A Photosynthetic Timeline
1699 John Woodward
-published his hydroponics( water culture) experiments with mint grown in water of different purity such as rainwater, river water, drainage water, and others.
-found that most of the water that the plant absorbed were expelled through the pores and released to the atmosphere
-concluded that more than water is needed by plants and that soil is responsible for the increase in weight of plants as well
-eliminated the conclusion made by Van Helmont that water was the only factor that contributed to plant growth(Contribution to the History of Photosynthesis: Johann Baptista Van Helmont and John Woodward 25 Nov 2012)
c350BC Aristotle
-proposed that plants, like animals, required food¹
-thought that plants get everything they need from the soil through their roots.
1450 Nicholas of Cusa
-proposed an experiment in which a plant is weighed and then planted in a container containing a weighed amount of soil. After a period of growth, the final weights of plant and soil, as well as the total weight of water applied, are determined and compared to the initial values.
-belief that mass of plant comes from water rather than soil
-was never performed¹
1648 Jan Baptista van Helmont
-performed the experiment proposed by Nicholas of Cusa nearly 200 years earlier
-concluded that the entire mass of the plant came from water, but ignores a very slight decrease in the weight of the soil.
-concluded that a willow tree drew its nutrients, not from the soil, but from water³
1670 Nehemiah Grew
-made careful microscopic studies of the internal structure of plants
-discovered stomata; pondered if stomata allowed exchange of substance between plant and atmosphere¹
