C3 and C4 leaf anatomy types in Camphorosmeae (Camphorosmoideae, Chenopodiaceae)

Complementary to our previous project on the molecular phylogeny of Camphorosmeae, the leaf anatomy of ca. 35 species including all non-Australian and selected Australian species was studied by use of light microscopy. Nine anatomical leaf types were described, compared to previous classifications, and discussed with regard to their putative evolution on the background of phylogenetic trees. Particular emphasis was given to the relationships between the C₃ and C₄ leaf types: Chenolea type (C₃), Eokochia type (C₃), Neokochia type (C₃), Sedobassia type (C₃/C₄ intermediate), Bassia prostrata type (C₄), B. muricata type (C₄), B. eriantha type, B. lasiantha type (C₄), Camphorosma type (C₄). The main results and conclusions were: (1) Two unusual new C₃ leaf types: Chenolea with microfenestrate chlorenchyma, Eokochia with unique complex vascular bundles; (2) Sedobassia interpreted as anatomically C₃/C₄ intermediate by kranz-like bundle sheath cells is the first C₃/C₄ intermediate in Camphorosmeae and found in a derived position; (3) Neokochia type detected as the likely starting point for all four C₄ leaf types and for the C₃/C₄ intermediate; (4) hypodermis of C₄ types originated from outermost chlorenchyma layer of C₃ types and lost multiple times during further evolution; (5) atriplicoid Bassia. lasiantha type without water storage tissue evolved from kochioid B.muricata type; (6) two independent gains of C₄ photosynthesis, one in Bassia and one in Camphorosma; (7) depending on the lineage, leaf architecture remains comparatively stable (Australian Camphorosmeae) or shows an unexpected plasticity (Bassia scoparia group).