Yes, it will, actually.
> The HP stolen by HP-draining moves is increased by 30%. It affects the moves Absorb, Mega Drain, Giga Drain, Leech Seed, Leech Life, Dream Eater, Drain Punch, Horn Leech—and despite not being HP-stealing moves—Ingrain and Aqua Ring. It does not increase the damage dealt by any of these moves.
So the amount of damage dealt is not increased, however the amount of HP you receive from HP draining moves is increased by 30%.
http://bulbapedia.bulbagarden.net/wiki/Big_Root#Big_Root