Emotional centuries from Michael Clarke and Steve Smith lifted Australia to a total of 6-473 when rain again interrupted play on day two of the first Test against India.

Clarke (109no) and Steve Smith (142no) shared an unbeaten 119-run stand on Wednesday, when showers marred all three sessions at Adelaide Oval.

Clarke brought up a 28th Test ton in the second over after tea, empowering Smith to open his shoulders and move to his highest Test score with a handful of well-struck boundaries.

The heavy covers were then called for as the pair walked off to a standing ovation.

The final session has been extended until 6.30pm local time.

Smith was stranded on 98 when an early lunch was taken due to the weather, while Clarke was stuck on the same score when the second session ended prematurely after only 11 balls.

But both men reached triple figures, paying tribute to Phillip Hughes in their own way.

Smith moved over to where the number 408 was painted on the outfield, pointing his bat to the sky.

Clarke, who batted in great pain and with little freedom due to his back injury, had a more muted celebration.

The 33-year-old kissed the crest of his helmet and saluted the crowd.

The pair, both friends of Hughes, hugged after each milestone.

Clarke retired hurt on 60 on Tuesday, when he was sent for scans and received injections following a flare-up of his chronic back injury.

But the skipper donned a back brace and strode onto Adelaide Oval on Wednesday, despite Australia’s team physiotherapist Alex Kountouris admitting the captain was “struggling”.

“Unfortunately it’s quite a significant back injury,” Kountouris said before play.

Clarke was clearly restricted – there was no trademark fancy footwork and he limited his shot selection to minimise twisting at the crease.

The 33-year-old grimaced regularly, but India failed to make the most of overcast conditions after Australia resumed day two at 6-354.

Clarke’s running between the wickets was understandably slow, but he and Smith kept the scoreboard ticking over in the morning session with a handful of sweetly-timed boundaries.

Clarke has three degenerative discs in his lower back and every shot caused a clear pang.

“He’s showing a lot of courage … he’s hurting,” Shane Warne said while calling the game for the Nine Network.

“Some (strokes) are going to hurt a lot more than others, but he’s in a lot of pain.”

The skipper overcame a recurring left hamstring injury to play the rescheduled first Test.

But Kountouris believed his current woes were unrelated to the hamstring issue.

“This is his right lower back. This is his old injury, what he’s had in the past,” he said.