In botany, a bract is a modified or specialized leaf, associated with a reproductive structure such as a flower, inflorescence axis or cone scale.
Bracts are usually different from foliage leaves in size, color, shape or texture. They also look different from the parts of the flower, such as the petals or sepals.
A plant having bracts is referred to as bracteate
Variants
Some bracts are brightly coloured which aid in the attraction of pollinators, either together with the
perianth or instead of it. Examples of this type of bract include those of
Euphorbia pulcherrima (poinsettia) and
Bougainvillea: both of these have large colourful bracts surrounding much smaller, less colourful flowers.
In Poaceae, each floret (flower) is enclosed in a pair of papery bracts, called the lemma (lower bract) and palea (upper bract), while each spikelet (group of florets) has a further pair of bracts at its base called glumes. These bracts form the chaff that is usually removed from cereal grain during threshing and winnowing.
Bats may detect acoustic signals from dish-shaped bracts such as those of Marcgravia evenia.
A prophyll is a leaf-like structure, such as a bracteole, subtending (extending under) a single flower or pedicel. The term can also mean the lower bract on a peduncle.
The frequently showy pair of bracts of Euphorbia species in subgenus Lacanthis are the cyathophylls.
Bracts subtend the cone scales in the seed cones of many , and in some cases, such as Pseudotsuga, they extend beyond the cone scales.
species.]]
flower stalk surround the rows of flowers]]
var. vulcanii cyathia bearing a pair of pinkish cyathophylls.]]
species
Cornus florida inflorescence showing four large white bracts and central flower cluster.]]
dogwood cultivar with pink bracts surrounding small flower cluster.]] protected by two bracts before flower bloom.]]
Bracteole
A small bract is called a
bracteole or
bractlet. Technically this is any bract that arises
on a pedicel instead of subtending it.
Involucral bracts
Bracts that appear in a whorl subtending an
inflorescence are collectively called an
involucre. An involucre is a common feature beneath the inflorescences of many families, including the
Apiaceae (carrot family),
Asteraceae (sunflower or the daisy family),
Dipsacaceae, and
Polygonaceae. Each flower in an inflorescence may have its own whorl of bracts, in this case called an
involucel.They can be called
chaff,
paleas or
receptacular bracts and are usually minute scales or bristles. Many
Asteraceae plants have bracts at the base of each inflorescence.
The term involucre is also used for a highly conspicuous bract or bract pair at the base of an inflorescence. In the family Betulaceae, notably in the genera hornbeam and hazel, the involucre is a leafy structure that protects the developing nuts. Beggar-tick ( Bidens comosa) has narrow involucral bracts surrounding each inflorescence, each of which also has a single bract below it. There is then a pair of leafy bracts on the main stem and below those a pair of leaves.
Epicalyx
An epicalyx( forms an additional whorl around the calyx of a single flower) is a modification of bracteoles.
In other words, the epicalyx is a
group of bracts resembling a calyx or
bracteoles forming a whorl outer to the calyx.
It is a calyx-like extra whorl of floral appendages. Each individual segment of the epicalyx is called an
episepal because they resemble the sepals in them.
They are present in the hibiscus family,
Malvaceae.
Fragaria (strawberries) may or may not have an epicalyx.
Spathe
A
spathe is a large bract or a pair of bracts that forms a sheath to enclose the flower cluster of plants such as
Arecaceae,
, irises,
[Richard Lynch ] [Alex Casha ] and
(
Commelina).
Zephyranthes tubispatha in the
Amaryllidaceae derives its specific name from its tubular spathe. In many arums (family
Araceae), the spathe is petal-like, attracting pollinators to the flowers arranged on a type of spike called a spadix.
See also
