Photosynthesis is the process that drives plant production all across Earth.
It is also the process that produces most of the oxygen that exists in our atmosphere for us to breathe. Plants and the process of photosynthesis are key elements in the critical (for humans and other mammals) planetary oxygen cycle.
When Jan Ingenhousz discovered the process of photosynthesis, he vastly improved our basic understanding of how plants function on this planet and helped science gain a better understanding of two important atmospheric gasses: oxygen and carbon dioxide. Modern plant engineering and crop sciences owe their foundation to Jan Ingenhousz’s discovery.
Jan Ingenhousz was born in Breda in the Netherlands in 1730. He was educated as a physician and settled down to start his medical practice back home in Breda.
In 1774 Joseph Priestley discovered oxygen and experimented with this new, invisible gas. In one of these tests, Priestley inserted a lit candle into a jar of pure oxygen and let it burn until all oxygen had been consumed and the flame went out. Without allowing any new air to enter the jar, Priestley placed mint sprigs floating in a glass of water in the jar to see if the mint would die in this “bad” air. But the mint thrived.
After two months, Priestley placed a mouse in the jar. It also lived, proving that the mint plant had restored oxygen to the jar’s air. But this experiment didn’t always work. Priestley admitted that it was a mystery and then moved on to other studies.
In 1777, Ingenhousz read about Priestley’s experiments and was fascinated. He could focus on nothing else and decided to investigate and explain Priestley’s mystery.
Over the next two years, Ingenhousz conducted 500 experiments trying to account for every variable and every possible contingency. He devised two ways to trap the gas that a plant produced. One was to enclose the plant in a sealed chamber. The other was to submerge the plant.
Ingenhousz used both systems, but found it easier to collect and study the gas collected underwater as tiny bubbles. Every time he collected the gas that a plant gave off, he tested it to see if it would support a flame (have oxygen) or if it would extinguish a flame (be carbon dioxide).
Ingenhousz was amazed at the beauty and symmetry of what he discovered. Humans inhaled oxygen and exhaled carbon dioxide. Plants did just the opposite, sort of. Plants in sunlight absorbed human waste carbon dioxide and produced fresh oxygen for us to breathe. Plants in deep shade or at night (in the dark), however, did just the opposite. They acted like humans, absorbing oxygen and producing carbon dioxide.
After hundreds of tests, Ingenhousz determined that plants produced far more oxygen than they absorbed. Plants immersed in water produced a steady stream of tiny oxygen bubbles when in direct sunlight. Bubble production stopped at night. Plants left for extended periods in the dark gave off a gas that extinguished a flame. When he placed the same plant in direct sunlight, it produced a gas that turned a glowing ember into a burning inferno. The plant again produced oxygen.
Ingenhousz showed that this gas production depended on sunlight. He continued his experiments and showed that plants did not produce new mass (leaf, stem, or twig) by absorbing matter from the ground (as others believed). The ground did not lose mass as a plant grew. Ingenhousz showed that new plant growth must come from sunlight. Plants captured carbon from carbon dioxide in the air and converted it into new plant matter in the presence of sunlight.
Ingenhousz had discovered the process of photosynthesis. He proved that plants created new mass “from the air” by fixing carbon with sunlight. In 1779 he published his results in Experiments Upon Vegetables. The name photosynthesis was created some years later and comes from the Greek words meaning “to be put together by light.”
Some species of bamboo have been found to grow at up to 91 cm (3 ft.) per day. You can almost watch them grow.
