The document summarizes the history of discoveries about photosynthesis from the 1600s to present. It describes Jan Baptista van Helmont's experiment in 1649 showing that a willow tree's mass gain came from water alone. Later experiments by John Woodward and Joseph Priestley helped establish that plants interact with air. Jan Ingenhousz's experiments in the late 1700s showed that plants produce oxygen through a process involving light. The document then provides details about chloroplasts, photosynthetic pigments, and explains the two-stage light-dependent and light-independent processes of photosynthesis.

1. Ocean County College BIOL 161 Lectures Photosynthesis ... Not like Chinese food, where you eat it and then you feel hungry an hour later. – Ray Liotta BIOL161_08 G. F. Barbato

2. Once upon a time … In 1649, A Belgian physician, Jan Baptista van Helmont, planted a willow sapling in a large bucket with a known amount of soil.

3. After 5 years, the tree had gained 74kg in weight but the soil had lost only 57g.

4. Van Helmont concluded that the tree had made 74kg of new growth from water alone.

5. … long, long ago ... In the late 1600's, John Woodward (at Cambridge University) designed an experiment to test Van Helmont's hypothesis that water was the source of the extra plant mass.

6. In a series of experiments Woodward measured the water consumed by plants. He observed that most of the water was “drawn off and conveyed through the pores of the leaves and exhaled into the atmosphere”.

7. The hypothesis that water is the nutrient used by plants was rejected. Woodward is considered to be the 'father' of contemporary experimental plant physiology!

8. … in a land far, far away ... Joseph Preistly, the British man who is credited with the discovery of oxygen, put a sprig of mint into a transparent closed space with a candle that burned out after combusting all the air.

9. After 27 days, he relit the extinguished candle again and it burned perfectly well in the air that previously would not support it. Priestley relit the candle by focusing sun light with a mirror onto the candle wick So priestly proved that plants somehow change the composition of the air.

10. In 1772, Priestley kept a mouse in a jar of air until it collapsed. He found that a mouse kept with a plant would survive. However, I do not recommend repeating this experiment at home unless you have spare cat.

11. … stuff happened. In 1779, a Dutch physician, Jan Ingenhousz, put a plant and a candle into a transparent closed space. He allowed the system to stand in sunlight for two or three days. This assured that the air inside was pure enough to support a candle flame.

12. But he did not light the candle.

13. Instead, he covered the closed space with a black cloth for several days.

14. When he tried to light the candle it would not light. Ingenhousz concluded that the plant must function like an animal while in the dark. Hypothesizing that the plant must have breathed, fouling the air. In order to purify the air plants need light.

15. In 1796, Ingenhousz suggested that this process of photosynthesis causes carbon dioxide to split into carbon and oxygen, and that the oxygen is released as a gas. ‘ Starch picture’ of Dr Jan Ingen-Housz on a geranium leaf (prepared by William Ruf and Howard Gest). The image of Ingen-Housz consists of photosynthetically-produced starch granules, which were ‘developed’ by staining with I2-KI. An engraving of Ingen-Housz (in Reed 1949) was photographed, and the negative placed in a slide projector. Light passing through the negative was focused on a geranium leaf (depleted of starch by prior incubation in darkness) for about one hour. After extraction of pigments from the leaf with boiling 80% alcohol, the blanched leaf was flooded with I2-KI solution to stain the starch granules. Within minutes, the details of the engraving dramatically appeared on the leaf. The inscription at the bottom refers to Dr Ingen-Housz’s fame as a ‘smallpox inoculator’. The ‘starch picture’ procedure was invented by Hans Molisch in 1914. (fromGest, Photosynthesis Research 53: 65–72, 1997)

16. Chloroplasts make oxygen This is a photo representing Ingenhousz's original experiments that illustrated the production of oxygen by water plants!

17. Photosynthesis Method of converting sun energy into chemical energy usable by cells

18. Autotrophs : self feeders, organisms capable of making their own food Photoautotrophs : use sun energy e.g. plants photosynthesis-makes organic compounds (glucose) from light

19. Chemoautotrophs : use chemical energy e.g. bacteria that use sulfide or methane chemosynthesis-makes organic compounds from chemical energy contained in sulfide or methane

20. Photoautotrophs: Large, multicellular algae http://www.flickr.com/photos/the0phrastus/2596187747/ http://www.flickr.com/photos/the0phrastus/2596187747/ http://successco.typepad.com/photos/uncategorized/2007/11/28/sea_kelp1.jpg

21. Photoautotrophs: Unicellular Algae http://pubs.ext.vt.edu/422/442-886/442-886.html Euglena http://www.biologie.uni-erlangen.de/botanik1/html/eng/fotonm3_eng.htm http://www.blog.thesietch.org/2007/02/23/algae-its-not-just-for-biofuel-anymore/

22. Focus on plants … http://www.geograph.org.uk/photo/1327365 http://www.monteverdeinfo.com/reserve.htm http://aginfo.psu.edu/Psa/fw97/gene.html

23. Leaf anatomy Cuticle Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis Cuticle Stoma (guard cells)

24. Chloroplasts This photograph is an Elodea leaf (x 400). Individual cells are clearly visible. The green structures within the cells are chloroplasts.

25. It ain't easy being green … Plant Cells have Green Chloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).

26. Electromagnetic spectrum: Physical properties of light energy Gamma rays X-rays UV Infrared & Microwaves Radio waves Visible light Wavelength (nm)

27. Photosynthetic pigments in plants

28. Chlorophylls a and b Chlorophyll b Chlorophyll a Chl a has a methyl group Chl b has a carbonyl group -CHO CH 3 Porphyrin ring delocalized e - Phytol tail

29. Chloroplasts absorb light energy and convert it to chemical energy

30. Remember that the color we see is the light REFLECTED by the object – NOT the color absorbed!! Why are leaves green (again)? Light Reflected light Absorbed light Transmitted light Chloroplast