The ability to grow plants in greenhouses is a practical necessity for providing an advanced life support system for humans while inhabiting a permanently manned lunar base. Plants will provide fresh food, oxygen, and clean water for explorers living in lunar bases. The conception of first-generation plants growing in a lunar base anticipates them to play a main role in forming a protosoil of acceptable fertility needed for purposively growing second generation-plants (wheat, rice, etc.) at a low cost. The residues of the first generation-plants could be composted and transformed by microorganisms into a soil-like substrate within a loop of regenerative life support system. To reduce a cost of early missions to the Moon, it would be practical to use a local material such as the lunar regolith for plant growing in lunar greenhouses. The use of microorganisms for plant inoculation to leach nutritional elements from regolith, to alleviate lunar stressful conditions, to decompose both silicate rocks and plant straw needed for a protosoil formation is a key idea in a precursory scenario of growing pioneer plants for a lunar base.