On his return to the ground where he was dropped as a novice batsman at the end of England’s 5-0 Ashes whitewash four years ago, Root (83) played admirably until he flicked a catch to square-leg in Mitchell Starc’s first over with the second new ball eight minutes before stumps.
It ended a hard-working stand of 133 between the captain and Dawid Malan (55no), which was then undermined when Jonny Bairstow also fell caught-behind to Josh Hazlewood’s last ball of the day in England’s 233-5 after Root had chosen to bat first.
Root’s trademark frailty extended his sequence of 50s without centuries to 16 out of the last 19 occasions in Tests - an aggravating statistic for one of the world’s best batsmen.
England badly needed him to stay put as they seek a consolation victory to restrict the series defeat to 3-1 - having faltered to 95-3, before Root and Malan focused their minds on a flat pitch.
After a rain-delayed start and early lunch, the extended first session was very much a mixed bag for the tourists.
Mark Stoneman and James Vince impressed briefly and then frustrated too, as they have for so much of a flawed campaign.
There was some crisp timing from the opener until he was caught-behind on the back foot off Pat Cummins.
Then Vince repeated the dose, one pull in front of square off Cummins an especially memorable shot only for another of his stylish cameos to be cut abruptly short when he went to cut the same bowler and also edged behind.
Alastair Cook was on the brink of another major milestone, five short of 12,000 career runs after counting successive back-foot fours off the previously miserly Nathan Lyon, when he fell foul of DRS precision to go lbw.
Umpire Joel Wilson did not give Cook out, on the basis the delivery from Josh Hazlewood might easily have pitched outside leg - but Steve Smith reviewed and was rewarded when technology marginally ruled the ball landed in line, rather than umpire’s call.
Two wickets had fallen for seven runs, after a stand of 60, and the onus was on Root to vindicate his own decision at the toss.
He shouldered the responsibility very seriously, to the extent that he and Malan collected only eight runs in the eight overs after tea - including an off-driven four by the captain off an off-colour Starc.
Malan was more circumspect still, and had two scrapes either side of 30 - first in a mix-up over a single, reprieved by faulty fielding from Mitchell Marsh at point and wicketkeeper Tim Paine, then when Smith failed to lay a hand on a half-chance low to his right at slip from an edge off Lyon.
Smith tried to play on his opposite number’s likely insecurities between 50 and 100, the home attack bowling with great discipline and two men back on the hook to pace.
It very nearly paid off when Root mis-cued Cummins on 67 - but unlike in Melbourne last week, the ball landed safely between the two outfielders.
Malan had another escape too, on 39, when Cameron Bancroft’s throw missed the stumps after he advanced to Lyon and hit the ball straight to short-leg.
England needed some fortune then, no doubt, but had done so much right until Root’s telling late mistake and then the wicket of Bairstow. Questions will undoubtedly be asked why a night-watchman was not deployed following the England captain’s dismissal with only a few minutes left of the day’s play.