It is presumed that CO2 movements (into the cell, in and out of the cell), are made under passive diffusion mechanism. That means that CO2 diffuse through membranes, following the decreasing concentration gradients.
From this assessment, the following hypothesis can be written: in photosynthetic cells, the CO2 produced by the respiration in mitochondria can be reused for the photosynthesis in the chloroplasts of the same cell.
In other terms, CO2 produced by the respiration in mitochondria diffuse to the cytosol, where its concentration is lower. Then,CO2 could follow two pathways, 1/ go out from the cell, 2/ enter the chloroplast. In both cases, it would go to a lower concentrated compartment: the external medium, or the chloroplast, where CO2 is fixed by Rubisco.
- Is there any research sapsor contradicting this hypothesis?
you can experiment that idea by marking the CO2 with radioactivity and following it into the cell
For exemple:
The Interaction of Photosynthesis and Respiration and Its Importance for the Determination of 14C‐Discrimination in Photosynthesis
April 2006Physiologia Plantarum 8(4):945 - 953
DOI10.1111/j.1399-3054.1955.tb07790.x
E. Steemann Nielsen