involucre

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 usually different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture. Typically, 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 or bracteolate, while one that lacks them is referred to as ebracteate and ebracteolate, without bracts.

Variants

Some bracts are brightly-coloured and serve the function of attracting 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 grasses, 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 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 conifers, and in some cases, such as ''Pseudotsuga'', they extend beyond the cone scales.

File:Castilleja levisecta bracts.jpg, Bright yellow bracts of ''Castilleja levisecta'' are more tightly pressed against the stem than bracts of other '' Castilleja'' species.
File:Bougainvillea glabra.JPG, Bracts of ''Bougainvillea glabra'', differ in colour from the non-bract leaves, and attract pollinators.
File:Banana bract.jpg, Bracts along a banana flower stalk surround the rows of flowers
File:E milii vulcanii ies.jpg, ''Euphorbia milii'' var. ''vulcanii'' cyathia bearing a pair of pinkish cyathophylls.
File:Ananas bracteatus var tricolor.jpg, Colourful bracts of ''Ananas bracteatus''.
File:Erigeron peregrinus 6287.JPG, The many green involucral bracts of ''Erigeron peregrinus'' are linear, loose, taper to a point, about the same length, and help to distinguish this species.
File:Blooming Dogwood.jpg, Dogwood species ''Cornus florida'' inflorescence showing four large white bracts and central flower cluster.
File:2013-05-10 08 26 08 Closeup of pink dogwoods at the Brendan T. Byrne State Forest headquarters.jpg, ''Cornus florida'' dogwood cultivar with pink bracts surrounding small flower cluster.
File:豔紅苞鳳梨 20190712192436.jpg, The red bracts of '' Aechmea bracteata''.
File:女王鬱金 20190715203108 01.jpg, The pink bracts of '' Curcuma petiolata''.
File:火鶴 20190729181532.jpg, The pink bract of a new cultivar: '' Anthurium andraeanum'' 'Pink Lady'.
File:豔山姜花序總苞 20190508131956.jpg, The inflorescence of '' Alpinia zerumbet'' protected by two bracts before flower bloom.
File:地湧金蓮 Musella lasiocarpa 20201028130818 01.jpg, The golden bracts of ''Musella lasiocarpa''.
File:Hydrangea involucrata (9344379310).jpg, Large bracts of '' Hydrangea involucrata'' surround tiny flowers and demonstrate the "lacecap" style inflorescence that has made various ''Hydrangea'' species and cultivars popular with gardeners.
File:Viburnum opulus RF.jpg, Like many ''Hydrangea'' species (Hydrangeaceae family), ''Viburnum opulus'' (Adoxaceae family) has bracts that surround tiny flowers, creating a "lacecap" style inflorescence.

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 Apiaceae, Asteraceae, Dipsacaceae and Polygonaceae. Each flower in an inflorescence may have its own whorl of bracts, in this case called an involucel. In this case they may be called ''chaff'', ''paleas'', or ''receptacular bracts'' and are usually minute scales or bristles. Many asteraceous 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 ''Carpinus'' and ''Corylus'', 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, which 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 pair of bracts forming a sheath to enclose the flower cluster of such plants as palms, arums, irises,Richard Lynch crocuses,Alex Casha and dayflowers ('' 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.

References

{{Botany

Plant morphology
Leaves