Plants come with nitrifying bactreia on them. There is no suh thing as a planted tank with no nitrifyingf bacteria. One the other habd the are [lenty of tanks with bacteria but mo plants/
Moreover, in plnats that root in the substrate, they will jave roots in anaerobic zones (no oxygen). So there are also none of the nitrifiers/ Some plants transport oxygen down to their roots where they release it. the result is the nitrifying bacteria then colonize. Even more interesting is the fact that denitrifying bacteria will develop in zones above and below this.
Ammonia in water exists in 2 forms, NH3 which is the ammonia gas itself, but in water most of that turns to NH4 which is ammonium. The plants use the ammonium but the bacteria want the ammonia. Even though the plants can consume ammonium faster than the bacteria can consume ammonia, an amount of the bacteria will still be present. It just isn't enough on its own to handle all the ammonia the tank produces.
The biggest different between the plants and the bacteria is that the plants do not make nitrite and thus nitrate either. Only the bacteria do this.
Stability does not caontain any living bacteria, it only contains spores. The nitrifying bacteria in established tanks do not form spores, they reproduce by cellular division when there is more ammonia or nitrite present than they need to thrive.
