
The Pilgrims were forced to withstand long spells of pressure from the visitors, with Liv Giles producing a string of important saves to keep Matt Green’s side in the contest.
However, a long-range lob from former Argyle defender Arabella Suttie and Kerry Beattie’s finish gave Portsmouth a two-goal advantage before the break.
Argyle continued to battle after the interval and created moments of their own, but Zoe Barratt’s late double secured all three points for the visitors, leaving the Greens bottom of the table without a point from their first four games.
Portsmouth created the first opportunity of the game but Giles comfortably claimed an early effort before Ellie M Bishop made an important interception to deny the visitors a chance from a dangerous ball into the box.
The home side grew into the game and showed plenty of intent. A good flick-on from Lura Curnock sent Shana Dolbel through towards Hermione Cull, but Portsmouth's former Argyle goalkeeper was able to deal with Dolbel’s attempted chip.
The visitors continued to threaten, though, and Giles was called into action repeatedly. A scramble inside the Argyle box ended with another effort from Portsmouth, while Beattie saw a shot deflected onto the crossbar before Giles claimed the resulting delivery.
Argyle remained competitive and Curnock won a free-kick halfway inside the Portsmouth half. Kiesha Walker took responsibility from the set-piece, but her effort went narrowly wide.
Portsmouth eventually broke the deadlock on 32 minutes. Giles had just produced another excellent stop to deny Barratt from close range, but seconds later Suttie found the net with a lobbed effort from distance to put the visitors ahead.
The advantage was doubled three minutes later. Sofia Mallon fed Beattie on the edge of the box after a mistake from the hosts, allowing the forward to turn before firing into the bottom corner.
Despite further pressure before half-time, Giles and the Argyle defence kept Portsmouth at bay, leaving the Pilgrims two goals behind at the interval.
Argyle made a change at the break, with Ciara Magee replacing Walker. Portsmouth continued to create chances, but the home side showed greater resilience.
A loose clearance almost proved costly when it fell to a Portsmouth player, who fired over, while Giles was again called upon after the visitors worked the ball into the box.
The Pilgrims had their own opportunity on 53 minutes when Dolbel found Chloe Ingrouille, but the forward was beaten by her defender before she could get a shot away.
Brooklyn Brothers was introduced for Kennedy Garside soon afterwards as Argyle dealt with the visitors’ relentless pressure and a succession of corners.
The substitutions appeared to give the Pilgrims a new lease of life, and they began to show more attacking promise. The hosts continued to defend resolutely at the other end, with Giles once again producing an important save before the defence cleared the danger.
The third goal finally arrived on 79 minutes. Substitute Esta Roberts made an immediate impact, with her ball helping create a one-on-one opportunity for Barratt, who calmly slotted past Giles.
Barratt completed her brace in stoppage time, meeting a looping ball towards the back post and firing home to seal a 4-0 victory for Portsmouth.
The Pilgrims now face another difficult test on the road next weekend, travelling to face Oxford United. The hosts will provide a stern challenge, having remained unbeaten and yet to concede in all competitions so far this season.
Argyle will therefore be looking to take the positives from their improved second-half display against Portsmouth into another demanding fixture.
They will then return to Home Park for their final group game of the FAWNL Cup on Sunday, September 27, with Torquay United the visitors.
The fixture will carry an added significance after it was announced that all takings from the game will be donated to former Argyle player and current Torquay defender Roxy Thomas, who is undergoing treatment for a brain tumour.
Thomas joined Torquay after progressing through Argyle's pathway and made her first-team debut for the Pilgrims aged 16.
ARGYLE: Liv Giles, Aliyat Lambe, Ellie M Bishop, Laura Curnock, Shana Dolbel, Kiesha Walker (Ciara Magee h/t), Sienna Gilbert, Kennedy Garside (Brooklyn Brothers 57 mins), Farrah Ambrose, Chloe Ingrouille, Khloe Reed. Substitutes (not used): Saskia Worrall, Phoebe Bettey, Mia Burrows, Lily Coaker.
PORTSMOUTH: Hermione Cull, Jazz Bull, Ava Rowbotham, Kerry Beattie, Jemima Dahou, Sofia Mallon, Amelia Hazard (Esta Roberts 78 mins), Freya Jones (Georgie Freeland 61 mins), Zoe Barratt, Alisha Ware (Summer Hughes 61 mins)), Arabella Suttie. Substitutes (not used): Ella Pettit, Annie Wilding.
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