Dr. Vidaver noted that in everyday life microorganisms are 
readily moved into the sewage system from the microorganisms 
found on the surface of potatoes simply by peeling them and 
disposing the peels in the garbage disposal. 
Dr. Vidaver presented a diagrammatic representation of a hexagon 
to show the many variables of trying to get microorganisms to 
associate with plants. She explained that this is one of the 
most difficult experiments to do. It is dependent upon the 
following: the microorganism itself, the time of the year, the 
stage of the growth cycle a plant is in, whether the host is even 
present in the environment, whether a vector is necessary, the 
environment itself (including temperature and humidity), the 
presence or absence of water, the presence of other organisms 
(both micro and macro), pre-emptive microorganisms, and the 
inoculum load. 
Dr. Vidaver presented slides of field plots showing that 
organisms could be confined on crops in a field environment by a 
combination of simple biologic and fungicidal procedures. It 
would prevent any spread of the organism to surrounding plots of 
the same crop. She then presented slides showing that organisms 
can be confined to rows of plants within the same field plots. 
In the greenhouse, she showed pictorial evidence of contained 
plant viruses on individual plants. She also showed contained 
pathogenic organisms on single leaves of a plant without 
infecting other leaves. 
Dr. Vidaver said the bottom line was that organisms can be 
confined if reasonable precautions and care are taken to avoid 
problems with cross-contamination. Experiments have been taking 
place for many years with the most potent plant pathogens and 
even these can be dealt with and confined. She added that since 
the turn of the century approximately 10 million experiments had 
been performed with plant pathogens in the field and in green- 
houses which is an enormous history on which to base the proposed 
revisions . 
Dr. Fedoroff underlined that the subgroup was working with 
biological bases. The purpose of the proposal is to give 
guidance to both the investigator and the IBCs who are seeking 
guidance on greenhouse containment practices appropriate for use 
with recombinant DNA experiments involving plants. 
Dr. Fedoroff said there were two containment principles which the 
subgroup established: physical containment and biological 
containment. Physical containment is normally thought of as 
being at four levels. In plant experiments, there are only 
closed boxes and open boxes. She said a closed box is just that, 
closed. However, a box could be open to differing degrees by the 
use of screens or other partial openings. Some of the biological 
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