The Hydration Cell is a tool added by IndustrialCraft 2. It is acquired from placing a Water Cell In an Extractor and then placing the resulting Coolant Cell inside of an extractor to make a Hydration Cell. To use the cell hold the right mouse button while holding it on IC2 Crops that contain plants. For optimal use and to prevent overwatering it is advisable to use a Crop-Matron.
Hydrating and fertilizing IC plants on Crops is important due to the hidden "Nutrition" value that is applied to Crops and may cause a Seed Bag to refuse to plant or vanish instantly back into the player's hand upon planting because of a low nutrition score. Plants failing because of a low nutrition score is not to be confused with an improper light level. Another thing to bear in mind is that hydro-cells do not replace water and a Water source block should be kept nearby.