Early ideas about Photosynthesis Flashcards
What did the early Greeks think was the reason plants gain mass?
The early Greeks believe plants gained mass by taking in minerals from the soil.
What experiment did Van Helmont carry out?
He dried out 200lb of earth in a furnace (then moistened it with rainwater) and put it in an earthen vessel. He then placed the stem of a willow tree weighing 5lb in the vessel. After five years, the tree has grown to over 169lb. He again dried the earth in the vessel and found it still weighed 200lb.
What did he notice?
That the amount of soil in the vessel was equal to the amount of soil at the start of the experiment.
From this, what did he conclude?
The tree’s weight gain had come from the water.
What did he miss?
The effect of gases in the air. A large proportion of the mass of the tree comes from the carbon dioxide in the air, which together with water, is turned into carbohydrates through photosynthesis.
What experiment did Joseph Priestly carry out in 1771?
He put a shoot of mint into a closed glass vessel with a lit candle. The candle extinguished very quickly. After 27 days he relit the candle using sunlight focused by a concave mirror. The candle burned again in air that would not previously support combustion.
What did this experiment prove?
That the mint shoot had produced oxygen gas.
