Petals are often the most obvious organ within a flower because they provide visually arresting targets for varied pollinators and show corresponding adaptions in form, colour and scent. When present, they are located in the outer layers of a flower (the perianth) surrounding the male and female reproductive organs, the stamens and carpels. Their development is a consequence of a regulatory hierarchy of meristem determining genes, organ identity genes and downstream target genes. The gene hierarchy involves transcription factors from varied families and is regulated at transcriptional and posttranscriptional levels, involving microRNAs (ribonucleic acids) and targeted protein degradation. The nature of the gene and protein interactions determining and controlling many aspects of petal development have been teased apart in dicotyledonous flowers of Arabidopsis, Antirrhinum and Petunia and in recent years, this knowledge has been used to explore the evolution of these developmental genetic systems across the angiosperms.

Key concepts:

  • Molecular genetics has identified key regulators of petal development in model species.

  • Petal initiation and subsequent development is regulated by a range of transcription factor types.

  • Petal characteristics such as colour, shape and scent are related to pollination mechanisms.

  • Ethylene is important in petal senescence.

Keywords: flower; whorls; pollination; evolution; regulatory genes; developmental genetics

Figure 1.

Variation in petal and floral structure and arrangement. (a) Typical petal consisting of blade, B, and claw, C, regions as found in Arabidopsis thaliana. (b) Zygomorphic flower from Antirrhinum majus observed in dorsoventral view, showing the dorsal, D, lateral, L and ventral, V, petals. (c) Rice flower showing the presence of lodicules, Lo, in a position corresponding to petals in other flowers.

Figure 2.

The development and specification of petals. (a) Floral meristem showing sepal primordia, Se, and the position where the petals, P, stamens, St, and carpel, C, will emerge. (b) Flower at later stage of development showing the developing organs in all whorls. (c) Mature flower and a schematic of how the combinatorial activities of the A, B and E genes specify petal identity. A and E factors are represented by green and grey circles and B‐class factors by red and yellow circles.

Figure 3.

Specialized cells of the petal epidermis. (a) Conical cells in the petal epidermis (viewed here in a scheme of a petal transverse section) enhance the colour of flowers by increasing the amount of incidental light (indicated by arrows) absorbed by the cells and reducing the amount of white light that is reflected by the cells. At a visual level, this translates into a more vibrant colour in the petals. The conical cells also provide a more attractive landing platform for pollinators. (b) Flat epidermal cells will make the petal appear paler.

Figure 4.

The evolution of petals. (a) Scheme summarizing the pattern of AP3/PI duplication in the angiosperms. Arrows indicate gene duplication events. (b) Silencing of both AP3 duplicates in opium poppy results in homeotic conversion of petals and stamens (on the left). Reproduced with permission from Drea et al. .



Almeida J, Rocheta M and Galego L (1997) Genetic control of flower shape in Antirrhinum majus. Development 124: 1387–1392.

Baker CC, Sieber P, Wellmer F and Meyerowitz EM (2005) The early extra petals1 mutant uncovers a role for microRNA miR164c in regulating petal number in Arabidopsis. Current Biology 15: 303–315.

Baumann K, Perez‐Rodriguez M, Bradley D et al. (2007) Control of cell and petal morphogenesis by R2R3 MYB transcription factors. Development 134: 1691–1701.

Bey M, Stuber K, Fellenberg K et al. (2004) Characterization of Antirrhinum petal development and identification of target genes of the class B MADS box gene DEFICIENS. Plant Cell 16: 3197–3215.

Brewer PB, Howles PA, Dorian K et al. (2004) PETAL LOSS, a trihelix transcription factor gene, regulates perianth architecture in the Arabidopsis flower. Development 131: 4035–4045.

Broholm SK, Tahtiharju S, Laitinen RA et al. (2008) A TCP domain transcription factor controls flower type specification along the radial axis of the Gerbera (Asteraceae) inflorescence. Proceedings of the National Academy of Sciences of the USA 105: 9117–9122.

Busch A and Zachgo S (2007) Control of corolla monosymmetry in the Brassicaceae Iberis amara. Proceedings of the National Academy of Sciences of the USA 104: 16714–16719.

Chae E, Tan QK, Hill TA and Irish VF (2008) An Arabidopsis F‐box protein acts as a transcriptional co‐factor to regulate floral development. Development 135: 1235–1245.

Coen ES and Meyerowitz EM (1991) The war of the whorls: genetic interactions controlling flower development. Nature 353: 31–37.

Coen ES, Nugent JM, Lou DA et al. (1995) Evolution of floral symmetry. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 350: 35–38.

Corley SB, Carpenter R, Copsey L and Coen E (2005) Floral asymmetry involves an interplay between TCP and MYB transcription factors in Antirrhinum. Proceedings of the National Academy of Sciences of the USA 102: 5068–5073.

