36 T. L. Lyon anp J. K. WILson 
to show that the solutions were sterile, but the authors state that it 
improbable that the enzymes were produced by bacteria. 
Summarizing the experiments to determine the presence of oxidiziz 
enzymes outside of the growing roots of plants, it may be said that Molise 
Raciborski, and Schreiner and Reed report the finding of these enzym 
and consider them to have been excreted by the roots as a normal co 
dition of their growth. Evidence of the liberation of reducing substane 
is less conclusive, but if oxidizing enzymes are liberated by plant roo 
it is easily conceivable that reducing substances would be also, as boi 
are well known to occur within the plant tissues. 
TESTS FOR REDUCING AND OXIDIZING SUBSTANCES LIBERATED BY 
PLANT ROOTS 
The data already presented show that a comparatively large amou 
of soluble organic matter may be given off by plant roots during tl 
growing period. ‘This organic matter may be derived in part from ro 
caps and root hairs that are sloughed off by plant roots as developme! 
proceeds. The roots or detached cells may give up to the surroundi 
medium certain specific compounds, some of which may be enzymic — 
character. In order to obtain information on this subject a number 
tests were made to detect the presence of certain substances that mid 
influence reduction or oxidation. 
Reducing substances 
A number of reagents that had been proposed for the detection of t, 
presence of reducing substances were used for testing the solutions | 
which maize plants had grown, and at the same time for testing che 
solutions consisting of the nutrient solution made up as it was for t 
growth of the maize plants. In some cases the solutions in which the plar 
had grown were boiled before being tested, but an unboiled portion w 
always tested at the same time. Some of the reagents failed to gi 
a reaction with any of the solutions tested and were discarded. The 
were methylene blue, methyl violet, gentian violet, sodium selenite, a 
sodium tellurite. These failures may mean merely that the conditic 
under which their reactions occur did not obtain altho reducing substan 
may have been present. 
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