You really don't understand the definition of a cycle do you.
Cycling is about the process of growing bacteria. But when the bacteria is already there, no cycling is required. Thus, the tank is already cycled.
All the plants do is mask the slow production of ammonia and other nitrogen based waste.
Read Diana's book and you will understand that plants do not "mask" things. They actually take in the waste products.
This is only possible with a light bioload, and if for some reason you get a spike in ammonia the plants will not be able to react quick enough to take it out. Bacteria don't stop metabolizing these compounds.
Just like filter media surface, plant surface have plenty of bacteria.