Assessing photosystem I and II distribution in leaves from C4 plants using confocal laser scanning microscopy

Abstract

ABSTRACTImages of chlorophyll fluorescence emitted at wavelengths above and below 700 nm were recorded from leaf sections of C4 species using confocal laser scanning microscopy (LSM). We investigated species exhibiting both NAD‐malic enzyme (NAD‐ME) C4 photosynthesis and NADP‐malic enzyme (NADP‐ME) C4 photosynthesis. Comparing LSM fluorescence of leaf sections with flow‐cytometrically determined fluorescence from individual chloroplasts revealed that LSM fluorescence was distorted by the optical properties of leaf sections. Leaf section fluorescence, when corrected by transmission data derived from light transmission images, agreed with flow cytometry data. The corrected LSM fluorescence yielded information on the distribution of the individual photosystems in the C4 leaf sections: PSII concentrations in bundle sheath cells were elevated in NAD‐ME species but diminished in most of the NADP‐ME species investigated. The NADP‐ME species, Arundinella hirta, however, showed normal PSII and increased PSI concentration in bundle sheath chloroplasts. Finally, a gradient of PSI was observed within the bundle sheath cells from Euphorbia maculata.