By using advanced microscopy tools such as SEM and TEM the pollen structure can be studied up to some extent. Is there any other technique available to study the pollen structure of any crop species?
You can use both EM. It depended on your objective. If you would like to observe the sculpture of pollen you have to use SEM. While the structure of organelles TEM should be suitable choice. You can see some essential techniques in palynology textbook.
A range of options available, its depends on what details you want to get into ranging from Stereo microscope to light microscopy to the higher resolution imaging techniques ( Spinning disk confocal microscopes,
Confocal laser scanning microscope, Multi mode confocal microscope) list goes on... you have to choose whats your matter of interest.