Journal Article

Evolution of petal epidermal micromorphology in Leguminosae and its use as a marker of petal identity

Isidro Ojeda, Javier Francisco-Ortega and Quentin C. B. Cronk

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 104, issue 6, pages 1099-1110
Published in print November 2009 | ISSN: 0305-7364
Published online September 2009 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcp211
Evolution of petal epidermal micromorphology in Leguminosae and its use as a marker of petal identity

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

The legume flower is highly variable in symmetry and differentiation of petal types. Most papilionoid flowers are zygomorphic with three types of petals: one dorsal, two lateral and two ventral petals. Mimosoids have radial flowers with reduced petals while caesalpinioids display a range from strongly zygomorphic to nearly radial symmetry. The aims are to characterize the petal micromorphology relative to flower morphology and evolution within the family and assess its use as a marker of petal identity (whether dorsal, lateral or ventral) as determined by the expression of developmental genes.

Methods

Petals were analysed using the scanning electron microscope and light microscope. A total of 175 species were studied representing 26 tribes and 89 genera in all three subfamilies of the Leguminosae.

Key Results

The papilionoids have the highest degree of variation of epidermal types along the dorsiventral axis within the flower. In Loteae and genistoids, in particular, it is common for each petal type to have a different major epidermal micromorphology. Papillose conical cells are mainly found on dorsal and lateral petals. Tabular rugose cells are mainly found on lateral petals and tabular flat cells are found only in ventral petals. Caesalpinioids lack strong micromorphological variation along this axis and usually have only a single major epidermal type within a flower, although the type maybe either tabular rugose cells, papillose conical cells or papillose knobby rugose cells, depending on the species.

Conclusions

Strong micromorphological variation between different petals in the flower is exclusive to the subfamily Papilionoideae. Both major and minor epidermal types can be used as micromorphological markers of petal identity, at least in papilionoids, and they are important characters of flower evolution in the whole family. The molecular developmental pathway between specific epidermal micromorphology and the expression of petal identity genes has yet to be established.

Keywords: Epidermis; Fabaceae; Papilionoideae; Caesalpinioideae; Mimosoideae; petal surface; scanning electron microscopy; papillose conical cells; tabular rugose cells; tabular flat cells; organ identity

Journal Article.  7188 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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