Today, I was browsing through the manual and I discovered, Exposure Lock ("*" button on the back), that can be used when taking panoramas.
If the panorama spans dark and bright regions, the camera re-computes the exposure between successive shots which makes the panorama look unevenly lit when it is stitched. Pressing the "*" button locks the exposure setting and keeping it pressed while panning the camera and shooting, ensures the same exposure is maintained across the entire panorama.