Floral symmetry 709092 218051388 2008-06-08T22:56:51Z Vlmastra 3134438 '''Floral symmetry''' refers to whether, and how, a [[flower]] can be divided into two or more identical or mirror-image parts. Most flowers are '''actinomorphic''' ("star shaped"), meaning they can be divided into symmetrical halves by more than one longitudinal plane passing through the axis, much as a pie can be cut into several equal and identical pieces. In these flowers, the [[petal]]s are usually similar in shape, size, and color. Such flowers are also called [[symmetry (biology)#Radial symmetry|radially symmetrical]] or regular flowers. Examples of actinomorphic flowers are the [[lily]] (''[[Lilium]]'', [[Liliaceae]]) and the [[buttercup]] (''[[Ranunculus]]'', [[Ranunculaceae]]). '''Zygomorphic''' ("yoke shaped") flowers can be divided by only a single plane into two mirror-image halves, much like a [[yoke]] or a person's face. Examples are [[orchid]]s and the flowers of most members of the [[Lamiales]] (e.g., [[Scrophulariaceae]] and [[Gesneriaceae]]). Zygomorphic flowers generally have petals of two more different shapes, sizes, and colors. Least commonly, flowers may be asymmetrical; they cannot be divided into two identical or mirror-image halves on any plane. Such flowers are typical of most members of the [[Zingiberales]], such as [[Canna (plant)|cannas]] and various [[ginger]]s. In most cases, different kinds of floral symmetry are linked to particular pollinators. Actinomorphic flowers are a basal angiosperm character; zygomorphic flowers are a derived character that has evolved many times.<ref name=Bio8>Losos, J. B., Mason, K. A, & Singer, S. R. ''Biology, 8th. ed.'' New York, NY: McGraw Hill.</ref> Some familiar and seemingly actinomorphic flowers, such as those of [[daisies]] and [[dandelions]] ([[Asteraceae]]), are actually clusters of tiny zygomorphic flowers arranged into a radially symmetric [[inflorescence]]. '''Peloria''' or a '''peloric flower''' refers to an aberration in which a plant that normally produces zygomorphic flowers produces actinomorphic flowers instead. This aberration can be developmental, or it can have a genetic basis: the [[CYCLOIDEA]] gene controls floral symmetry. Peloric ''[[Antirrhinum]]'' plants have been produced by knocking out this gene.<ref name=Bio8/> Many modern cultivars of ''[[Sinningia speciosa]]'' ("gloxinia") have been bred to have peloric flowers as they are larger and showier than the normally zygomorphic flowers of this species. ==References== {{Reflist}} * P.K. Endress. 2001. Evolution of floral symmetry. ''Current Opinions in Plant Biology'' 4: 86-91 (abstract [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11163173&dopt=Citation here]) * P.R. Neal, A. Dafni and M. Giurfa. 1998. Floral symmetry and its role in plant-pollinator systems: terminology, distribution, and hypotheses. ''Annual Review of Ecology and Systematics'' 29: 345-373 (abstract [http://www.jstor.org/view/00664162/ap010001/01a00130/0 here]). [[Category:plant morphology]] {{botany-stub}} [[pt:Simetria floral]]