Photosynthetic/Photorespiratory Carbon Metabolism in the C3-C4 Intermediate Species, Moricandia arvensis and Panicum milioides1

摘要

The distribution of 14C in photosynthetic metabolites of two naturally occurring higher plants with reduced photorespiration, Moricandia arvensis and Panicum milioides, in pulse and pulse-chase 14CO2 incorporation experiments was similar to that for the C3 species, M. foetida and Glycine max. After 6 seconds of 14CO2 incorporation, only about 6% of the total 14C fixed was in malate and aspartate in both M. arvensis and P. milioides. The apparent turnover of the C4 acids was very slow, and malate accumulated during the day in M. arvensis. Thus, C4 acid metabolism by M. arvensis and P. milioides had no significant role in photosynthetic carbon assimilation under the conditions of our experiments (310 microliters CO2 per liter, 21% O2, 1100 or 1900 micromoles photon per square meter per second, 27°C).