Hi Gowtham,
It seems some CSS property is been overridden by Fiori launchpad so you can try giving some CSS class with !important in your application so that it wont be overridden.
Also as far as I know TreeTable is part of commons library but your application looks from sap.m and gives good look.
The commons library and sap.m library does not match properly while combining.
Can you please share us how you created this tree structure.
With Regards,
Ramesh Shrestha