Maria Sharapova celebrated her return to the grand slam spotlight with an emphatic 6-3, 6-4 win over Bethanie Mattek-Sands in what was a clash of styles in more way than one at the Australian Open.
The third-seed, wearing a sleek pale blue dress, was made to work hard for her passage into the second round and lost her service twice as her American opponent mixed things up with her all-court game.
Earlier, men's top-seed Rafael Nadal advanced to the second round.
Nadal's Australian opponent Bernard Tomic, bothered from the start by a left leg injury, retired from the match after losing the first set 6-4.
Roger Federer, Andy Murray and defending champion Victoria Azarenka also won amid temperatures that topped 42 Celsius (108 Fahrenheit).
Federer started his record 57th consecutive Grand Slam tournament with a 6-4, 6-4, 6-2 win over Australian wild-card entry James Duckworth on a day when the heat forced at least one player to black out during his match.
Azarenka played the opening match on the center court, and said it felt 'like you're dancing in a frying pan'.
She had a 7-6, 6-2 win over 91st-ranked Johanna Larsson of Sweden.
Wimbledon champion Murray, on the comeback from minor back surgery in September, had a 6-1, 6-1, 6-3 win over Go Soeda of Japan and Juan Martin del Potro rallied for a 6-7, 6-3, 6-4, 6-4 win over US qualifier Rhyne Williams.
Former world number one Lleyton Hewitt lost in five sets to 24 seed Andreas Seppi of Italy only a week after beating Federer in the Brisbane International final.
Whether it's safe or not I don't know, but you've got to be very careful.
A hot, gusty breeze swirled across Melbourne Park all day, making conditions more challenging instead of cooler. The crowd for the day session was 35,571, almost 12,000 down on day one.
Murray agreed the conditions bordered on being dangerous.
"It's easy to say that the conditions are safe ... but it only takes one bad thing to happen and it looks terrible for the sport when people are collapsing,'' Murray said.
"Whether it's safe or not I don't know, but you've got to be very careful.''
Tournament referee Wayne McKewen defended a decision not to invoke measures which would have seen outdoor matches suspended and the roofs on two arenas closed.
Czech veteran Radek Stepanek retired with a sore neck in the fourth set against Blaz Kavcic, but said it was not heat-related.
Jo-Wilfried Tsonga, the 2008 Australian finalist, advanced with Milos Raonic, Kei Nishikori, Grigor Dimitrov and Fernando Verdasco.
American Sloane Stephens, who beat Serena Williams in the quarterfinals here last year, defeated Yaroslava Shvedova 7-6, 6-3 and 2004 US Open champion Svetlana Kuznetsova and 19th seed was beaten 6-3, 6-3 by Elina Svitolina of Ukraine.
Agnieszka Radwanzka, Jelena Jankovic, Caroline Wozniacki, Simona Halep, Carla Suarez Navarro, Dominika Cibulkova and American Christina McHale all advanced.
Wozniacki said the court was scorching in her 6-0, 6-2 win over Lourdes Dominguez Lino, which started at 11 am.