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| L: Illinois tick trefoil |
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R: Purple prairie clover
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Legumes
are flowering plants (angiosperms) in the bean family
(Fabaceae) that play a crucial role in transforming
elemental nitrogen into a form that is usable by plants and
animals. Nitrogen is essential for all living organisms. It is a
component of proteins and of DNA. The atmosphere is 78% nitrogen
but most organisms cannot use nitrogen directly from the
atmosphere.
Nodules on the roots of legumes contain bacteria in the genus
Rhizobium that ‘fix’ nitrogen into a form that
other organisms may use directly, or that may convert to nitrate,
the form most plants prefer. Farmers often rotate crops that
deplete the soil of nitrogen with legumes which restore nitrogen to
the soil.
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