The protochlorophyllide transformation process was investigated by using comparative analysis of 77 K fluorescence spectral changes occurring in isolated bundle sheath (BS) cells of etiolated Zea mays leaves after being exposed to a 200 ms saturating flash. Deconvolution analysis of the fluorescence spectra showed essential differences in the ratio of protochlorophyll(ides) and chlorophyll(ides) spectral forms indicating for BS cells to have a characteristic pathway of protochlorophyllide transformation. Bundle sheath cells showed a high ratio between non-photoactive protochlorophyll(ide)-F632 and photoactive protochlorophyllide-F655. In those cells, the 200 ms flash triggered a preferential formation of chlorophyll(ide)-F675 which remained stable in the dark for at least 90 min. Isolated BS cells showed an accumulation of chlorophyll(ide)-F675 resulting in the formation of inactive photosystem II. However for mesophyll cells of intact leaves, it was found to have a high ratio between photoactive and non-photoactive protochlorophyll(ide), showing the succession of chlorophyll(ide) forms usually known in C 3 plants. Protochlorophyllide phototransformation pathway in BS cells related to early stages of plastid differentiation triggered by light may indicate specific conditions for PSII assembly process leading to inactive PSII forms.