Tracey dominated the backstretch, but was overtaken by Zuzana Hejnova of Czech Republic coming off the final curve. The Jamaican, however, kept her composure and raced down the homestretch to take the victory in 54.88.
Hejnova finished second in 55.54 while Italian Ayomide Folorunso, who finished very strong from lane one, took the last automatic qualifying spot from the heat in 55.78.
American teenage sensation Sydney McLaughlin was left back in 5th, her time 56.32, which was just good enough to get her in as one of the fastest losers.
Russell, who was given a medical exemption to skip the Jamaica Olympic Trials, and proved her fitness just in time, was a confortable qualifier in 56.13.
Russell eased across the line as Joanna Linkkiewicz of Poland took the top spot in 56.07.
In heat 3, Leah Nugent, who disqualified from heat 3 after crossing the in 55.66 behind American Ashley Spencer, 55.12, is now back into the runnings.
Janeil Bellille of Trinidad and Tobago with 56.25 qualified as one of the fastest losers, but Barbadian Tia-Adana Belle, 56.68 didn’t make it.