With just over two weeks to go before the first Test against New Zealand at Lord's, Root marked himself as the in-form batsman in the country as he pummelled Derbyshire in reaching 236.
The 22-year-old's innings, which included 24 boundaries, followed his match-winning 183 against Durham last week and ensured he will captain the England Lions against the Black Caps next week at full throttle.
Bairstow will also head into Lions duty in fine fettle after he blasted 186 from 193 balls to give Yorkshire an unlikely sniff of victory. The White Rose county reached stumps on 597 for five, and a lead of 122 runs, going into the final day at Headingley.
Elsewhere in Division Two, Graham Napier produced a stunning innings to inspire Essex to an unlikely four-wicket win over Hampshire.
Set 143 to win, after David Masters took five for 41, the hosts collapsed to 31 for six. England skipper Alastair Cook was amongst the batsmen to fail, managing just four, before Napier turned the game on its head with an unbeaten 78 from 88 balls.
James Anderson took three for 28 but Lancashire were deep in trouble after the opening day against Glamorgan at Colwyn Bay.
Lancashire were skittled for 123 and while Anderson made headway he had little assistance as the hosts reached 110 for four.
Gloucestershire recovered from 107 for six thanks to half-centuries from Benny Howell, Will Gidman and Jack Taylor. The trio helped their side to 280 - a lead of 30 - before Gidman struck twice before the close to leave Leicestershire 32 for two.
Australian seamer Trent Copeland took five for 71 as Kent lost seven final-session wickets to be bowled out for 271 against in-form Northamptonshire.
In Division One, Jonathan Trott and Ian Bell both passed half-centuries at Hove in their first competitive hit of the domestic summer.
Trott remained unbeaten on 87 while Bell made 56 as Warwickshire ended the first day on 276 for four against Sussex.
Stuart Broad allayed any injury fears over him as he returned four for 88, but Nottinghamshire were in trouble against Durham.
Broad left the field on the opening two days with a groin problem but bowled freely. England off-spinner Graeme Swann was, however, unable to grab a wicket on his return from elbow surgery to finish with none for 90.
Will Smith's patient 153 helped Durham build a first-innings lead that Nottinghamshire had reduced to six runs, albeit for the loss of five wickets. Michael Lumb was unbeaten on 77.
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