C 3 -C 4 Photosynthesis in the Genus Mollugo: Structure, Physiology and Evolution of Intermediate Characteristics

Abstract

The genus Mollugo has been reported to have species which are C4 plants and a C3-C4 intermediate. In the present paper, we report on the anatomy and photosynthetic physiology of three additional species in the Molluginaceae, M. pentaphylla, M. nudicaulis, and M. lotoides, all of which possess some anatomical and physiological features of both C3 and C4 plants. Most notable among the variable C3-C4 features are C4-like bundle sheath cells, along with a C3-like arrangement of palisade and spongy parenchyma. M. nudicaulis appeared to have lower photorespiration based on its CO2 compensation point and lower oxygen sensitivity of photosynthesis. The occurrence of polyploidy within this group of plants and its relationship to lower photorespiration or evolution of these species is discussed.