(Green) Thumbnail History
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Water, Water
Did you know that most plants are composed of about
90 percent water? It's an essential component of photosynthesis,
necessary for normal cell function, and is the medium
in which nutrients are transported throughout the plant.
Plants need water in different amounts during different
growth stages. A large cucumber plant, when fruiting,
can use up to a gallon of water a day! (Transpiration
uses up the majority of a plant's water intake.) In
hydroponics, water with dissolved nutrients is applied
as a bath, periodically irrigated through the growing
medium, or sometimes sprayed directly on the roots.
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Records
show that plants have been grown without soil for many thousands
of years. The hanging gardens of Babylon used hydroponic techniques.
Marco Polo observed these systems in China. To escape enemies,
the ancient Aztecs reportedly took to the lakes and maintained
large floating rafts woven of rushes and reeds on which they
raised food crops. In 1699 the British scientist John Woodward
grew plants in water to which he added varying amounts of soil.
He concluded that while there are substances found in soil that
promote plant growth, the bulk of the soil is used for support.
By the late 1800s, horticultural scientists were successfully
raising plants in solutions of water and minerals. The modern
science of hydroponics began in the 1930s when Dr. W. E. Gericke
at the University of California raised tomatoes and other crops
on floating rafts, applying the earlier principles in a commercially
successful way. He coined the name
hydroponics as he
worked with water. What more can your students discover
about the history of soilless growing?

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