Inbotany, abract is a modified or specializedleaf, associated with a reproductive structure such as aflower,inflorescence axis orcone 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 orsepals.
A plant having bracts is referred to asbracteate[1] orbracteolate, while one that lacks them is referred to asebracteate[2] orebracteolate.
Some bracts are brightly coloured which aid in the attraction of pollinators, either together with theperianth or instead of it. Examples of this type of bract include those ofEuphorbia pulcherrima (poinsettia) andBougainvillea: both of these have large colourful bracts surrounding much smaller, less colourful flowers.[3]
Ingrasses, each floret (flower) is enclosed in a pair of papery bracts, called thelemma (lower bract) andpalea (upper bract), while each spikelet (group of florets) has a further pair of bracts at its base calledglumes. These bracts form thechaff that is usually removed fromcereal grain duringthreshing andwinnowing.[4]
Bats may detect acoustic signals from dish-shaped bracts such as those ofMarcgravia evenia.[5]
Aprophyll is a leaf-like structure, such as a bracteole, subtending (extending under) a single flower orpedicel. The term can also mean the lower bract on apeduncle.
The frequently showy pair of bracts ofEuphorbia species in subgenusLacanthis are thecyathophylls.
Bracts subtend the cone scales in the seed cones of manyconifers, and in some cases, such asPseudotsuga, extend beyond the cone scales.
A small bract is called abracteole orbractlet. Technically this is any bract that ariseson a pedicel instead of subtending it.
Bracts that appear in awhorl subtending aninflorescence are collectively called aninvolucre. An involucre is a common feature beneath the inflorescences of many families, including theApiaceae (carrot family),Asteraceae (sunflower or the daisy family),Dipsacaceae, andPolygonaceae. Each flower in an inflorescence may have its own whorl of bracts, in this case called aninvolucel. They can be calledchaff,paleas orreceptacular bracts and are usually minute scales or bristles. Manyasteraceous plants have bracts at the base of each inflorescence.[6]
The terminvolucre is also used for a highly conspicuous bract or bract pair at the base of an inflorescence. In the familyBetulaceae, notably in the generaCarpinus andCorylus, theinvolucre 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.[6]
An epicalyx (which forms an additional whorl around thecalyx of a single flower) is a modification of bracteoles.[7] In other words, the epicalyx is a group of bracts resembling a calyx or bracteoles forming a whorl outer to the calyx.[8][page needed] It is a calyx-like extra whorl of floral appendages. Each individual segment of the epicalyx is called anepisepal because they resemble the sepals in them.[9] They are present in the hibiscus family,Malvaceae.Fragaria (strawberries) may or may not have an epicalyx.
Aspathe is a large bract or a pair of bracts that forms a sheath to enclose the flower cluster of plants such aspalms,arums,irises,[10]crocuses[11] anddayflowers (Commelina).Zephyranthes tubispatha in theAmaryllidaceae derives itsspecific name from its tubular spathe. In many arums (familyAraceae), the spathe is petal-like, attracting pollinators to the flowers arranged on a type of spike called aspadix.
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