C₃‐C₄ PHOTOSYNTHESIS IN THE GENUS MOLLUGO: STRUCTURE, PHYSIOLOGY AND EVOLUTION OF INTERMEDIATE CHARACTERISTICS

Abstract

The genus Mollugo has been reported to have species which are C 4 plants and a C 3 ‐C 4 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 C 3 and C 4 plants. Most notable among the variable C 3 ‐C 4 features are C 4 ‐like bundle sheath cells, along with a C 3 ‐like arrangement of palisade and spongy parenchyma. M. nudicaulis appeared to have lower photorespiration based on its CO 2 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.