Formation of prolamellar bodies without correlative accumulation of protochlorophyllide or chlorophyllide in pine cotyledons

Abstract

Chloroplast formation and accumulation of chlorophyllous pigments were studied in pine cotyledons ( Pinus jeffreyi) during germination in complete darkness or under continuous light. During the first days of germination (in the light and in the dark), cotyledons grew inside the seed; at this moment, no membranes were visible in proplastids and no chlorophyllous pigments could be detected. When the radicle broke the seed integuments, the cotyledons had developed green plastids. These contained crystalline prolamellar bodies as well as lamellae and grana. The same plastid structure was found in fully expanded cotyledons from dark-brown pine seedlings. Under continuous light, even when cotyledons emerged from the seed integuments, the plastids still contained prolamellar bodies. The prolamellar bodies remained for several days but gradually decreased and finally disappeared. Analysis of pigment content could not establish a correlation between the formation of prolamellar bodies and the accumulation of protochlorophyllide a or/and chlorophyllide a.