Palisade Tissue Chloroplasts and Spongy Tissue Chloroplasts in Spinach: Biochemical and Ultrastructural Differences

摘要

Palisade tissue chloroplasts (P-Chlts) and spongy tissue chloroplasts (S-Chlts) were separately isolated from spinach leaves, and their photosynthetic properties were compared. The following results were obtained:(1) At saturating light, the activities of overall electron transport and CO2fixation in P-Chlts were respectively 1.6–2.0 and 2.5–3.0 times higher than those in S-Chlts on a Chl basis.(2) The contents of PS I and PS II reaction centers (P700 and 47 kDa polypeptide, respectively) were slightly higher in P-Chlts than in S-Chlts, while the contents of plastoquinone, Cytf, plastocyanin, ferredoxin, ferredoxin-NADP+reductase, coupling factor and ribulose-bisphosphate carboxylase were 1.6–2.2 times higher in P-Chlts than in S-Chlts on a Chl basis.(3) Electron microscopic examination of chloroplast ultrastructure showed that S-Chlts have highly stacked grana accompanied by higher proportion of appressed thylakoids relative to non-appressed thylakoids, while P-Chlts have poorly stacked grana. The volume ratio of thylakoids to stroma was higher in S-Chlts than in P-Chlts.These results indicate that mesophyll chloroplasts adapt to the light environment within a leaf in a similar way that the sun and shade plant chloroplasts adapt to the light environment within a c