Perhaps this is a quibbling point but the Great Oxidation Event happened more than 2 billion years ago, long before plants evolved. Most atmospheric oxygen was

Perhaps this is a quibbling point but the Great Oxidation Event happened more than 2 billion years ago, long before plants evolved. Most atmospheric oxygen was "created" by cyanobacteria. In fact, plants - along with all other multicellular organisms - were one of the beneficiaries of the GOE as they would not have been able to evolve without it.