What is the minimum water consumption for Arabidopsis and other plants?
The plant will intake water to keep constant internal water pressure to compensate for evapotranspiration. However, the evapotranspiration will not be a simple universal number.
The evapotranspiration rate strongly depends on temperature, air humidity, water tension inside the plant you want to keep (may it wilt?) and also the radiation received by the plant (PAR - photosynthetically active radiation) and also the air flow. In longer time that will also depend on the ventilation of air in your box. That means how fast water vapour escapes the air from your box and whether any of it condensates.
Also, how much water evaporates from the soil itself? That depends on soil properties, air temperature and also air flow.
A common model for evapotranspiration is by Jarvis and Stewart but is most often used for trees. You can read about interesting measurements of evapotranspiration at Whole plant open chamber to measure gas exchange on herbaceous plants.