For many centuries plants were a puzzle. They grew from the soil, and
most people, if they thought about it at all, accepted the ideas of
the Ancient Greek philosopher Aristotle. He thought that plants were
fed by the soil and relied totally on the soil to grow.
The brief timeline here shows some of the main developments in ideas
about photosynthesis which have led to our modern understanding of the
way plants make food.
| 1648 |
Jean Baptiste van Helmont rejects the idea that plants
are fed by the soil. |
| 1679 |
Edmé Mariotte observes that plants are nourished by
the atmosphere through the leaves. |
| 1754 |
Charles Bonnet observes gas
bubbles given off by a leaf underwater which is brightly lit - an
observation still made in school science laboratories today! |
| 1772 |
Joseph Priestley is the
first person to show that plants take in carbon dioxide and release
oxygen. |
| 1779 |
Jan Ingelhousz discovers that only the green parts
of plants release oxygen, and that oxygen is only given off when
the plants are lit. |
| 1782 |
Jean Senebier shows that green plants consume carbon
dioxide and give off oxygen under the influence of sun light. |
| 1818 |
Pierre Joseph Pelletier and Joseph Bienaimé Caventou
name the green pigment in plants chlorophyll. |
| 1837 |
René-Joachim-Henri Dutrochet demonstrates that only
the green parts of plants absorb carbon dioxide, thus transforming
light energy into chemical energy. |
| 1844 |
Hugo von Mohl discovers chloroplasts in plant cells.
|
| 1859 - 62 |
von Sachs and Pfeffer show that starch is a by product
of photosynthesis. |
| 1881 - 2 |
Theodor Wilhelm Engelmann recognises that photosynthesis
takes place inside the chloroplasts. |
| 1893 |
Brown and Morris suggest that glucose is the first
product of photosynthesis. |
| 1905 |
F.F Blackman recognises that different factors which
affect photosynthesis are interrelated and comes up with the idea
of limiting factors. |
| 1918 |
Willstatter and Stoll determine the structure of chlorophyll. |
| 1937 |
Hill shows that oxygen can be produced by chloroplasts
on their own, outside a plant cell. |
| 1948 - 54 |
Melvin Calvin and his team
work out the path of carbon in photosynthesis. They win the 1961
Nobel prize for their work. |
| 1955 |
Many different scientists have added to our knowledge
of photosynthesis since the work of Calvin. They have filled in
details of the pathways, of the different types of chlorophyll and
the interactions between different systems. But all of their work
has involved complex biochemistry which doesn't concern us in school
biology. All of the basic facts about photosynthesis have been known
since 1954. |
Charles Bonnet
