The relationship between the lifetime and yield of the 735 nm fluorescence of chloroplasts at low temperatures.

The lifetime and relative yield of the 735 nm fluorescence of chloroplasts, over a range of low temperatures (-60 to -196 degrees C) where the yield of fluorescence changes markedly, were found to be directly proportional. It is concluded that the species of chlorophyll responsible for the 735 nm fluorescence, C-705, is present over the entire temperature range but is less fluorescent at the higher temperatures because of greater energy transfer to P-700. It is also concluded from attempts to measure the rise-time of the 735 nm fluorescence at -196 degrees C that the rise-time is less than 50 ps.