how long can plant last for without oxygen? (power outage)

Hi, I have a small plant in a bubbler right now and a power outage killed the air pump. how long can a plant last for before it dies?

depends on what size rez. you have

basically until all the oxygen in the water is used up. i know they sell temporary aerating stones at pet stores

For long power outages you are best off to drain the res and manually mist the roots with a spray bottle a couple of times an hour with weak nute solution. A manual aeroponic if you will. Just be sure the roots NEVER dry out. Better to over mist than under mist.
EDIT: you can leave an inch or two of the roots submerged if you like. Hempy style. You still have to keep the remaining root structure damp. And be sure to keep your light cycle the same. Haha, just kidding.