If you have plants, you have bacteria. The more plants you have, the more of any bacteria you have will be in the substrate and vs the filter. The plants actually work to foster bacteria in the substrate by supplying oxygen and even carbon for the bacteria.
There is actually a lot of research out there on this topic. What it boils down to is in heavily planted tanks a good deal of the bacteria is in the substrate. moreover, denitrification should also be fostered as well.
As long as one is willing to plant heavily in the substrate, the bacterial part of things will take care of itself and there is no need to cycle a tank in the traditional sense. However, this should not be interpreted as a lack of nitrifying bacteria in the tank.
Here is an interesting read on this topic, an article by Dr, Hovanec on his site here
http/www.drtimsaquatics.com/resources/library-presentations/aquarium-hobby/aquatic-plants-nitrogen-cycle
If you are a real bug on this stuff, a look at the subsequent research which cites the study referred to in Dr Hovanec's article can be found here
http/scholar.google.com/scholar?q=related:eUjQuhCmWYAJ:scholar.google.com/&hl=en&as_sdt=1,33 (Note, the top article in this link is the article Dr H. cites.) You will read the same sort of thing repeated for different plants and ecosystems.
However, there is another side to this coin. Not all planted tanks are heavily planted. Not all tanks use a lot of rooted plants. Many tanks will need to have more bacteria developed.