While @DrSheldon's answer points out that a reduced gravity simulator...
...would help you to learn which plants can grow properly in a greenhouse on the moon or Mars.
A access to a long-term reduced artificial gravity field will also yield information on how people might fare on Mars. There is a lot of data on rates of bone loss and deterioration of eyes in microgravity, talk of colonization of Mars makes us wonder about the health effects of living on Mars or even How would travel to Mars without artificial gravity affect a crew's initial experience in Mars gravity?
Experiments exposing astronauts to Mars level of gravity (0.36 of that on Earth) for six months could be compared to ISS data, and let us know if the health effects are two thirds as bad as microgravity, worse, or better.
Hackaday's ISS Artificial Gravity Study Shows Promise for Long Duration Spaceflight links to Off-World Cement Tested for the First Time which explains that there are both advantages and disadvantages to curing concrete in reduced or zero gravity.
Advantages are less or no settling of the aggregate (those bits of rocks, sand, other stuff) to the bottom. Disadvantages are no rising of trapped air bubbles to the top, leaving voids.
Testing these things in a Mars gravity field may be helpful for finding the right mix for Martian concrete, should any be necessary.
For the first time, tricalcium silicate (C3S) and an aqueous solution were mixed and allowed to hydrate in the microgravity environment aboard the International Space Station (ISS). The research hypothesis states that minimizing gravity-driven transport phenomena, such as buoyancy, sedimentation, and thermosolutal convection ensures diffusion-controlled crystal growth and, consequently, lead to unique microstructures. Results from SEM micrographs, image analysis, mercury intrusion porosimetry, thermogravimetry, and x-ray diffraction revealed that the primary differences in μg hydrated C3S paste are increased porosity and a lower aspect ratio of portlandite crystals, likely due to a more uniform phase distribution. Relevant observations led by the presence or absence of gravity, including bleeding effect, density, and crystallography are also presented and discussed.
These images compare cement pastes mixed in space (above) and on the ground (below). The sample from space shows more porosity, or open spaces in the material, which affects concrete strength. Crystals in the Earth sample also are more segregated. Credits: Penn State Materials Characterization Lab