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It’s Brilliant Being Green

On December 8, 1730, Dutch physician and scientist Jan Ingen-Housz was born. A talented, successful, and pro-active doctor who moved to England to learn smallpox inoculation. Ingen-Housz worked on English patients and was so skilled, he was invited to inoculate the Hapsburgs in Austria at their royal request. He achieved fame and recognition but at his core he was a scientist.

He made a series of hundreds of plant experiments in England. Intrigued by plant research he had read about, Ingen-Housz determined to see for himself if he couldn’t just find more than others had. He conducted his series of experiments on green leafy plants grown in water in large jars. Ingen-Housz knew the fundamentals of several sciences so he was very thorough. Plants were big news and scientists were trying to discover every fact of private plant life they could from these taciturn species.

Ingen-Housz made a load of discoveries. He realized a green leaf continued to produce air even when he placed the plant underwater and in sunlight. He managed to remove the water-enclosed plant from the sun’s heat but not from its light and concluded green leaves require sunlight. Without sunlight, the leaves stopped producing the gas bubbles he could see.

In another set of experiments, Ingen-Housz collected the gas and when a smoldering taper was introduced and burst into flame, he realized it was oxygen. In the dark, the leaves stopped producing oxygen but would clean up contaminated or carbonic air (carbon dioxide) that was introduced. His conclusion was that plants converted carbon dioxide into oxygen… that animals converted back into carbonized air.

To Ingen-Housz, leaves were the organs of a plant’s respiration. Each leaf was a natural laboratory for cleansing and purifying the atmosphere. Further, he determined that only the green parts of plants carried out the solar collecting used to grow and to enable the gas exchange.

Although Ingen-Housz did not use the word, he is recognized as the discoverer of the fundamentals of photosynthesis because of the meticulous detail and clarity of his experimental design, his observations, and conclusions. He wrote them all up in a nifty publication called Experiments upon Vegetables, Discovering Their great Power of purifying the Common Air in the Sun-shine, and of Injuring it in the Shade and at Night. To Which is Joined, A new Method of examining the accurate Degree of Salubrity of the Atmosphere. Just in case readers might wonder what the article was about.

Title page of Dr Jan Ingen-Housz' brilliant work on photosynthesis.
Title page of Dr Jan Ingen-Housz’ brilliant work on photosynthesis.

In the ensuing centuries since Ingen-Housz shared his clear and detailed results, others have added to our growing knowledge about plants and their “Their great Power”. Because plant respiration is critical to sustaining life on our planet, scientists continue to investigate the mechanisms of photosynthesis.

B Bondar / Real World Content Advantage