I looked but couldn't fine the solution.

The booklet with the game said that you can open more plasmid slots by purchasing them at the Gatherer's Gardens stations.

I just got to my first (working) one, and I can't seem to find this option.

Any help?

Yes you cannot buy a slot from the first working gatherer's garden but you will be able to buy one in the next part of the game

Indeed the plasmids slots will become available at the gatherer's garden outside of Fontaine Fisheries in Neptune's Bounty, then I believe Tonic slots will appear at the gatherer's garden after that

quote shadowj

Indeed the plasmids slots will become available at the gatherer's garden outside of Fontaine Fisheries in Neptune's Bounty, then I believe Tonic slots will appear at the gatherer's garden after that

Actually i think the tonic slots appear later because i just made it to the first gatherers garden in Arcadia and i didnt see any

Tonic slots dont start appearing for a while. like after Arcadia.