Study
Oxygen produced by isolated chloroplasts
Hill, Robert
Proceedings of the Royal Society B: Biological Sciences, 1939
Chloroplasts were isolated from leaves and illuminated in the presence of an artificial electron acceptor, with carbon dioxide excluded from the system entirely.
- Studied in
- Plantae
- Sample size
- chloroplast suspensions with artificial electron acceptors
Illuminated chloroplasts released oxygen and reduced the artificial acceptor, with no carbon dioxide present and no sugar produced.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Oxygen evolution is a light-driven reaction that can be separated from carbon fixation, and does not require carbon dioxide.
How NatureHQ reads it
This is the experiment that splits photosynthesis in two. Until it, the process was treated as one thing — light plus carbon dioxide plus water gives sugar plus oxygen — and the natural reading was that oxygen came from the carbon dioxide. Take carbon dioxide away entirely and the oxygen still comes, which means it is coming from somewhere else. That points straight at water, and it is why the light reactions and the Calvin cycle are taught as separate stages.
- Uses artificial electron acceptors rather than the plant’s own.
- Isolated chloroplasts are damaged relative to those in a living cell.
- Establishes separability, not the source of the oxygen, which required isotopes.
Taking the carbon dioxide away and getting oxygen anyway
Is photosynthesis one reaction, or more than one? And does making oxygen require carbon dioxide at all?
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: The Royal SocietyPublished by the Royal Society.
doi.org/10.1098/rspb.1939.0017
This reference was resolved automatically against Crossref on 2026-08-11.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-08-10.