Quantitative Measurements of Phosphofructokinase in the Shoot Apical Meristem, Leaf Primordia, and Leaf Tissues of Dianthus chinensis L.
Phosphofructokinase (EC 2.7.1.11) activity in the apical meristem, leaf primordia, and leaf tissues (epidermis, mesophyll, xylem, phloem) of Dianthus chinensis L. was determined. These data show that activity on a dry weight per hour basis was about 1000 millimoles in the apical meristem and two youngest primordia, and declined to 150 millimoles in the mesophyll of the sixth leaf pair and to 80 millimoles in older leaves just expanded out of the bud. On a cell per hour basis, the activity increased from 75 femtomoles in cells of the apical meristem and leaf primordia to 1.5 picomoles in the mesophyll of the sixth leaf pair. However, on a cell volume (cubic micrometers) per hour basis, the opposite was true. The results indicate that (a) on a dry weight or unit cell volume basis the capacity for glycolysis declines during leaf development and that (b) within the apical meristem, incipient primordia are not associated with phosphofructokinase activity greater than adjacent areas of the meristem. In comparison to glucose-6-phosphate dehydrogenase activity previously measured in equivalent samples (Croxdale, Outlaw 1983 Planta 157: 289-297), the capacity of the glycolytic pathway is greater than the pentose phosphate pathway in the apical meristem and two youngest pair of primordia. By the time leaves are six plastochrons old, the capacity for carbohydrate oxidation by the hexose monophosphate shunt exceeds that by glycolysis.
Croxdale
J G
JG
Department of Botany, University of Wisconsin, Madison, Wisconsin 53706.