The document summarizes key experiments and discoveries in photosynthesis research from the 1600s to present. Jan van Helmont discovered in 1643 that most of a tree's mass comes from water, not soil. Joseph Priestly showed in 1771 that plants release oxygen. Jan Ingenhousz found in 1779 that plants need sunlight to produce oxygen. Later scientists like Calvin traced the chemical pathway that fixes carbon to form glucose in the Calvin Cycle.

1. Photosynthesis Chapter 8 pp160-175