Chlorophyll synthesis in dark-crown pine primary needles

The pigment content of dark-grown primary needles of Pines jeffreyi L. and Pines sylvestris L. was determined by highperformance liquid chromatography . The state of protochlorophyllide a and of chlorophylls during dark growth were analyzed by in situ 77 K fluorescence spectroscopy. Both measurements unambiguously demonstrated that pine primary needles are able to synthesiz e chlorophyll in the dark. Norflurazon strongly inhibited both carotenoid a nd chlorophyll synthesis. Needles of plants treated with this inhibitor had low chlorophyll content, contained only traces of xanthophylls, and accumu lated carotenoid precursors. The first form of chlorophyll detected in youn g pine needles grown in darkness had an emission maximum at 678 nm. Chlorop hyll-protein complexes with in situ spectroscopic properties similar to tho se of fully green needles (685, 695, and 735 nm) later accumulated in untre ated plants, whereas in norflurazon-treated plants the photosystem I emissi on at 735 nm was completely lacking. To better characterize the light-depen dent chlorophyll biosynthetic pathway in pine needles, the 77 K fluorescenc e properties of in situ protochlorophyllide a spectral forms were studied. Photoactive and nonphotoactive protochlorophyllide a forms with emission pr operties similar to those reported for dark-grown angiosperms were found, b ut excitation spectra were substantially red shifted. Because of their lowe r chlorophyll content, norflurazon-treated plants were used to study the pr otochlorophyllide a photoreduction process triggered by one light flash. Th e first stable chlorophyllide photoproduct was a chlorophyllide a form emit ting at 688 nm as in angiosperms. Further chlorophyllide a shifts usually o bserved in angiosperms were not detected. The rapid regeneration of photoac tive protochlorophyllide a from nonphotoactive protochlorophyllide after on e flash was demonstrated.