What would happen to the Earths oxygen levels if Giant, G.M plants dominated the entire globe.?

Question

For instance, if they cross-contaminated - with like trees, shrubs, Japanese knot weed, bindweed, bramble and so forth - creating plants that became impossible to bring under control. That grew out of sidewalks, roads and pavements. Taking over human communities, there homes, shops and schools.....What affect would it have on our quality of life.

Answer 1

Nothing at all. The plants have already pushed up oxygen levels as far as they can go hundreds of million years ago, much to the dismay of methanogenic bacteria who have been in hiding ever since.

Answer 2

If oxygen levels go much higher then vegitation will spontaneously combust.

The feedback systems that have kept the oxygen at about 20%, enough to support large land animals but not lead to uncontrolled fires is one of the pieces of evidence for gaia theory by James Lovelock

The possibility of GM superweeds is one of the main arguments against GM, only the agro-chemical companies would profit in a war against nature. http://soilassociation.org/web/sa/saweb....

Answer 3

increase in bio mass of plants can only come from reduction of CO2 quantity in the air and water.

if bio mass increases very much, it will result in colder and drier climate, that will cause reduction in the total quantity of flora.

but if some other ingredient, like a release of large quantities of CO2 from mineral sources occur, the phenomenon you describe could happen, that is vast tropical forests over sizable parts of earth, which are desert now.