FLUORESCENCE LIFETIMES OF CHLORELLA-PYRENOIDOSA

The fluorescence decay of C. pyrenoidosa was investigated under a variety of conditions in the ps and ns time regions. Most of the fluorescence is accounted for by an expression of the form I(t) = I0 exp.sbd.(AT + Bt1/2) though an additional exponential term is required to include a weak component of lifetime 32 ps observable only at the higher pulse intensities. This interpretation reconciles earlier and apparently conflicting data. The weak 32 ps component may be associated with Photosystem I, although the possibility that it is an artifact of the high intensity pulses used cannot be excluded at present. The main fluorescence, described by the equation above, is attributed to the antenna chlorophyll and is of the form which would be expected from a single light harvesting array with trapping at randomly distributed sites.