|
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 often (but not always) 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 and/or sepals. The state of having bracts is referred to as bracteate, and conversely ebracteate, without bracts. Similarly bracteolate and ebracteolate. ==Variants== Some bracts are brightly colored and serve the function of attracting pollinators, either together with the perianth or instead of it. Examples of this type of bract include ''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. Image:Bougainvillea glabra.JPG|Bracts of ''Bougainvillea glabra'', differ in colour from the non-bract leaves, and attract pollinators Image:Banana bract.jpg|Bracts along a banana flower stalk surround the rows of flowers Image:E milii vulcanii ies.jpg|''Euphorbia milii'' var. ''vulcanii'' cyathia bearing a pair of pinkish cyathophylls Image:Ananas bracteatus var tricolor.jpg|Colourful bracts of ''Ananas bracteatus'' File:Bráctea Taraxacum officinale.jpg|Bracts, ''Taraxacum officinale'' File:IMG 1527Dogwood.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 with pink bracts surrounding small flower cluster 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「bract」の詳細全文を読む スポンサード リンク
|