World number one Jankovic muscled her way past Austria´s Yvonne Meusburger 6-1, 6-3 at a sun-baked Melbourne Park while Ivanovic, runner-up here 12 months ago, squeaked past German Julia Goerges 7-5, 6-3 in a less-than-convincing performance.
"I don´t expect myself to step on the court and play perfect tennis from very first moment," Ivanovic told reporters, putting on a brave face.
Djokovic opened his title defense with a 6-2, 6-3, 7-5 win over a spirited Andrea Stoppini.
Swede Bjorn Rehnquist, making his third grand slam appearance, may think twice before attempting to qualify again after the pummeling the 31-year-old received at the hands of a ruthless Roddick.
The American seventh seed, Australian boys´ champion in 2000, four years after Rehnquist had earned that accolade, smashed the Swede 6-0, 6-2, 6-2.
He will next face "the X-Man" Xavier Malisse after the Belgian beat France´s Michael Llodra 7-6, 6-1, 6-1.
Local spirits were lifted by Bernard Tomic who made a spectacular grand slam entrance, becoming the youngest male ever in professional tennis to win a match at the Open. The Gold Coast teenager sent local fans into a frenzy by smashing Potito Starace 7-6, 1-6, 7-6, 7-6.
At 16 years and 89 days old, Tomic is 94 days younger than what fellow Australian Todd Woodbridge was when he beat American John Letts in the opening round at Melbourne Park in 1988.
Czech Republic´s Tomas Berdych, seeded 20th, beat Robby Ginepri 6-4, 6-4, 6-3. Veteran Dominik Hrbaty, who guided Slovakia to a surprise title at the Hopman Cup international mixed team event in Perth earlier this month, beat John Isner in four sets.
Robert Kendrick lost to No. 16 Robin Soderling of Sweden in four sets and Bobby Reynolds went down in straight sets to No. 21 Tommy Robredo of Spain.
Others advancing on the men´s side were No. 8 Juan Martin del Potro of Argentina, No. 11 David Ferrer of Spain, No. 15 Stanislas Wawrinka of Switzerland, 2006 finalist Marcos Baghdatis of Cyprus and 16-year-old Australian Bernard Tomic on his Grand Slam debut.
Women´s No. 7 Vera Zvonareva of Russia posted a 7-6 (7-2), 6-0 win over Slovakia´s Magdalena Rybarikova and No. 15 Alize Cornet of France beat Ukraine´s Mariya Koryttseva 6-3, 6-4. No. 16 Marion Bartoli advanced with a 6-2, 6-4 victory over Britain´s Melanie South.
Former fourth-ranked Kimiko Date Krumm, returning to the main draw of a major after a 13-year hiatus, was beaten 6-4, 4-6, 8-6 by 25th-seeded Kaia Kanepi of Estonia.
The 38-year-old Japanese player, who came out of retirement last year, had won three matches in qualifying.
The first seeded player out of the tournament was No. 23 Agnes Szavay of Hungary, who went down 6-3, 3-6, 6-4 to Kazakhstan´s Galina Voskoboeva.
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