Panicum milioides, a Gramineae plant having Kranz leaf anatomy without C4-photosynthesis

Light and electron microscopic observations of the leaf tissue of Panicum milioides showed that the bundle sheath cells contained a substantial number of chloroplasts and other organelles. The radial arrangement of chlorenchymatous bundle sheath cells, designated as Kranz leaf anatomy, has been considered to be specific to C4 plants. However, photosynthetic 14CO2 fixation and 14CO2 pulse-and-chase experiments revealed that the reductive pentosephosphate pathway was the main route operating in leaves of P. milioides. The interveinal distance of the leaves was intermediate between C3and C4Gramineae species. These results indicate that P. milioides is a natural plant species having chracteristics intermediate between C3 and C4 types.