The discovery of The Chloroplast
Julius Von Sachs
&
Theodore Wilhelm Engelmann
By: Jan Villamor
Anna- Maria Allen
Amanda Brennan
Previous Knowledge
• Phototropism
• Plants take in CO₂ and produce O₂
(from the discoveries of F.F Blackman, Van Helmot, and Jan
Ingenhousz)
Julius Von Sachs (1832-1897)
•
•
•
•
A German botanist
Fouder of experimental plant physiology
Discovered that photosynthesis occurred in the chloroplast
Found out that starch is present in chloroplasts by using the
Iodine test
• It is thanks to him that we have the Iodine test that we use
today
• Had a great influence on British and American Botany
Major experiments
• Grew plants in water instead of soil
• As a result, it demonstrated that plants can grow
with just water, the right amount of nutrients and
sunlight
• He used the Iodine test to show that carbon was
first accumulated as starch in the leaves of plants
• Learned that chlorophyll, light and CO₂ are
necessary for carbon fixation - carbon fixation is
the first stage of the dark reaction of
photosynthesis
Theodore Wilhelm Engelmann (1843-1903)
• A German botanist, physiologist, microbiologist, university
professor, and musician
• Showed that the light reactions of photosynthesis is converted
into chemical energy within the choloroplast
• Aim was to discover which part of the cell functioned as light
receptors
Major Experiments
• Used a modified microscope that was able to distinguish and
measure different wavelengths of light
• Measured the different wavelengths of light on photosynthetic
activity
• Conducted an experiment that involved illuminating a filamentous
alga called Spiragoya (a form of green algae commonly found in
freshwater ponds and ditches).
-Light was passed through a prism, exposing all the parts of
the spiragoya in different wavelengths
- aerobic bacteria were used to locate where the alga was
releasing the most oxygen
- the bacteria clumped under the red and blue light
Experiment Findings
• Proved that photosynthesis takes place inside the
chloroplasts of plants
• Photosynthesis is necessary in order for plants to
survive
• Chloroplasts receive the most energy from red
and blue light more than any other colour in the
spectrum. A year later, Engelmann discovered
that purple bacteria used UV light in the same
way
Link:
Basics of the Chloroplast
References:
1) "Julius von Sachs Facts, information, pictures | Encyclopedia.com
articles about Julius von Sachs." Encyclopedia - Online Dictionary |
Encyclopedia.com: Get facts, articles, pictures, video. N.p., n.d. Web. 13
Nov. 2010. <http://www.encyclopedia.com/topic/Julius_von_Sachs.aspx>.
2) Nair, Sonia. "What is Spirogyra." Buzzle Web Portal: Intelligent Life on
the Web. N.p., n.d. Web. 14 Nov. 2010.
<http://www.buzzle.com/articles/what-is-spirogyra.html>.
3) "Theodor Wilhelm Engelmann - Wikipedia, the free encyclopedia."
Wikipedia, the free encyclopedia. N.p., n.d. Web. 14 Nov. 2010.
<http://en.wikipedia.org/wiki/Theodor_Wilhelm_Engelmann>.