Photoinhibition of photosynthesis in intact kiwifruit (Actinidia deliciosa) leaves: Effect of temperature

✍ Scribed by D. H. Greer; W. A. Laing; T. Kipnis

• Publisher: Springer-Verlag
• Year: 1988
• Tongue: English
• Weight: 680 KB
• Volume: 174
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00394766

✦ Synopsis

Photoinhibition of photosynthesis was induced in attached leaves of kiwifruit grown in natural light not exceeding a photon flux density (PFD) of 300 gmol-m -2. s-~, by exposing them to a PFD of 1 500 gmol. m -2. s-1. The temperature was held constant, between 5 and 35 ~ C, during the exposure to high light. The kinetics of photoinhibition were measured by chlorophyll fluorescence at 77K and the photon yield of photosynthetic O2 evolution. Photoinhibition occurred at all temperatures but was greatest at low temperatures. Photoinhibition followed pseudo first-order kinetics, as determined by the variable fluorescence (F,) and photon yield, with the long-term steadystate of photoinhibition strongly dependent on temperature whereas the observed rate constant was only weakly temperature-dependent. Temperature had little effect on the decrease in the maximum fluorescence (Fro) but the increase in the instantaneous fluorescence (Fo) was significantly affected by low temperatures in particular. These changes in fluorescence indicate that kiwifruit leaves have some capacity to dissipate excessive excitation energy by increasing the rate constant for non-radiative (thermal) energy dissipation although temperature apparently had little effect on this. Direct photoinhibitory damage to the photosystem 1I reaction centres was evident by the increases in Fo and extreme, irreversible damage occurred at the lower temperatures. This indicates