Costa MM, Fox S, Hanna AI, Baxter C and Coen E (2005) Evolution of regulatory interactions controlling floral asymmetry. Development 132: 5093–5101.

Dinneny JR, Yadegari R, Fischer RL, Yanofsky MF and Weigel D (2004) The role of JAGGED in shaping lateral organs. Development 131: 1101–1110.

Disch S, Anastasiou E, Sharma VK et al. (2006) The E3 ubiquitin ligase BIG BROTHER controls Arabidopsis organ size in a dosage‐dependent manner. Current Biology 16: 272–279.

van Doorn WG and Woltering EJ (2008) Physiology and molecular biology of petal senescence. Journal of Experimental Botany 59: 453–480.

Drea S, Hileman LC, de Martino G and Irish VF (2007) Functional analyses of genetic pathways controlling petal specification in poppy. Development 134: 4157–4166.

Feng X, Zhao Z, Tian Z et al. (2006) Control of petal shape and floral zygomorphy in Lotus japonicus. Proceedings of the National Academy of Sciences of the USA 103: 4970–4975.

Hileman LC, Drea S, Martino G, Litt A and Irish VF (2005) Virus‐induced gene silencing is an effective tool for assaying gene function in the basal eudicot species Papaver somniferum (opium poppy). Plant Journal 44: 334–341.

Honma T and Goto K (2001) Complexes of MADS‐box proteins are sufficient to convert leaves into floral organs. Nature 409: 525–529.

Irish VF (2009) Evolution of petal identity. Journal of Experimental Botany 60: 2517–2527.

Jack T, Fox GL and Meyerowitz EM (1994) Arabidopsis homeotic gene APETALA3 ectopic expression: transcriptional and posttranscriptional regulation determine floral organ identity. Cell 76: 703–716.

Kramer EM, Dorit RL and Irish VF (1998) Molecular evolution of genes controlling petal and stamen development: duplication and divergence within the APETALA3 and PISTILLATA MADS‐box gene lineages. Genetics 149: 765–783.

Kramer EM, Holappa L, Gould B et al. (2007) Elaboration of B gene function to include the identity of novel floral organs in the lower eudicot Aquilegia. Plant Cell 19: 750–766.

Krizek BA, Prost V and Macias A (2000) AINTEGUMENTA promotes petal identity and acts as a negative regulator of AGAMOUS. Plant Cell 12: 1357–1366.

Lamb RS, Hill TA, Tan QK and Irish VF (2002) Regulation of APETALA3 floral homeotic gene expression by meristem identity genes. Development 129: 2079–2086.

Li S, Lauri A, Ziemann M et al. (2009) Nuclear activity of ROXY1, a glutaredoxin interacting with TGA factors, is required for petal development in Arabidopsis thaliana. Plant Cell 21: 429–441.

Luo D, Carpenter R, Copsey L et al. (1999) Control of organ asymmetry in flowers of Antirrhinum. Cell 99: 367–376.

Luo D, Carpenter R, Vincent C, Copsey L and Coen E (1996) Origin of floral asymmetry in Antirrhinum. Nature 383: 794–799.

Mara CD and Irish VF (2008) Two GATA transcription factors are downstream effectors of floral homeotic gene action in Arabidopsis. Plant Physiology 147: 707–718.

de Martino G, Pan I, Emmanuel E, Levy A and Irish VF (2006) Functional analyses of two tomato APETALA3 genes demonstrate diversification in their roles in regulating floral development. Plant Cell 18: 1833–1845.

Nagasawa N, Miyoshi M, Sano Y et al. (2003) SUPERWOMAN1 and DROOPING LEAF genes control floral organ identity in rice. Development 130: 705–718.

Noda K, Glover BJ, Linstead P and Martin C (1994) Flower colour intensity depends on specialized cell shape controlled by a Myb‐related transcription factor. Nature 369: 661–664.

Parcy F, Nilsson O, Busch MA, Lee I and Weigel D (1998) A genetic framework for floral patterning. Nature 395: 561–566.

Pelaz S, Ditta GS, Baumann E, Wisman E and Yanofsky MF (2000) B and C floral organ identity functions require SEPALLATA MADS‐box genes. Nature 405: 200–203.

Pinyopich A, Ditta GS, Savidge B et al. (2003) Assessing the redundancy of MADS‐box genes during carpel and ovule development. Nature 424: 85–88.

Quattrocchio F, Verweij W, Kroon A et al. (2006) PH4 of Petunia is an R2R3 MYB protein that activates vacuolar acidification through interactions with basic‐helix‐loop‐helix transcription factors of the anthocyanin pathway. Plant Cell 18: 1274–1291.

