At close of play, Gowtham was batting on 147 while Shreyas Gopal was on 38. Assam was bowled out for 145 in 59.1 overs on the opening day yesterday.
Gowtham, who bagged four wickets yesterday, hammered 10 boundaries and six sixes in his 158-ball knock and was involved in century stands with Stuart Binny and Shreyas Gopal.
Samarth made a well-compiled 123 in 234 balls, studded with 10 boundaries.
Samarth, who was batting on 75 at lunch, reached his century in the post-lunch session, steadied the ship in the company of Mir Kaunain Abbas.
More From This Section
However, the visitors checked Karnataka's progress with wickets of Samarath, Abbas (30) and Chidambaram Gautam (0) in quick time.
K Gowtham, in the company of Stuart Binny, stepped up to frustrate Assam. They added 103 runs for the sixth wicket before Binny was castled by Das soon after tea.
Brief scores: Assam 145 in 59.1 overs (Gokul Sharma 55, K Gowtham 4 for 20, Shreyas Gopal 3 for 43) vs Karnataka 427 for 6 in 115 overs (K Gowtham 147 batting, Ravikumar Samarth 123, Swarupam Purkayastha 3 for 80).