South Africa were 66 for two at this stage but Kuhn's departure brought De Kock to the crease and his alliance with Amla threatened to take the match away from England before Broad struck with the first delivery after tea.
England captain Joe Root says it was beneficial having predecessor Alastair Cook on the field with him during his first Test as skipper.
The hosts will still feel their aim of backing up their comprehensive first-Test win at Lord's and taking a 2-0 lead in this four-match series is still within their grasp.More news: Garbine Muguruza vs Magdalena Rybarikova: Wimbledon 2017 semi-final preview and prediction
De Kock's 59-ball half-century was a typically fluent and stylish one, but to the first ball after tea he went after Broad - switched to the Radcliffe Road end - and edged to Cook, who was safe if not entirely convincing this time. No visiting side has a won a Test at Trent Bridge after opting to bat first in the last ten years.
He had reason to smile after his two catches, including a very good one down the leg-side to remove South Africa captain Du Plessis off Stokes.
South Africa could nonetheless reflect that they had responded effectively so far to their Lord's setback. A senior player like him is expected to take on more responsibility, especially in the absence of a stalwart like De Villiers.More news: Texas Army veteran's dying wish is to hear from you
Until then runs were not easy to come by, but De Kock, elevated to number four, sparkled with some wonderful strokeplay. I don't think the bowlers hit off stump often enough.
The visitors will need their top four to scrupulously build an innings for them every time they come out for bat, something they failed to do last time.
Where will Day 1 of England vs South Africa 2nd Test match be played?
Philander and Morris swung the momentum back South Africa's way in the last hour, though, with Philander collecting 36 of his 54 runs in boundaries. He got runs himself, and his batsmen and bowlers responded well and triggered a whopping victory for the side. "I took it upon myself to step up in terms of leadership because you do lose a valuable leader in your team, so I thought it was my responsibility to do that", du Plessis said. "We would have chosen to bowl first but they applied themselves well and got stuck in".More news: Man said he killed, burned 4 after drug deals
"I think we did have a lot to prove", said De Kock.
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