I read this novel quite some time ago. It had short stories on genetically altered humans living on different planets.
Sounds like this is James Blish's The Seedling Stars. It has 'seeds' in the name and is a collection of short stories concerning the adaptation of humans to alien environments.
I second PEW's answer and say it sounds a lot like James Blish's The Seedling Stars, which can be considered both a novel and a collection of stories set in the same fictional universe, called the Pantropy series.
The stories, often revised from their first magazine appearances, are "Seedling Program", "The Thing in the Attic", "Surface Tension", and "Watershed".
In the first story Earth is dominated by a tyrannical power which developed from the Port Authority of New York to take over the planet, and a colony on Ganymede, moon of Jupiter, launches seedling ships to colonize planets of other stars by adapting humans to survive in their environments, despite opposition from the tyrannical government.
There are several other stories set on different planets with humans adapted to different environments.
The most famous story is "surface Tension" in which genetically engineered microscopic humans living in a tiny pond on a planet have a sort of a space program equivalent, developing water filled vessels to leave their pond and find other habitable ponds on the surface of their planet.
"Surface Tension" has been in many anthologies and is one of Blish's most famous stories.
I guess this is enough information to show whether "The Seedling Stars" is the the book asked about.