Pollen morphological studies in Amaranthaceae s.lat. (incl. Chenopodiaceae) and their taxonomic significance: A review

Abstract Amaranthaceae s.lat. is a stenopalynous family showing, in contrast, a considerable phenotypic diversity for macromorhological characters. A total of one quantitative and seven qualitative characters were reviewed in an attempt to assess their taxonomic implications. The presence of unique shape class, pore membrane sculpturing, anulopunctate tectum and pore borders clearly distinguished the subfamilies Amaranthoideae and Gomphrenoideae (Amaranthaceae sensu stricto) from the rest of the subfamilies of Amaranthaceae s.lat. Metareticulate exines are present exclusively in the subfamily Gomphrenoideae, in one genus of the subfamily Corispermoideae and encountered in one species – belonging to subfamily Polycnemoideae. Pore numbers although reported as a useful diagnostic feature, showed considerable intra-specific variation. The two basic pollen-types (Amaranthus-type and Gomphrena-type) within the subfamilies Amaranthoideae and Gomphrenoideae are quite distinct and gained broad acceptance, whereas the pollen types investigated for the rest of the subfamilies (belonging to Chenopodiaceae) are diverse and intricate. With the exception of Anthochlamys-type (related to Gomphrena-type), it was noticed that either members of one type constitute members of different subfamilies, or members of the same subfamily were scattered in different pollen-types, highlighting difficulties in recognising distinctive pollen-types in these subfamilies. The pollen-types within the subfamilies Betoideae, Camphrosomoideae, Chenopodioideae, Corispermoideae, Salicornioideae, Salsoloideae, Suaedoideae and Polycnemoideae are diverse and do not support their differentiation. Members of the subfamily Polycnemoideae share similarities with Amaranthaceae s.str. rather than members of the family Chenopodiaceae.