Environmental control of sepalness and petalness in perianth organs of waterlilies: A new Mosaic Theory for the evolutionary origin of a differentiated perianth

Kate A. Warner, Paula J. Rudall, Michael W. Frohlich

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

The conventional concept of an 'undifferentiated perianth', implying that all perianth organs of a flower are alike, obscures the fact that individual perianth organs are sometimes differentiated into sepaloid and petaloid regions, as in the early-divergent angiosperms Nuphar, Nymphaea, and Schisandra. In the waterlilies Nuphar and Nymphaea, sepaloid regions closely coincide with regions of the perianth that were exposed when the flower was in bud, whereas petaloid regions occur in covered regions, suggesting that their development is at least partly controlled by the environment of the developing tepal. Green and colourful areas differ from each other in trichome density and presence of papillae, features that often distinguish sepals and petals. Field experiments to test whether artificial exposure can induce sepalness in the inner tepals showed that development of sepaloid patches is initiated by exposure, at least in the waterlily species examined. Although light is an important environmental cue, other important factors include an absence of surface contact. Our interpretation contradicts the unspoken rule that 'sepal' and 'petal' must refer to whole organs. We propose a novel theory (the Mosaic theory), in which the distinction between sepalness and petalness evolved early in angiosperm history, but these features were not fixed to particular organs and were primarily environmentally controlled. At a later stage in angiosperm evolution, sepaloid and petaloid characteristics became fixed to whole organs in specific whorls, thus reducing or removing the need for environmental control in favour of fixed developmental control.

Original languageEnglish (US)
Pages (from-to)3559-3574
Number of pages16
JournalJournal of experimental botany
Volume60
Issue number12
DOIs
StatePublished - Aug 2009

All Science Journal Classification (ASJC) codes

  • Physiology
  • Plant Science

Fingerprint Dive into the research topics of 'Environmental control of sepalness and petalness in perianth organs of waterlilies: A new Mosaic Theory for the evolutionary origin of a differentiated perianth'. Together they form a unique fingerprint.

  • Cite this