Comparative Anatomy and Morphology of Leaves between C3 and C4 Species in Panicum

Anatomical and morphological structures of leaf blades werecompared between C₃ and C₄ species in Panicum. Inter-specificvariation of stomatal density, longitudinal vein density andmesophyll thickness was highly correlative either plus or minuswithin respective groups. The two groups could not be distinguishedby a single character, since the variation ranges overlappedeach other. However, the quantitative relations between veindensity and the other two characters differentiated the twogroups well. In C₃, stomatal density seemed to be a primaryfactor for regulating water balance, while in C₄ vein systemwas considered to be important for the regulation. The specieswith intermediate photosynthesis behaved similar to the C₃ species.In the C₃ group, correlative variation was observed betweenleaf width, leaf angle and the three characters mentioned above.Variation of light-receiving area due to the changes of widthand angle of leaf blades was considered to be one of the adaptivestrategies of this group. Increase of light-receiving area wasin connection with the thinning of leaves. On the other hand,in the C₄ correlations between length, width and angle of leaveswere low. Such loose character correlation may be achieved byits efficiency of CO₂ utilization and its well developed veinsystems. Besides, NAD-me type species tended to have relativelylower stomatal and vein densities as compared with the otherdecarboxylation types in this group. Panicum, photosynthesis, C₃, C₄, decarboxylation types, leaf, stomata, vein