LEAF ANATOMY AND SUBGENERIC AFFILIATIONS OF C-3 AND C-4 SPECIES OF SUAEDA (CHENOPODIACEAE) IN NORTH-AMERICA

The halophytic genus Suaeda (Chenopodiaceae) includes species with the C-3 and C-4 photosynthetic pathways. North American species of this g enus were investigated to determine whether C-3 and C-4 leaf anatomy a re consistent within the two sections of Suaeda, Chenopodina and Limbo germen, present on this continent. All species from section Chenopodin a were found to possess C-3 anatomy, whereas all species from section Limbogermen were found to he C-4 species, Characteristics of leaf anat omy and chloroplast ultrastructure are similar to those reported from C-3 and C-4 species. respectively, from the Eastern Hemisphere. All sp ecies from section Limbogermen have the suaedoid type of leaf anatomy, characterized by differentiation of the mesophyll into palisade paren chyma and a chlorenchymatous sheath surrounding central water-storage tissue, as well as leaf carbon isotope ratios (delta(13)C) of above -2 0. All species from section Chenopodina have austrobassioid leaf anato my without a chlorenchymatous sheath and delta(13)C values of below -2 0. According to our literature review, the photosynthetic pathway has now been reported for about half (44) of the Suaeda species worldwide. The C-3 and C-4 photosynthetic syndromes are with few exceptions dist ributed along sectional or subsectional lines. These findings throw ne w light on the infrageneric taxonomy of this genus.