Petals

Abstract

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.