A greenhouse will very likely be an essential part of a permanent lunar base. It will complement the life support systems by recycling air, water and producing food. At the same time a greenhouse will have a tremendous psychological effect on the crew, reducing stress and the feeling of isolation from Earth.
A greenhouse module will likely be an expandable structure with integrated support systems. The interaction of all design parameters (like hydroponic vs conventional cultivation, artifical vs natural light, protection from radiation and meteoroids) is a genuinely interdisciplinary challenge.