Biochemical components of the photosynthetic CO2 compensation point of higher plants

Photosynthesis in Grass Species Differing in Carbon Dioxide Fixation Pathways

“…P. schenckii exhibited a r of 10 ± 3 1A I-'. The r value for P. schenckii was less than those estimated previously for P. milioides (4,18,20,22 The leaf anatomy of P. maximum (Fig. lA) Sw. 0.20 ± 0.01 6.4 ± 0.7 Panicum rivulare Trin. 0.28 ± 0.03 7.5 ± 1.1 ' Mean and standard deviation of 10 measurements of several crosssections.…”

“…The species which Brown (6) recently assigned to the Grandia group are apparently closely related C3 and C4 species, which may offer the possibility of hybridizing C3 and C4 plants. The discovery of two additional species similar in photosynthetic and anatomical characteristics to those reported for P. milioides (3,4,10,17,18) shows that reduced photorespiration and intermediate photosynthetic characteristics are not limited to one species in this genus. Further studies of species in this group of Panicum species should aid in understanding relationships between C3 and C4 photosynthetic pathways and the possibility of manipulating photosynthetic characteristics to improve efficiency of C3 plants.…”

“…Response of AP2 to 02, CO2 evolution in the light, and r of P. milioides were found to be intermediate to those observed in P. maximum, a C4 species and Festuca arundinacea, a C3 species (4). The intermediate gas exchange characteristics of P. milioides have been confirmed in other laboratories (17,18,20,22). Leaf anatomy of P. milioides ' This research was supported by state and Hatch funds allocated to the Georgia Agricultural Experiment Stations. 2Abbreviations: AP: apparent photosynthesis; F: CO2 compensation concentration; PPFD: photosynthetic photon flux density.…”

“…(C3) and P. miliaceum L. (C4). Reduced photorespiration in P. milioides may be ascribed in large part to slightly elevated activities of P-enolpyruvate carboxylase detected in this species (10,17,18,21) in combination with relatively low activities of ribulose bisP oxygenase (10,18) and glycolate oxidase (21). Recent information suggests that compartmentation of P-enolpyruvate carboxylase and ribulose bisP carboxylase in the mesophyll and bundle sheath cells, respectively, may be an important factor in the reduced photorespiration in P. milioides (23), although no such compartmentation was detected in an earlier study (21).…”

Comparative Growth Analyses of Panicum Species with Differing Rates of Photorespiration

“…Trin., is intermediate between C3 and C4 plants with respect to photorespiration. In contrast to other reports in the literature of C3 species with altered rates of photorespiration (4,12,14,(21)(22)(23), this observation has been independently confirmed in several laboratories based on a variety of CO2 exchange parameters, including reductions in the 02 inhibition of net photosynthesis, the CO2 compensation concentration (F)2, and the rate of CO2 evolution in the light (2,3,8,10,12).Although leaf anatomical studies of P. milioides have revealed some features of Kranz anatomy characteristic of C4 plants (2, 3, 9), biochemical investigations (8)(9)(10)(11)13) indicate that this species has not reduced photorespiration and the associated 02 inhibition of photosynthesis by a C4-like CO2 concentrating mechanism (5). For example, the primary products of photosynthesis in 14CO2-air are 3-P-glycerate and glycerate rather than C4 dicarboxylic acids (8,9,11).…”