Nov. 12, 1917 
Greenhouse Fumigation with Hydrocyanic Acid 
33i 
EFFECT ON PERMEABILITY OF THE LEAF 
In the work of the Armstrongs (3) on hormones and anesthetics and 
their effect on permeability in plants, they distinguished between the 
action of hydrogen cyanid and that of the typical anesthetics. The 
latter disturbs the osmotic relations (and hence permeability) and brings 
enzyms and their substrates together more rapidly, while cyanid affects 
the enzyms directly, especially the ones concerned in pigment formation 
(the oxidases). Osterhout (16), using electrical conductivity as a 
measure of permeability, has demonstrated that both anesthetics and 
hydrogen cyanid cause at first a decrease in permeability, followed 
shortly by a rapid in¬ 
crease. This decrease 
is reversible if the an¬ 
esthetic be removed. 
If the anesthesia be 
carried too far, how¬ 
ever, it is followed by 
an increase in perme¬ 
ability which is irre¬ 
versible. The change 
from one to the other 
probably represents 
the death point of the 
cells. When the Arm¬ 
strongs (4) immersed 
leaves of Prunus sp. 
in water, the leaves 
gained slightly in weight, but lost sugar to the solution; if chloroform or 
ether was added to the water, the leaves gained still more in weight. 
When cyanid was used, there was no increase in weight; and the leaves 
lost no sugar to the solution. 
To determine whether fumigation with cyanid affects permeability, and 
in which direction, the work of the Armstrongs was repeated with tomato 
leaves. The leaf blades were cut off, 'washed in distilled water, dried 
between blotting paper, and weighed. They were then immersed about 
two-thirds their length in a measured volume of the solution to be tested 
and allowed to stand the specified time. After drying and weighing, 
they were exposed freely to the air for an hour and weighed a third time. 
After the removal of the leaves, the solutions were tested with Fehling’s 
solution for the approximate amount of reducing sugars lost by the 
leaves under various treatments. The results are exhibited in Table III. 
15753°—17 - 4 
Fig. 9.—Growth curves of three sets of lettuce plants, showing the 
effect of light and severe fumigation with hydrocyanic acid. 
