Heat-induced changes of chlorophyll fluorescence in intact leaves correlated with damage of the photosynthetic apparatus

✍ Scribed by Ulrich Schreiber; Joseph A. Berry

• Publisher: Springer-Verlag
• Year: 1977
• Tongue: English
• Weight: 583 KB
• Volume: 136
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00385990

✦ Synopsis

Methods were developed to measure chlorophyll fluorescence yield of intact leaf tissue during heat treatment under varying conditions of light intensity and photosynthetic activity. Fluorescence yield of a dark-adapted leaf increases by 2- to 3-fold with an increase of temperature into the region where heat-damage occurs. The temperatures of the fluorescence transition correlate well with the temperatures where quantum yield of CO2 fixation is irreversibly depressed. Fluorescence-temperature (F-T) curves allow ranking of different species according to their heat sensitivity. Within a single species acclimation to different growth temperatures is reflected by shifts of the transition temperatures in the F-T curves. When F-T curves are recorded in the steady light states at increasing light intensities, substantial shifts (up to 6°C) of transition temperatures to higher values are observed. Quantum yield measurements of CO2 fixation confirm that hight-light conditions protect from heat-damage. It is suggested that chlorophyll acts as an intrinsic fluorescence probe of the thylakoid membrane and responds to the same changes which cause irreversible denaturation of photosynthetic enzymes.