In vivo measurement of spectroscopic and photochemical properties of intact leaves using the 'mirage effect'

Michel Havaux, Lucie Lorrain, Roger M. Leblanc

Research output: Contribution to journalArticle

17 Scopus citations


This paper describes a new, highly sensitive, method for in vivo studies of photosynthesis based on the 'mirage effect' in which thermal energy dissipation from intact leaves, illuminated with intensity-modulated light, is sensed through the periodic deflection of a laser beam propagating along the leaf surface. The photothermal deflection technique allows one to rapidly estimate the gross efficiency of photochemical energy storage by comparing the heat emission signal with and without an additional strong, photosynthetically saturating, non-modulated light. In pea leaves, the maximal storage efficiency at low light intensities was shown to approach 55%. The general utility of this simple photothermal method is illustrated by examining the variation of the deflection signal under different conditions. The spectral resolution of this new method is shown to be much higher than that of the photoacoustic method.

Original languageEnglish (US)
Pages (from-to)395-399
Number of pages5
JournalFEBS letters
Issue number2
StatePublished - Jul 3 1989



  • Intact leaf
  • Mirage effect
  • Photoacoustic technique
  • Photosynthesis
  • Photothermal deflection technique

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

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