Rijpkema AS, Royaert S, Zethof J et al. (2006) Analysis of the Petunia TM6 MADS box gene reveals functional divergence within the DEF/AP3 lineage. Plant Cell 18: 1819–1832.

Sablowski RW and Meyerowitz EM (1998) A homolog of NO APICAL MERISTEM is an immediate target of the floral homeotic genes APETALA3/PISTILLATA. Cell 92: 93–103.

Schwinn K, Venail J, Shang Y et al. (2006) A small family of MYB‐regulatory genes controls floral pigmentation intensity and patterning in the genus Antirrhinum. Plant Cell 18: 831–851.

Soltis DE, Chanderbali AS, Kim S, Buzgo M and Soltis PS (2007) The ABC model and its applicability to basal angiosperms. Annals of Botany 100: 155–163.

Souer E, Rebocho AB, Bliek M et al. (2008) Patterning of inflorescences and flowers by the F‐Box protein DOUBLE TOP and the LEAFY homolog ABERRANT LEAF AND FLOWER of Petunia. Plant Cell 20: 2033–2048.

Szecsi J, Joly C, Bordji K et al. (2006) BIGPETALp, a bHLH transcription factor is involved in the control of Arabidopsis petal size. EMBO Journal 25: 3912–3920.

Takeda S, Matsumoto N and Okada K (2004) RABBIT EARS, encoding a SUPERMAN‐like zinc finger protein, regulates petal development in Arabidopsis thaliana. Development 131: 425–434.

Takhtajan A (1991) Evolutionary Trends in Flowering Plants. New York: Columbia University Press.

Tilly JJ, Allen DW and Jack T (1998) The CArG boxes in the promoter of the Arabidopsis floral organ identity gene APETALA3 mediate diverse regulatory effects. Development 125: 1647–1657.

Verdonk JC, Haring MA, van Tunen AJ and Schuurink RC (2005) ODORANT1 regulates fragrance biosynthesis in Petunia flowers. Plant Cell 17: 1612–1624.

Wang Z, Luo Y, Li X et al. (2008) Genetic control of floral zygomorphy in pea (Pisum sativum L.). Proceedings of the National Academy of Sciences of the USA 105: 10414–10419.

Whipple CJ, Ciceri P, Padilla CM et al. (2004) Conservation of B‐class floral homeotic gene function between maize and Arabidopsis. Development 131: 6083–6091.

Whitney HM, Chittka L, Bruce TJ and Glover BJ (2009) Conical epidermal cells allow bees to grip flowers and increase foraging efficiency. Current Biology 19: 948–953.

Xing S, Rosso MG and Zachgo S (2005) ROXY1, a member of the plant glutaredoxin family, is required for petal development in Arabidopsis thaliana. Development 132: 1555–1565.

Zik M and Irish VF (2003) Global identification of target genes, regulated by APETALA3 and PISTILLATA floral homeotic gene action. Plant Cell 15: 207–222.

Further Reading

Drea S, Corsar J, Crawford B et al. (2005) A streamlined method for systematic, high resolution in situ analysis of mRNA distribution in plants. Plant Methods 1: 8.

Gould B and Kramer EM (2007) Virus‐induced gene silencing as a tool for functional analyses in the emerging model plant Aquilegia (columbine, Ranunculaceae). Plant Methods 3: 6.

Hileman LC and Irish VF (2009) More is better: the uses of developmental genetic data to reconstruct perianth evolution. American Journal of Botany 96: 83–95.

Irish VF (2008) The Arabidopsis petal: a model for plant organogenesis. Trends in Plant Science 13: 430–436.

Ronse De Craene LP (2007) Are petals sterile stamens or bracts? The origin and evolution of petals in the core eudicots. Annals of Botany 100: 621–630.

Theissen G and Saedler H (2001) Plant biology. Floral quartets. Nature 409: 469–471.

Weberling F (1989) Morphology of Flowers and Inflorescences. Cambridge: Cambridge University Press.

Wege S, Scholz A, Gleissberg S and Becker A (2007) Highly efficient virus‐induced gene silencing (VIGS) in California poppy (Eschscholzia californica): an evaluation of VIGS as a strategy to obtain functional data from non‐model plants. Annals of Botany (London) 100: 641–649.

Wellmer F, Riechmann JL, Alves‐Ferreira M and Meyerowitz EM (2004) Genome‐wide analysis of spatial gene expression in Arabidopsis flowers. Plant Cell 16: 1314–1326.

Whipple CJ, Zanis MJ, Kellogg EA and Schmidt RJ (2007) Conservation of B class gene expression in the second whorl of a basal grass and outgroups links the origin of lodicules and petals. Proceedings of the National Academy of Sciences of the USA 104: 1081–1086.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Drea, Sinéad(Apr 2010) Petals. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0002065.pub2]