C4 syndrome of the species in theDichotomiflora group of the genusPanicum (Gramineae)

Leaf anatomy, pattern of post-illumination CO₂ burst (PIB) and activity of three C₄-acid decarboxylating enzymes in C₄ photosynthesis were investigated with the leaves of five species in theDichotomiflora group of the genusPanicum. All species had mestome sheaths, exhibited the sharp pattern of PIB in less than 30 sec of darkness and were classified as NAD-malie enzyme species biochemically. However, they clearly fell into two groups according to the difference in chloroplast location in bundle sheath cells (BSC).P. coloratum var.makarikariense, P. lanipes andP. stapfianum had centripetal chloroplasts, whereasP. laevifolium andP. longijubatum had centrifugal chloroplasts, whereas cv. Kabulabula and cv. Solai had centrifugal chlorplasts. The results indicate that theDichotomiflora group had the two leaf anatomical variations of NAD-malic enzyme species. In addition, the results onP. coloratum suggest that this species may be divided into two separate species by chloroplast location in BSC. The ultrastructural features of leaves ofP. dichtomiflorum, NAD-malic enzyme species with centrifugal chloroplasts, were also investigated. Chloroplasts in BSC had well-developed grana, and numerous large mitochondria with extensively developed internal membrane structure were restricted to the area between the chloroplsts and the vacuole in BSC.