C4 carbon fixation

[The_simpsons]

Something i've been pondering on, are the plants in the family Solanacae (like tobacco, potato, chili, datura etc.) C3 or C4 plants?

[jimmydasaint]

I thought these were C3 but greening potatoes show an alternative mechanism to the Calvin cycle.

 

However, why not read the handbook :

 

http://books.google.co.uk/books?id=0_3XqlcKPpwC&pg=PA368&dq=potato+C3+pathway&ei=TyZBSN6FI4fKjgHyh82IBQ&sig=6xylb0i_5JGxBppu0BXTfQenrVE