The online documentation (login required) highlights a number of items that are 'non-exportable' when using Content Porter:
An export cannot export the following items:
- Font definitions
- Protocol Schemas in publishing
- Schemas in publishing
- Target types in publishing
- Publication Targets in publishing
- Page and Component publishing status
- Security settings for Users and Groups
- Permissions for Publications, Folders, and Structure Groups
- Checked-in and checked-out status for Components, Template Building Blocks, Component Templates, Page Templates, Pages, and Schemas
- History list for Components, Template Building Blocks, Component Templates, Page Templates, and Pages
- Approval Status of individual items
As is highlighted in bold, there are a number of security items that are not exported using Content Porter.
If it is just a small number of Groups and Publications, then I suggest that you set these manually in each environment.
For a larger scale, you may want to consider scripting this with Powershell (or similar). Dominic has an excellent blog post on How to set Rights and Permissions using the SDL Tridion core service API which may give you a start.