8 Feb. Science 8 Julius von Sachs; “the dilemma of detail” in understanding photosynthesis AND in understanding the history of the discovery of photosynthesis

Continuing with the history of the discovery of photosynthesis. https://www.youtube.com/watch?v=kKMNig0Cz04

We are trying to discover how the claim of photosynthesis was discovered and justified.

6 CO2+ 12 H2O–> light –>C6H12O6 + 6 O2 + 6 H2O

What contributions to the claim came from the work of van Helmont and Ingenhousz?

Today we will look at the work of Julius von Sachs. The narrator says Sachs is as important to biology as Darwin. What ideas does Sachs contribute?

As we discussed earlier, understanding a complex process like photosynthesis brings us face to face with the “dilemma of detail.” Though the video we are watching is one of the only popular treatments of the history of botany, it, too, oversimplifies the actual history. This video leaves out some important steps and scientists, like Senebier and de Saussure and others, who develop the basic claim about plants taking up carbon from carbon dioxide in the atmosphere and releasing oxygen. They also worked on the process of plants using the oxygen during plant respiration. Growth in plants is fueled by the energy that is captured during photosynthesis. Both photosynthesis and respiration involve gases taken in and released by plants.

This is useful: http://photobiology.info/History_Timelines/Hist-Photosyn.html

The narrator of the video, Timothy Walker, spends a good amount of time on Julius von Sachs. Von Sachs is hugely important to the history of botany, true, but his discoveries about the claim of photosynthesis are a part of the puzzle just like those of other scientists. It is interesting to consider why Walker focused on some of the scientists’ discoveries and not others.

While this article is advanced, you can still find it useful for reference: http://www.life.illinois.edu/govindjee/Part3/6_Govindjee_Krogmann.pdf

This exhibit gives some insight into the ways people thought about plants in the 18th century–the period when important pioneer work was done with photosynthesis. https://www.nybg.org/poetic-botany/#start

Consider, too, how many things were coming together in science in these centuries–knowledge of gases, the conservation of mass, patterns of organization with elements, intuitions about atoms and molecules. The scientists involved in this grand enterprise were motivated by many things from deep curiosity to the desire for wealth and fame. The theories scientists started included ideas that were eventually discarded (like phlogiston theory). It is so fascinating that significant discoveries were made with “wrong” theories. Think about how difficult it is to give up an idea that has made sense. Think about the “Lessons from Thin Air” documentary and about your own efforts to learn and understand.

After Sachs, what is left to discover? We’ll work this out with new groups.


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