The Specific Density of a Leaf as a Characteristic of the Photosynthetic Apparatus

At early stages of ontogeny (up to 50–60% of the maximum leaf area) of wheat (Triticum aestivumL.), meadow fescue (Festuca pratensisHuds.), reed fescue (F. arindinaceaSchreb.), and sugar beet (Beta vulgarisL. var. saccharifera(Alef) Krass), there is a correlation between changes in the specific leaf density (SLD); photosynthetic CO2assimilation rate; activity of the key photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39); and the concentrations of chlorophyll (Chl) a, Chl b, carotenoids, and soluble leaf proteins. However, the SLD does not correlate with the activity of phospho(enol)pyruvate carboxylase (EC 4.1.1.31). Senescence was accompanied by a decrease in the leaf SLD. Treatment with cytokininomimetics (6-benzylaminopurine and Metribuzin) caused an increase in the SLD. The specific leaf density is suggested to be a structural and functional characteristic of the photosynthetic apparatus of agricultural plants.