Flow Cytometry of Protoplasts from C4 Plants

Abstract

In leaves from species with the C4 dicarboxylic acid pathway of photosynthesis, two different chloroplast types exist: the mesophyll (MES) and the bundle sheath (BS) chloroplasts. In most C4 plants, MES and BS chloroplasts differ in their PSII/PSI ratios (1) and, hence, exhibit different chlorophyll fluorescence intensities at wavelengths smaller than 700 nm (R) relative to those at wavelengths longer than 710 nm (FR). Earlier, we analysed by flow cytometry the chloroplasts from C4 species by measuring the R and the FR fluorescence (2,3). Flow cytometric sorting yielded essentially pure MES and BS chloroplasts. Fluorescence spectroscopy of the pure chloroplast fractions revealed that in BS chloroplasts from many NADP-malic enzyme-type C4 plants, PSII is present in significant amounts and that its excitation energy is efficiently transferred to PSI.