STIGMA OF NICOTIANA: ULTRASTRUCTURAL AND BIOCHEMICAL STUDIES

Abstract

The aim of the present study has been to elucidate further the cytology of the glandular stigma of Nicotiana tabacum , the mechanism of the secretory process during stigma development and the biochemical composition of the exudate. The stigma consists of two distinct zones: a glandular zone formed by the papillae and 2–3 layers of cells (basal cells) immediately below them, and a non‐glandular region formed by vacuolated cells which are in continuity with the transmitting tissue. The stigmatic exudate is a complex mixture of different chemical compounds such as proteins, saccharides, fatty acids and phenols. The role of stigma secretion is discussed in relation to pollen activation, recognition and pollen tube growth.