Google Nexus 7 displays all notifications on the top left hand corner of the device. These includes notification from Google Plus app such as when some one in your Google Plus Circle mentions your name in a post or add comments etc. But if you do not want to receive notifications from Google Plus or want to choose the kind of notification to be received then you can customize this using the option available as part of Google Plus Settings.
Step 1: Tap the Google Plus app on the device.
Step 2: Tap the menu options and select Settings from the drop down list.
Step 3: Tap the Notifications option in the Settings screen.
Step 4: The Notifications screen will provide option to completely turn off all the notifications. This can be done by changing the Notifications Switch state to OFF.
But if you want to turn off specific notification, for example you do not want to receive any comments notification then un mark check box next to Comments option.