I read this story (probably a novel, but maybe a short story or novella) in the mid-1990s or earlier. I have an uncertain memory that it may have been a sequel or the second story in a series. I also have a vague memory that passing out from g-forces during a space launch was expected, so the story may pre-date manned space flight.
The story was set during the early stages of terraforming Mars. The project involved plants that were genetically engineered to produce a lot of oxygen. The first part of the story involved a fire breaking out in a forest of these oxygen-laden plants and the protagonists being trapped in their habitat in the middle of the forest and having to dig a refuge from the fire using makeshift tools like chair legs.
As a result of the fire, a representative from Earth who was to evaluate the terraforming project, but who was already prejudiced against it, concluded that he had evidence that the project should be cancelled. He returned to Earth to give his report, and the protagonists followed him to plead their case. But they found themselves crippled and wheelchair-bound on Earth after so long living in the lighter gravity of Mars, and the idea that all the early colonists would be similarly crippled added emotional depth to the case they presented.