title: Effect of varying environments on photosynthetic parameters of C3, C3-C4and C4species of Panicum.
abstract: CO2exchange characteristics and the activity of the carboxylating enzymes phosphoenolpyruvate carboxylase (PEP-C, E.C. 4.1.1.31) and ribulose 1,5-bisphosphate carboxylase (RuBP-C, E.C. 4.1.1.39) during one year in the greenhouse and at two levels of light and temperature in growth chambers were determined in the C3-C4intermediate species P. milioides Nees ex. Trin. These results were compared with those of P. bisulcatum Thumb. (C3) and P. maximum Jacq. (C4). Under all tested conditions, and even when the influence of leaf surface temperature on photosynthetic rates and CO2compensation points were measured, the biochemical and physiological behaviour of the C3-C4intermediate was more similar to that of the C3plant than the C4species. The C4plant P. maximum, however, responded positively, mainly in terms of PEP-C activity and photosynthetic rate, to the regime of high light and temperature. The results presented indicate that in the C3-C4Panicum grown in high light and temperature no direct relationships between a low CO2compesation point and superior growth are evident. It has still to be clarified why in nature a photosynthetic-photorespiratory pathway leading to an intermediate CO2compensation value has evolved in P. milioides.
authors.affiliation: Max-Planck-Institut für Züchtungsforschung, D-5000, Köln 30, Federal Republic of Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Fladung
authors.affiliation: Max-Planck-Institut für Züchtungsforschung, D-5000, Köln 30, Federal Republic of Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Hesselbach
keywords: Environment; Panicum; Photosynthesis