Use the In
ternet
library to
find out m or a
ore about
the experi
me
one of the nts conducted by
se scientist
s. Then,
write a su
mmary of
the
scientist’s
experime
nts as it
might app
ear in a ne
wspaper
story of th
e time. Giv
e your
story a he
adline.
Understanding Photosynthesis
Joseph Priestley
Many scientists have contributed to understanding how plants carry out photosynthesis.
Early research focused on the overall process.
Later researchers investigated the detailed
chemical pathways.
Using a bell jar, a
candle, and a plant,
Priestley finds that the
plant releases a
substance that keeps
the candle burning—a
substance that we now
know is oxygen.
Peter the Great
becomes czar of Russia
1689
1600
Melvin Calvin
United States
Declaration of
Independence
signed
1771
1643
Jan van Helmont
After careful measurements
of a plant’s water intake
and weight increase,
van Helmont concludes
that trees gain most of
their mass from water.
Mayer proposes that plants
convert light energy into
chemical energy.
1845
1776
1700
1800
1779
Jan Ingenhousz
Ingenhousz finds that
aquatic plants produce
oxygen bubbles in the light
but not in the dark. He
concludes that plants need
sunlight to produce oxygen.
Calvin traces the chemical
path that carbon follows to
form glucose. These lightindependent reactions are
also known as the Calvin cycle.
Julius Robert Mayer
1948
2000
1900
1836
Republic of
Texas formed
after Texans
defeat Mexico
at the Battle
of San Jacinto
1941
Samuel Ruben
Martin Kamen
Ruben and Kamen use
isotopes to determine
that the oxygen liberated
in photosynthesis
comes from water.
1992
Rudolph Marcus
Marcus wins the Nobel Prize
in chemistry for describing
the process by which electrons are transferred from
one molecule to another in
the electron transport chain.