THE young Greens returned to winning ways with this victory at Langsford Park which put a dent in Pompey's title ambitions.
The visitors also finished the game with nine players as they completely lost their discipline but to be fair they looked a harder side to beat after going a man down.
Argyle started well with Pompey goalkeeper Nick Hall saving well from Alex Battle's 20 yard free kick before Connor McAuley headed Battle's cross wide at the far post. Hall pulled off a great point blank save from Battle before he was finally beaten on 20 minutes.
Ousmon Saidy's crude challenge on Battle gave the Argyle striker the opportunity to convert the penalty himself - which he did.
Saidy made amends when his brilliant tackle robbed Alex Fletcher of a goal before the referee's eagerness to blow the whistle saw Battle's goal ruled out in favour of a free kick for the Greens.
That was forgotten a minute later as Josh Richards swung the ball across for Aaron Taylor to guide a great header across Hall and inside the far post.
Pompey were left with a mountain to climb in the final minute of the half when skipper Eddie Wakley received his second caution and an early shower.
As is very often the case Pompey made a fist of the game after the break with Harvey Bradbury's header cutting the deficit.
Argyle restored their two-goal lead 18 minutes from time when Kyle McDowell made a hash of trying to clear Dan Rooney's cross, and Fletcher reacted in a flash to fire the ball home from eight yards.
Kevin Hodges took the opportunity to make changes but Argyle were given an anxious last couple of minutes after substitute Matt Mayes had fired home from the edge of the box. But their fears were allayed when Bradbury was shown his second yellow and the Pompey threat was extinguished.
Argyle: Michael Cooper, Connor McAuley (Sam Ryan 77), Ryan Law, Callum Rose (Harry Downing 86), Jordan Bentley, Elliott Crawford, Josh Richards, Aaron Taylor, Alex Fletcher (Billy Craske 86), Alex Battle (Luke Jephcott 80), Dan Rooney. Substitute not used: Harry Townsend.