The activity of enzymes characteristic for C4-type photosynthesis was determined in different organs of two herbaceous plants: Reynoutria japonica Houtt. and Helianthus tuberosus L. The activity of phosphoenolpyruvate carboxylase (PEPC) was usually higher in the roots, some of the stem tissues and petioles in comparison to the leaf blades. The highest activity of malic enzymes (NAD-ME, NADP-ME) and phosphoenolpyruvate carboxykinase (PEPCK) was in the petioles and stem tissues of both plants and the lowest in the leaf blades and the pith of Helianthus tuberosus L. and M. Kocurek, J. Pilarski.
During batch culture of Haslea ostrearia the highest carbon (14C) fixation rate was found in vivo in cells that did not accumulate the blue pigment marennine (green form). This fixation rate decreased concomitantly with the accumulation of marennine. In vitro, no phosphoenolpyruvate carboxylase (PEPC) activity was detected, but nearly equivalent activities of ribulose-1,5-bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxykinase (PEPCK) were found in the green form. However, the activity of RuBPC was lower than that of PEPCK during marennine accumulation. In vitro carboxylase activities were strongly inhibited by the addition of a marennine extract. A full description of this inhibition could not be confirmed within the cells because marennine accumulates in small cytoplasmic vesicles. and G. Tremblin, J.-M. Robert.
Water deficit, when rapidly imposed on three C4 grasses of the different metabolic subtypes, Paspalum dilatatum Poiret (NADP-malic enzyme), Cynodon dactylon (L.) Pers (NAD-malic enzyme) and Zoysia japonica Steudel (phosphoenolpyruvate carboxykinase), caused decreases in photosynthetic rates, in the quantum yield of PS II and photochemical quenching, and in the activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC). The results provide evidence for non-stomatal limitations of photosynthesis differing in nature between the three species. and A. S. Soares-Cordeiro ... [et al.].