Ceyda Sungur showered with teargas in Gezi Park as she came from her nearby university office to defend park from diggers

It is a two-minute walk from Ceyda Sungur's second-floor office to Gezi Park, a rare green space in Istanbul's teeming centre. Last Tuesday, Sungur was among a small group of people who made their way to the park to defend it from the diggers that had moved in to flatten it. The bulldozers had begun tearing out chunks the previous day.

What happened next would transform Sungur – an academic at Istanbul's Technical University – into a global symbol of anti-government resistance. She had dashed out from the university's urban planning department in a red summer cotton dress. She wore a simple necklace and carried a white shoulder bag.

When Sungur arrived she found a line of riot police. One of them crouched down and fired pepper spray directly into her face. The jet sent her hair billowing upwards. As she turned, the masked policeman leapt forward and hosed down her back. The unprovoked attack left her and other activists choking and gasping for breath; afterwards Sungur collapsed on a bench.

A Reuters photographer, Osman Orsal, captured the moment, creating an image which in the ensuing days went viral – shared via Facebook, Twitter and other social media. It has sprung up as a cartoon on posters and stickers. In Turkey's third city, Izmir, one of the many scenes of violent protests against prime minister Recep Tayyip Erdogan, it has been transformed into a giant billboard. You can poke your head through the face and pose for pictures.

The photo sums up the protests that have gripped Turkey over the past 10 days, driven by secular, middle-class Turks incensed by Erdogan's neo-Islamist social agenda and abrasive ruling style. But the image also feels universal. It shows one peaceful protester, dressed as if for a summer garden party, standing up for basic human and green values against an arrogant and mighty state.

Sungur is a reluctant figurehead. On Wednesday, she declined to discuss last Tuesday's drama and her sudden fame as the "lady in the red dress". In brief remarks last week to the Turkish media she pointed out that she was a tiny part of a huge grassroots movement. "A lot of people no different from me were out protecting the park, defending their rights, defending democracy," she said. "They also got gassed."

But speaking from her bright university office, in room 204, her colleagues gave an account of what happened. "There were about 50 people in the park when the police first attacked us [last] Monday," Eren Kürkcüoglu, a research assistant, said. "They stormed in again on Tuesday morning. We went in the afternoon. Ceyda and some friends arrived first. We and other friends followed at 3pm.

"We found her lying on a bench after the police attacked her. She was trying to get her contact lenses out."

Dr Aliye Ahu Akgün, an associate professor, and Sungur's friend, who was also gassed at the protests, said the experience was deeply unpleasant. "Your eyes start to burn. You want to cry but you can't. Your lungs hurt. I'm a smoker but it was worse than that."

Ironically, the authorities brutal behaviour acted as a catalyst, as more people flooded into Gezi Park and the adjoining Taksim Square. "The resistance grew more solid. At first there were 10 to 15 tents. Then the number tripled," Kürkcüoglu said.

The protests spread across Turkey. In Istanbul, the police changed tactics: arriving at night and lobbing gas canisters at activists encamped there. Despite her ordeal, Sungur returned to defend the park every day, her friends said; the gas wafting daily into her office a reminder of the encounter, they added.

On Wednesday, the scene around Gezi Park was one of devastation. Immediately in front of Sungur's university building were several trashed and vandalised buses. The road winding down the hill to the Bosphorus was filled with makeshift barricades; anti-Erdogan graffiti covered practically every wall, built by students to try and keep the riot police out. They eventually succeeded. The police abandoned the area earlier this week, with Turkey's deputy prime minister on Tuesday apologising for last week's violence.

The grassy spot where Sungur was gassed is next to a shady alley of elegant plane trees. It is now the hub of a vast, vibrant open-air democracy festival. Dozens of young people have pitched tents; at night crowds pack every available corner; banners proclaim numerous slogans – ecological, socialist, and pro-alcohol. The bulldozers demolished a few trees and a cobbled pedestrian bridge. But remarkably most of the enclave was saved.

Sungur's urban planning department had long wrestled with the theme of how to reconcile Turkey's economic and building boom with the fundamental needs of citizens. A petition which she and other members of the architecture faculty signed says that the rapid changes to Istanbul threaten not only "our professional field but also our living environment". The petition adds: "All these top-down decisions disregarding planning and urban management principles are not approved by Istanbul's citizens. We don't accept them."

Akgün, Sungur's colleague, said: "The park is one of the last surviving green public spaces here. It's calming to walk through it. You feel good." Typically, Erdogan's government had taken an "upside-down" approach to planning, she said, building first and considering the consequences afterwards. Akgün said she respected Sungur's reluctance to become a poster girl for the anti-government protest movement, less of a revolution than a spontaneous citizens' revolt.

Virtually all of Sungur's students have taken part in the protests. Some of them are sitting finals; the dean refused a plea for exams to be postponed. On Wednesday, several of them were tinkering with architectural models in a large room next to her office. Others sat in a shady courtyard below and talked softly.

Akgün admitted: "I've been trying to teach my students for four years about the importance of urban planning. Now they finally understand what we are saying."

• This article was amended on 6 June to correct the spelling of Ceyda Sungur