:Miaad golriz

2015-1394

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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 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.

A flower that is not part of an inflorescence is called a solitary flower and its stalk is also referred to as a peduncle.

The fruiting stage of an inflorescence is known as an infructescence.

INFLORESCENCES :

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BRACTS :

Inflorescences usually have modified foliage different from the vegetative part of the plant.

any leaf associated with an inflorescence is called a bract.

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 it to 4 types.

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EBRACTEATE INFLORESCENCES:

No bracts in the inflorescence.

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BRACTEATE INFLORESCENCES:

The bracts in the inflorescence are very specialised , sometimes reduced to small scales, divided or dissected.

Pedicularis verticillata

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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.

Leafy-bracted inflorescences: Intermediate between bracteate and leafy inflorescence.

clematitis

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TERMINAL FLOWER:

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.

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INDETERMINATE INFLORESCENCE: Monopodial (racemose) growth. The terminal bud keeps growing and forming lateral flowers. A terminal flower is never formed.

DETERMINATE INFLORESCENCE: Sympodial (cymose) growth. The terminal bud forms a terminal flower and then dies out. Other flowers then grow from lateral buds.

Hint : Indeterminate and determinate inflorescences are sometimes referred to as open and closed inflorescences respectively.

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DETERMINATE INFLORESCENCE:

acropetal basipetal divergent

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INDETERMINATE INFLORESCENCE: 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)

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A raceme is an unbranched , indeterminate inflorescencewith pedicellate (having short floral stalks)

flowers along the axis.

Epilobium angustifolium

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A spike is a type of raceme with flowers that do nothave a pedicel.

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A racemose corymb is an unbranched, indeterminate inflorescence that is flat-topped or convex due to their outer pedicels

which are progressively longer than inner ones.

Ibris Umbellata

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An umbel is a type of raceme with a short axis and multiple floral pedicels of equal length that appear to arise from a common point.

Astrantia minor

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A spadix is a spike of flowers densely arranged around it, enclosed or accompanied by a highly specialised bract called a spathe. It is

characteristic of the Araceae family.

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A flower head or capitulum is a very contracted raceme in which the single sessile flowers share are borne on an enlarged stem.

It is characteristic of Dipsacaceae.

Dipsacus fullonum

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A catkin or ament is a scaly, generally drooping spike or raceme. Cymose or other complex inflorescences that are

superficially similar are also generally called thus.

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REFERENCES[1] Kubitzki, Klaus, and Clemens Bayer. 2002. Floweringplants, Dicotyledons: Malvales, Capparales, and nonbetalainCaryophyllales. The Families and genera of vascularplants, 5. Berlin: Springer. p. 77[2] Oxford English Dictionary. Raceme 2. Bot. A type ofinflorescence in which the flowers are arranged on short,nearly equal, lateral pedicels, at equal distances along asingle elongated axis[3] Collins English Dictionary. 8th Edition first published in2006[4] Oxford English Dictionary. Cyme(1) Bot. A species ofinflorescence wherein the primary axis bears a single terminalflower which develops first, the system being continuedby axes of secondary and higher orders which developsuccessively in like manner; a centrifugal or definiteinflorescence: opposed to Raceme. Applied esp. to compoundinflorescences of this type forming a more or lessflat head.

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