Turn on and off MacBook Pro Retina connected to a Thunderbolt Display monitor
You can bring up the power menu by pressing Control-Eject. You can also directly sleep (Command-Option-Eject), shut down (Command-Option-Control-Eject), restart (Command-Control-Eject), or turn off the display (Shift-Control-Eject) using the keyboard. You can also press any key to wake a sleeping mac.

There is no known way of turning on recent Macbooks via keyboard except for the power button.