Rewriting that function would only shave off a line of code:
public function addRow() : void {
var att:TA= new TA();
att.attributeName = "abc";
(template1.dataProvider as ArrayCollection).addItem(att);
I dunno what TA is, but if you wanted it to be even shorter, you could make TA take attributeName in its constructor. Then you could do this:
public function addRow(attributeName:String) : void {
(template1.dataProvider as ArrayCollection).addItem(new TA(attributeName));
}