INCREASED HEAT EMISSION IN PHOTOSYNTHETIC APPARATUS OF RYE SUBJECTED TO LIGHT STRESS

The calorimetric technique was applied to monitor thermal energy dissi pation in leaves of rye (Secale cereale L.) illuminated with increasin g light intensity. Illumination with light of higher intensity than th at at which plants were grown before the experiment was followed by th e increase of thermal energy dissipation. Such a phenomenon, considere d as a photoprotection of photosynthetic apparatus against overexcitat ion and photodamage, was correlated with the activity of the xanthophy ll cycle. Possible photophysical mechanisms linking violaxanthin de-ep oxidation within the xanthophyll cycle and increased heat emission are discussed briefly.