Leaf structure and translocation of dry matter in a C3 and a C 4 grass.

Dry weight analyses and (14)CO2 were used to study translocation in leaves of the C3 grass Lolium temulentum L. and the C4 grass Panicum maximum Jacq. and the results related to the distribution and amount of phloem in the lamina. The rate of specific mass transfer rose from the tips to the bases of leaf blades, in both species high rates were recorded. Major veins were responsible for the bulk of longitudinal translocation and minor veins were important in collecting and loading photosynthate. Transverse veins stored (14)C-assimilate and may have coordinated the functioning of the longitudinal veins. The bearing of the results on the mechanism of translocation is discussed.