BLAIR SEITZ / SCIENCE PHOTO LIBRARY BLAIR SEITZ / SCIENCE PHOTO LIBRARY
A worker tending lettuce seedlings in a hydroponic culture greenhouse. Hydroponics is the cultivation of plants without soil. Instead, the roots of the plant are immersed in a trough through which nutrient-rich water trickles. Hydroponics was first proposed in the 1860s, but reached commercial scales in the 1930s, particularly in America.
Model release available. Property release not required.