ember store is undefined

Here are the main code lines of my ember application :

/** Initialization and configuration */
App = Ember.Application.create({
    LOG_TRANSITIONS: true
});
App.ApplicationStore = DS.Store.extend();
App.ApplicationAdapter = DS.FixtureAdapter.extend();

and :

App.GenerationController = Ember.Controller.extend({
actions: {
    generation: function(){
        var graph = this.store.find('graph', 1);
        [...]
    }
}

When my action is launched, I have this in my console : TypeError: this.store is undefined

Can someone help me to fix it ? And moreover, to understand why the store seems not accessible from a controller ?

Thanks