High-magnification CLSM detection of NO with DAF-2 DA at different developmental stages of the olive flower. A: projection of section stacks of the stigma surface at stage 3. The fluorescence localizes in association with the stigmatic papillae. B and C: projection of section stacks -and an enlarged view- of the stigmatic surface at the end of stage 3. Green fluorescence labels the stigmatic papillae and the pollen surface, mainly the apertural region and the emerging pollen tube. D and E: optical section -and an enlarged view- of the stigmatic surface at stage 4. NO extensively accumulates in the stigmatic papillae, and in the pollen grains, the pollen tubes and the exudate. F: projection of section stacks of the dehiscent anther surface at stage 4. NO labelling occurs in the dehiscent loculi, associated to the numerous pollen grains. Ap: aperture; Ex: exudate; p: papillae; Pg: pollen grain; Pt: pollen tube.