AngularJs same directive for multiple Element, how to change a Isolated scope value

Question

Iam using a directive to form a select element, repeating the json and forming select for each element. Now change of first dropdown1 i need to change the allowed_values of dropdown2. My sample Code.

<div ng-repeat="(k,v) in data">
  <dyna-select label=k field=v></dyna-select>
</div>

app.directive('dynaSelect', function() {
  return {
    restrict: 'E',
    template: `<div>
                 <label>{{label}}</label>
                 <select ng-options="items as items for items in field.allowed_values" >
                 </select>
               </div>`,
    scope: {
        field:=?field,
        label:=?label
    }    
  };
});

var data=  {
  "dropdown1": {
    "allowed_values": [
      "option1",
      "option2"
    ]
  },
  "dropdown2": {
    "allowed_values": []
  }
}