Hello Darkness, My Old Friend: A Tutorial of Nanda-Hamner Protocols

Nicholas M. Teets, Megan E. Meuti

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Plants and animals use circadian and photoperiodic timekeeping mechanisms to respond to daily and seasonal changes in light:dark and appropriately coordinate their development. Although the mechanisms that may connect the circadian and photoperiodic clock are still unclear in many species, researchers have been using Nanda-Hamner protocols for decades to elucidate how seasonal time is measured and determine whether seasonal responses have a circadian basis in a given species. In this brief tutorial we describe how to design and interpret the results of Nanda-Hamner experiments, and provide suggestions on how to use both Nanda-Hamner protocols and modern molecular experiments to better understand the mechanisms of seasonal timekeeping.

Original languageEnglish
Pages (from-to)221-225
Number of pages5
JournalJournal of Biological Rhythms
Issue number3
StatePublished - Jun 2021

Bibliographical note

Funding Information:
We thank Dr. Mary Harrington, editor of Journal of Biological Rhythms, for inviting us to prepare this tutorial. We also thank an anonymous reviewer for pointing out an important reference for the paper. This work is supported by Hatch Project 1010996 from the USDA National Institute of Food and Agriculture and NSF Grants OIA-1826689 and OPP-1850988 to N.M.T. and NSF Grant IOS-1944324 to M.E.M.

Publisher Copyright:
© 2021 The Author(s).


  • Nanda-Hamner protocol
  • circadian rhythms
  • external coincidence model
  • hourglass model
  • photoperiodism

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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