Variations in the dorso-ventral organization of leaf structure and Kranz anatomy coordinate the control of photosynthesis and associated signalling at the whole leaf level in monocotyledonous species

Abstract

Photosynthesis and associated signalling are influenced by the dorso-ventral properties of leaves. The degree of adaxial/abaxial symmetry in stomatal numbers, photosynthetic regulation with respect to light orientation and the total section areas of the bundle sheath (BS) cells and the surrounding mesophyll (M) cells on the adaxial and abaxial sides of the vascular bundles were compared in two C4 [Zea mays (maize) and Paspalum dilatatum] and one C3 [Triticum turgidum (Durum wheat)] monocotyledonous species. The C3 leaves had a higher degree of dorso-ventral symmetry than the C4 leaves. Photosynthetic regulation was the same on each side of the wheat leaves, as were stomatal numbers and the section area of the BS relative to that of the M cells (BS/M section area ratio). In contrast, photosynthetic regulation in maize and P. dilatatum leaves showed a marked surface-specific response to light orientation. Compared to the adaxial sides of the C 4 monocotyledonous leaves, the abaxial surfaces had more stomata and the BS/M section area ratio was significantly higher. Differences in dorso-ventral structure, particularly in Kranz anatomy, serve not only to maximize photosynthetic capacity with respect light orientation in C4 monocotyledonous leaves but also allow adaxial and abaxial-specific signalling from the respective M cells. © 2009 Blackwell Publishing Ltd.