"Photosynthetic plants" refers to plants that are able to produce their own food by converting sunlight into energy through a process called photosynthesis. Full definition
Reasoning that, because it fluctuated daily, water vapour was continually recycling itself in and out of the atmosphere, he turned his attention to carbon dioxide, a gas resident for a long time in the atmosphere whose concentration was only (at that time) dramatically changed by major sources such as volcanoes or major drawdowns such as unusual and massive episodes of mineral weathering or the evolution of photosynthetic plants: events that occur on very long, geological timescales. (skepticalscience.com)
In the end it might be easier to just stop pumping CO2 into the air in the first place and let photosynthetic plants handle the rest. (scientificamerican.com)
Plastids have their own genome and are responsible for harvesting energy from light in photosynthetic plants and algae. (sciencedaily.com)