Simultaneous occurrence of C3 and C4 photosyntheses in relation to leaf position in Mollugo nudicaulis

Abstract

SINCE the discovery of C4 photosynthesis1,2 higher plants have been categorised into C3 plants, which form 3-phosphoglycerate (PGA) as the first labelled intermediate, and C4 plants, which form 4-carbon acids as the predominant early photosynthetic products, C4 plants can also be distinguished by features such as Kranz leaf anatomy, low photorespiration, high photosynthetic efficiency and reduced 13C discrimination3. Although 943 C4 plants are known to be distributed among 18 families, only 18 genera from 10 families include both C3 and C4 plants4. Kennedy and Laetsch5 described Mollugo verticillata as intermediate for C3 and C4 photosynthesis. But Brown and Brown6 felt that it was a typical C3 plant. Recently three Panicum species (P. milioides, P. hians and P. laxum) have been found to have photosynthetic characteristics intermediate between C3 and C4 plants6–8. We now report that a single plant of Mollugo nudicaulis can have some leaves with C3 characteristics and others with C4 characteristics according to their position on the stem.