Historical Foundation of Plant and Groundwater Interactions - Introduction to Phytoremediation of Contaminated Groundwater - page 5

wrote in his Enquiry into Plants and On the Causes of Plants
about plant-derived poisons. Later, under the Roman ruler
Nero, the Greek physician Dioscorides classified poisons
that included those derived from plants. On the other hand,
the physician Hippocrates wrote that certain plant substances
that today we classify as alkaloids, had beneficial qualities as
long as the dosage was constrained. Therefore, plants have
the potential not only to synthesize powerful chemicals but
to remain unaffected by them. This interaction regarding
plants and natural chemical substances and the analogy it
provides for the phytoremediation of contaminated ground-
water is discussed in Chap. 11.

Pisa, Italy, and became physician to Pope Clement VIII in
1592 (Boorstin 1983).

1.1.3 Johann Baptista van Helmont, Water,
and Plant Growth

The Flemish alchemist and scientist Johann Baptista van
Helmont (1577-1644; Fig. 1.1 ), perhaps most famous for
his first use of the term 'gas' (from the Greek chaos )to
describe matter in an airlike state, continued this search
into the relation between plants and water and composed
perhaps the first laboratory experiment that challenged
Aristotle's Humus Theory. In retrospect, his experiment
seems almost too simple to have been remembered some
300 years later. He placed a 5 lb (pound) (2.2 kg [kilogram])
willow tree in a pot filled with 200 lbs (90.9 kg) of dry soil to
which he added only water. After 5 years (y) the willow
weighed almost 170 lbs (77.2 kg), whereas the soil weight
remained essentially unchanged. He reasoned that plants,

1.1.2 Andrea Cesalpino and Water Absorption

The focus of Aristotle and his students on the interaction
between plants and soil limited the investigation into the
interaction between plants and water . Also, scientists tended
to study what Aristotle had said about a particular subject,
rather than to go out and observe these subjects directly.
Some of the earliest work conducted to understand the
absorption of water by plants did not occur until almost
fifteenth centuries later by the Italian physician and herbalist
Andrea Cesalpino (1519-1603). He concluded that plants
absorb water similar to how a sponge absorbs water, perhaps
because his observations were made before the development
of the microscope. His work was published in 1583 as part of
his treatise Des Plantis libri XVI (Kramer and Boyer 1995).
The importance of Cesalpino's hypothesis on water
uptake by plants was that it was based on the idea of a
physical process rather than simply conjecture. This is an
important distinction because during the time of his studies,
plants were regarded as possessing forces of magnetism and
suction. In fact, mysticism and alchemy were often used to
explain other processes. For example, during the fifteenth
and sixteenth centuries, there was great interest in testing
Aristotle's four-element theory of fire, water, air, and earth.
Many independent discoveries during this time challenged
this concept, such as the observations of comets in the early
1600s. Such observations shook ancient ideas about the
physical world and, by default, the roles of alchemy and
mysticism were put in doubt.
Cesalpino's interest in plants led him and others to col-
lect, dry, and press leaves of various plants so that the leaf
structure could be studied. This practice remains to this day
and such herbaria are found in most colleges or universities
around the world. Today, at least 180 million specimens are
listed in the Index Herbariorum . Cesalpino had other
interests in plants beside water interactions. His observations
of fungi, for example, led him to believe that they did not
produce seeds and were derived directly from decaying
substances. Cesalpino also directed the botanical garden in

Fig. 1.1 Johann Baptista van Helmont added only water to a 5 lb
(2.2 kg) potted willow tree for 5 years and concluded that the plant
increased in weight some 165 lb (75 kg) to a total weight of 170 lb due
to the plant's uptake of water, rather than soil, because the weight of the
soil did not decrease. This simple experiment challenged the prevailing
Humus Theory. The importance of atmospheric gases on plant growth
was not known at this time, so van Helmont's oversight into the
increase in biomass from CO 2 fixation can be forgiven, perhaps more
so than his failure to keep track of the volume of water he added to the
pot over time.