46 Photosynthesis
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 creat VB?Wr?72( ?g&??F?R?.( ?'?f????r6&&??v?F?7V??v?B???ss??RV&?6?VB??2&W7V?G2??W?W&??V?G2W??fVvWF&?W2?F?R??R??F?7??F?W6?2v27&VFVB6??R?V'0??FW"?B6??W2g&??F?Rw&VV?v?&G2?V???r( ?F?&RWBF?vWF?W"'??v?B?( ?gV?f7G3?6??R7V6?W2?b&?&???fR&VV?f?V?BF?w&?rBWF???6??2gB??W"F????R6????7BvF6?F?V?w&?r????&RF?W???&P???V????b??WB???VG2?F?66?fW&?W2????F?7??F?W6?2??Wr??&??7&??vW"?fW&?r??#b??6???b??62???rF?BvRf??B?WB&?WB??F?7??F?W6?3??Wr??&??v?W"`?6?????2??f?'F??r???F?7??F?W6?2Gv?6V?GW&?W2gFW"?G2F?66?fW'???Wr??&???7&??vW"?fW&?r??????vV???W7?????????vV???W7????B??6????v?7B????F???6?&???6&?F??6???????