AskDefine | Define bract

Dictionary Definition

bract n : a modified leaf or leaflike part just below and protecting an inflorescence

User Contributed Dictionary

English

Noun

  1. A leaf or leaf-like structure from the axil of which a flower stalk arises.

Extensive Definition

In botany, a bract is a modified or specialized leaf. Bracts are ordinarily associated with reproductive structures (subtending flowers, inflorescence axes, or cone scales). They are ordinarily reduced in size relative to foliage leaves, or of a different color or texture from foliage leaves, or both.
Some bracts are brightly colored and serve the function of attracting pollinators, either in concert with or instead of the perianth. An excellent example of this latter type of bract occurs in the Poinsettia plant (Euphorbia pulcherrima).
A small bract is called bracteole or bractlet. Technically it is any bract that arises on a pedicel instead of subtending it. In grasses, the bracts that enclose the florets are termed glumes.
Bracts that appear in a whorl subtending an inflorescence are collectively called an involucre. An involucre is a common feature under the inflorescences of many Apiaceae, Asteraceae, and Polygonaceae. Each flower in an inflorescence may have its own whorl of bracts, in this case called an involucel. Many asteraceous plants have bracts both at the flower base and inflorescence base. Those at the flower base — chaff (paleae or receptacular bracts) — are usually minute scales or bristles. Those at the base of the inflorescence or head — the involucral bracts (phyllaries) — are often green, narrow, and leafy.
A prophyll is a leaf-like structure, such as a bracteole, subtending a single flower or pedicel. The term can also mean the lower bract on a peduncle.
A spathe is a large bract that forms a sheath to enclose the flower cluster of certain plants such as palms and arums. In many arums, the spathe is petal-like, attracting pollinators to the flowers arranged on a type of spike called a spadix.
The frequently showy pair of bracts of cyathia of Euphorbia species in subgenus Lacanthis is termed cyathophylls.
Bracts subtend the cone scales in the seed cones of many conifers, and in some cases, such as Pseudotsuga, extend beyond the cone scales even in mature cones.

Gallery

Bougainvillea each cluster of three flowers is surrounded by three or six more colorful bracts
bract in German: Hochblatt
bract in German: Tragblatt
bract in Spanish: Bráctea
bract in Esperanto: Brakteo
bract in French: Bractée
bract in Indonesian: Daun pelindung
bract in Italian: Brattea
bract in Dutch: Schutblad (plant)
bract in Polish: podsadka
bract in Portuguese: Bráctea
bract in Turkish: Brahte

Synonyms, Antonyms and Related Words

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