Apr. 5, 1924 
87 
Effect of Modified Hot- Water Treatment on Wheat 
Table VIII .—Effect of the presoak bath or 10-minute bath t or both , on wheat with 
seed coats unbroken or broken during the 10-minute bath or throughout treatment 
Actual and average percentage of 
germination when seed coats were: 
' Variety 
• 
C.I.No. 
Unbroken 
through¬ 
out treat¬ 
ment 
Unbroken 
during pre¬ 
soak bath; 
broken 
during 10- 
minute 
bath 
Broken 
through¬ 
out treat- 
mer t 
Leap. 
4823 
S1.0 
14.0 
0 
Poole. 
3489 
98.0 
34.0 
0 
Power Fife. 
3697 
100.0 
24.0 
0 
Average. 
93.0 
24.0 
0 
Average percentage of increase in weight at end of presoak 
bath. 
23.09 
23.04 
27.65 
Table VIII shows that germination was increased from zero to 24 per cent when 
seed coats were unbroken during the presoak and from 24 to 93 per cent when 
seed coats were unbroken throughout treatment. Unbroken’seed coats, there¬ 
fore, effect protection from injury during both baths of the modified hot-water 
method and particularly during the 10-minute treatment. Table VIII also shows 
that the amount of water absorbed by the seed was greater in the presence of seed 
coats broken during the presoak bath. 
According to Osborne ( 8 ) leucosin is the only one of three proteins in the wheat 
embryo affected by a temperature of 54° C. A solution of leucosin (after a 4 to 
6-hour presoak, the leucosin of the embryo undoubtedly is in solution) becomes 
turbid at 48°., and forms a flocculent coagulum at 55°. The hot water at 54°., 
therefore, through direct contact with the embryo, probably coagulates some 
of the leucosin when the surrounding seed coat is broken, and thus may bring 
about the lethal action previously noted. 
An examination of its physical structure shows how the seed coat may function 
to insulate the embryo. According to Percival (9) and others, the outermost 
membrane of the seed coat over the embryo is the pericarp, and the inner mem¬ 
branes successively are the testa and nucellar layer. It was found that the 
presence or absence of the pericarp did not influence the germination of hand- 
threshed treated seeds. The pericarp was removed 7 from 100 hand-threshed 
kernels of Fulcaster (C. I. 6162). A like number of kernels from the same lot 
with unbroken pericarps were employed. The two lots of seed were subjected to 
the hot-water treatment simultaneously and each was sown in soil in greenhouse 
flats. The resulting germination was 100 per cent for each lot. Hurd ( 5) found 
that the presence or absence of the pericarp also had no influence on the germina¬ 
tion of hand-threshed seeds treated with copper sulphate. The burden of pro¬ 
tection, therefore, falls upon the testa or the nucellar layer, or both. According 
to Percival (9), the crushed cells of these membranes in the ripe seed together form 
a layer six cell-walls thick over the embryo, and it seems not unreasonable that a 
structure of this nature might afford protection to the extent noted during the 
10-minute treatment period. 
Table VIII also shows that some protection was afforded by unbroken seed 
coats during the presoak, and that the rate of water absorption by the seed during 
the presoak was greater when the seed coats were broken. In order to determine 
7 Soaking the seed in water for several minutes causes the pericarp to pucker and loosen, when it may be 
peeled off readily with the aid of a needle or scalpel. 
88285—24-7 
