Three second half-tries added some gloss to an unconvincing Scotland display as they opened their autumn series with an edgy 43-20 victory over Tonga.

Full-back Glenn Metcalfe, wing Roland Reid - within a minute of coming onfor his debut - and replacement flanker Gordon Simpson all plundered scores to add to James McLaren's first half try.

Stand-off Gordon Ross converted all four and slotted five first-half penalties to finish with a 23-point haul on his debut.

Scotland, as expected, started off brightly; Mower quickly into the action and Ross combining well with John Leslie in midfield.

Leslie sought to stretch the Tongan defence with long passes, and the tactic quickly paid dividends.

Lock Stuart Grimes found himself in space out in the Scottish backline, and when Tongan lock Feleti Fakaongo dived in round the wrong side of the resultant ruck, Ross calmly slotted the penalty in the fourth minute.

Scotland spurned a try-scoring opportunity moments later when Leslie sprinted clear up the right touchline but Ross soon made it 6-0 with his second penalty after Tongan hooker Aleki Lutui dived over the top of a ruck.

But the Pacific Islanders stunned Murrayfield by grabbing the first try of the match in the 13th minute.

Lock Viliami Vaki exposed Scotland's fringe defence by picking up at a ruck 30 metres out, bursting through Jon Petrie's attempted tackle and sprinting clear of Andy Nicol to the line.

Full-back Sateki Tuipulotu was unable to convert, and Ross's third penalty calmed Scottish nerves in the 17th minute.

But Tuipulotu swiftly replied when the Scots were ruled offside on their own 22, his penalty narrowing the deficit to 9-8.

Tonga reduced the deficit to eight points early in the second half when Scotland prop Mattie Stewart blatantly came in from an offside position and Tuipulotu landed his third penalty.

Ross' first miss of the afternoon hardly eased the growing tension around Murrayfield as the expected onslaught failed to arrive.

Instead, when Metcalfe ran into trouble and Tonga forced a turnover on the Scottish 22, the home side again fell offside and Tuipulotu booted his fourth penalty to make it 22-17.

McGeechan sent on abrasive flanker Gordon Simpson for Mower and prop George Graham for Stewart to inject some momentum into his pack, and the move paid instant dividends in the 56th minute.

Simpson drove purposefully into Tongan territory, and Leslie showed his class to weave his way past several would-be tacklers down the left flank.

The Northampton centre expertly drew the last defender before releasing Metcalfe for a relieving second try, Ross adding the conversion to give the Scots some breathing space at 29-17.

Simpson spurned a clear try-scoring opportunity when he opted to cut inside rather than release right wing Jonathan Steel in space, after Metcalfe had skipped through the Tongan defence.

McGeechan sent on Roland Reid for his first cap after 67 minutes, and theSouth African-born flanker-turned-winger celebrated with a try after barely a minute on the field, James McLaren and number eight Jon Petrie combining to send Reid over in the left corner.

Simpson then plunged over from close range for a fourth Scottish try with seven minutes remaining, Ross converting to put a more respectable gloss on the scoreline at 43-17.

But Tonga centre Siua Taumalolo had the last word for the visitors, rewarding their perseverance with a late penalty.