Delayed fluorescence(DF) is the luminescence phenomenon of plant photosynthestic apparatus(after) stop illuminating

it is also called delayed light emission(DLE) for that it has the same wave with fluorescence and is delayed after fluorescence.DF is not only the internal fluorescence probe for the efficiency of charges separation in the P680

but also the useful implement to distinguish that photosynthesis produced on(antenna) or on electron transfer chain

hence

it is used widely in study on the photosynthestic capacity of plant and on the stress effects of environment on plant.Research of the mechanism for delayed fluorescence origin plays an important role in the application of DF.Based on the Charge Recombination Theory(CRT)

the mechanism for delayed fluorescence origin is theoretically analyzed in this paper.The decay kinetic equation of DF can be well fitted by poly-exponent.We postulated that constant "C" is a symbol for component of delayed fluorescence

whose lifetime is more longer than other component

and it is come form the backward transport electron from PSⅠto PSⅡ and the recombination of P680

+

.Fortunately

we successfully and firstly testified that the third component(constant

C

) with lifetime(τ

>

5s) much greater than the time of the registration period(which is presented as a constant)

is corresponds to the backward transport electron from PSⅠand the recombination of P680

+

.The experimental evidence has significance on the study on the mechanism for the delayed fluorescence origin of higher plant chloroplast

it also provides a quantitative analysis standard for the rapid dermination of the photosynthestic rate of plant by using plant light-induced delay fluorescence.