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Review
. 2005 Feb;17(2):330-41.
doi: 10.1105/tpc.104.030353.

Morphogenesis of flowers--our evolving view

David R Smyth  1
Affiliations
Review

Morphogenesis of flowers--our evolving view

David R Smyth. Plant Cell. 2005 Feb.
No abstract available

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Figures

Figure 1.
Figure 1.
The Basis of Linnaeus' Sexual System for the Classification of Flowering Plants. Linnaeus defined 24 classes based on the number of stamens per flower (A to N), their variable length (O to P), their degree of fusion (Q to U), and the presence of some flowers without stamens (V to Y) and of plants apparently without flowers (Z). He then subdivided classes into orders mostly based on the number of styles (carpels) in each flower. Each order was then again divided into genera based on six other floral and fruit characteristics. Finally, similar plants within a genus were given a single Latin descriptor, now know as the species name. The genus and species names are the binomial system we use today. (Watercolor by Georg Dionysius Ehret drawn in 1736. Original held in the Natural History Museum, London, UK, and reproduced with permission.)
Figure 2.
Figure 2.
Variations in Floral Structure. (A) The symmetry of flowers is defined by the number of similar axes that can be drawn through its plan. Radially symmetric flowers (also called regular or actinomorphic) have two or more axes and include many monocots (3), Arabidopsis (2, derived from 4), tomato, and Petunia (5). Bilaterally symmetric flowers (also called irregular, zygomorphic, or mirror-imaged) have only one and include Antirrhinum and the pea family (Papilionaceae). (B) Phyllotaxy of organs may be spiral (especially in the basal angiosperms) or whorled. (C) Organs may arise alternate with, or opposite to, those in the adjacent whorl. (D) Duplication of organs may occur by the reiteration of a whorl (as in poppies) or by two organs arising in place of one or vice versa (dédoublement, as in Lepidium [Brassicaceae]). (E) Organs may either be free or show different patterns of fusion with each other. Those within a whorl may be coherent in a tube (e.g., the corolla of Antirrhinum). Different types of organ may be adherent (e.g., the stamens and corolla of Antirrhinum). These forms are usually congenital. Post-genital fusions occur after organs have formed (e.g., anthers in the daisy family, Asteraceae). (F) The place of attachment of the perianth organs and stamens varies. They may be attached to the receptacle near the base of the ovary (hypogynous) or at the top of the ovary (epigynous). They are sometimes attached on the rim of a floral tube (perigynous), which itself may be basal or apical to the ovary. The ovary is either superior if the other organs (or a floral tube) are attached to its base or inferior if they are attached to its apex. The floral tube is sometimes called a hypanthium.
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References

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    1. Angiosperm Phylogeny Group (2003). An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. Bot. J. Linn. Soc. 141, 399–436.
    1. Arber, A. (1937). The interpretation of the flower: A study of some aspects of morphological thought. Biol. Rev. 12, 157–184.
    1. Arber, A. (1950). The Natural Philosophy of Plant Form. (Cambridge, UK: Cambridge University Press).
    1. Aukerman, M.L., and Sakai, H. (2003). Regulation of flowering time and floral organ identity by a microRNA and its APETALA2-like target genes. Plant Cell 15, 2730–2741. - PMC - PubMed

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