2. By: Alaleh, Atiqa, Anna Lisa

3. Time line J.B. Van Helmont Stephen Hales Joseph Priestley

4. Discovered that water plays an important role in the growth of plants.

5. J.B. Van Helmont performed the willow tree experiment.This experiment was done to determine where the plant got its mass from. In the experiment Helmont measured the mass of the tree and the mass so the soil before and after 5 years. During these 5 years Helmont cared for the plant by watering so it could grow, it was the only outside substance he out in. After the 5 years the tree had grown and so did its mass, the soil however had lost its mass. From this Van Helmont concluded that the willow tree drew its nutrients, not from the soil but from water.

6. Mass of plant Mass of Soil Size of tree After 5 years Mass of plant Mass of Soil Size of tree 2.3 Kg90.7Kgsmall76.7 Kg90.1KgBig

7. Discovered that plants absorb air

8. Hales attempted to show that plants absorb air. He grew a plant in a closed atmosphere. He observed a decrease in the volume of air. He thought that plants absorb substances from the air that caused the volume of the air in the container to decrease. He also concluded that sunlight may have a direct effect on growing plants.

9. Discovered that plants gave out oxygen

11. Candle before plant is added Candle after plant is added Died outKept burning

12. In 1772, Priestley kept a mouse in a closed container until it died. Then he placed a mint plant into a container with another mouse, and it could survive. He concluded that plants restore the air animals breathing, and burning candles removed it. It was then determined that the mouse could survive in the closed container as long as there was a plant in the same container. He assumed that the plant gave off phlogiston (oxygen) which aided the mouse. This experiment showed that the plants produce (phlogiston) oxygen.

13. Mouse before mint plant was addedMouse after mint plant was added DiedStayed alive

14. The Discovery of Photosynthesis." The Orchid Grower: A Juvenile Science Adventure Novel. N.p., n.d. Web. 15 Nov. 2010. <http://www.juliantrubin.com/bigten/photosynthesisexperiments.htmlhtml http ://en.wikipedia.org/wiki/Jan_Baptist_van_Helmont "Stephen Hales and Sunlight." Photobiological Sciences Online. N.p., n.d. Web. 15 Nov. 2010. < http://www.photobiology.info/HistHales.html http://www.photobiology.info/HistHales.html te1.gif. "Index of /family/jbouyer/lessons/Science/askew/mycourses." TexasEducator Home. N.p., n.d. Web. 15 Nov. 2010. < http://www.texaseducator.com/family/family/jbouyer/lessohttp://www.texaseducator.com/family/family/jbouyer/lesso ns/Science/askew/mycourses/botphoto.html> ns/Science/askew/mycourses/botphoto.htm History of Plant Physiology - Biology Encyclopedia - cells, body, function, process, animal, life, hormone, used, structure." Biology Reference. N.p., n.d. Web. 15 Nov. 2010.. http://www.biologyreference.com/Gr-Hi/History- "Stephen Hales." NNDB: Tracking the entire world. N.p., n.d. Web. 15 Nov. 2010. http://www.nndb.com/people/146/000085888/ http://www.nndb.com/people/146/000085888/