Abstract: Cotton ( Gossypium hirsutum L. ) stigma, style and ovule segments were fixed pre- and post-pollination in glutaraidehyde and osmium solutions containing potassium pyroantimonate, processed with conventional dehydration and infiltration procedure, and embedded in Epon 821 resin. To identify the element constitution of the pyroanti-monate deposits in the samples, wave-and energydispersive X-ray microanalyses were employed, and it was confirmed that the deposits were truly calcium pyroantimonate. Transmission electron microscopic observations revealed that the deposits were more abundant at the whole pollen tube track as compared with the adjacent tissues. They were mainly localized in the apoplast system, i.e. the intercellular matrix of the stigmatic tissue, the outer cell wall layers of stylar transmitting tissue, the intercellular openings and gaps of micropyle, and the degenerated column of nucellus, h was reported that these apoplast spaces were just the positions where pollen tabes grew. The pollen tube tip growing in the micropyle was also rich in calcium, which was especially locaiized at the new wall, vesicles and mitochondria. All these observations suggested that calcium in the gynoecium tissues may play an suggested important role in the pollen tube growth in situ.

Key words: Gossypium hirsutum, Gynoecium, Pollen tube, Calcium, Ultracytochemical localization