![]() The bubbles, however, formed only when the experiment was conducted in the presence of sunlight. He submerged willow plants in water and saw that bubbles formed on the surface of the leaves. Several years later, a Dutch scientist named Jan Ingenhousz, having heard of Priestley’s experiments, began to conduct experiments of his own. ![]() Figure 1: Priestley’s experiments suggested leaves “refreshed” the air inside a closed container. This caused him to suspect that the leaves were somehow “refreshing” the air inside the container. He also found that a previously extinguished candle would reignite inside a sealed jar – sometimes days after it had ceased to burn – if mint leaves were present. Priestley, partially credited with the discovery of elemental oxygen, found that when he placed fresh sprigs of mint leaves inside a sealed glass container, a candle would burn longer than if the leaves were not there (Figure 1). Early experiments towards the discovery of photosynthesis It wasn’t until Joseph Priestley’s experiments a century later that scientists began to suspect sunlight as the major contributor to a plant’s growth. In test after test, mass lost by soil, water, and even carbon dioxide didn’t measure up to the mass gained by a growing plant. None of these explanations, however, held up when tested experimentally. Other scientists assumed plants gained their weight and size from carbon dioxide, while others assumed that water alone gave plants their heft. A 17th century Flemish chemist named Jean Baptista van Helmont thought plants “extracted” the bulk of their food from soil (Van Helmont, 1841). ![]() Understanding Scientific Journals and Articlesīefore scientists understood the process of photosynthesis, they were at a loss to explain how plants could grow and increase their mass so dramatically from what appeared to be a steady diet of water.Using Graphs and Visual Data in Science.Scientists and the Scientific Community.Scientific Notation and Order of Magnitude.The Case of the Ivory-billed Woodpecker.Santiago Ramón y Cajal and Camillo Golgi. ![]()
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