- The antidote (1, 8 naphthalic anhydride) is recommended for
corn protection against EPTC injury where the antidote is applied at
a half percent by weight of corn seeds before planting.
conducted to determine the factors affecting the action of antidote in
corn (Zea mays L. var. NB 501D) treated with s-ethyl dipropylthio-
The antidote did not affect germination percentage and germination rate index of corn treated with 0,
2, 4, 6 and 8 ppm of EPTC.
There was slight stimulation of corn germination by EPTC.
Emergence of antidote-treated corn was slow from Bashaw clay
loam, Chehalis sandy loam and Woodburn silty loam soils that were
treated with 0, 3, 6, 9 and 12 lb/A of EPTC.
of corn emergence percentage and rate index values were caused by EPTC at 3, 6 and 9 lb/A rates. Emergence percentage of corn was
88, 91 and 92 percent for clay loam, silty loam, and sandy loam
When the corn root and shoot length was measured six days
after corn germination at 0, 4 and 8 ppm of EPTC it was found that
EPTC increased shoot length whereas antidote reduced it.
was slight reduction in the root length of antidote treated and non-
treated corn seedlings at 8 ppm of EPTC.
When the shoot development of corn was used as a criterion
for antidote action at the 12 lb/A rate of EPTC it was found that antidote was the most effective during the first 48 hours of seedling
Uptake studies with antidote suggested that it is absorbed by
corn seed, shoot and roots. However, the root application of antidote was inhibitory to the first primary root of corn.
When antidote was applied at 40 lb/A rate to the root zone and
soil surface, there was 5 and 12 percent protection, respectively.
The seed application of antidote completely protected corn from
the herbicidal injury of EPTC applied at 12 lb/A rate.
Studies with clay loam, silty loam and sandy loam soils
showed that clay loam retained most of the EPTC applied at 3,
6, 9 and 12 lb/A rate without subsequently injuring corn.
Antidote-treated plants seemed to be more injured by EPTC than the non-treated ones. However, antidote protected corn in sandy loam
and silty loam soils at every level of EPTC.
Low and high light intensities did not affect the action of antidote in corn treated with 0, 3, 6, 9 and 12 lb/A of EPTC.
Antidote did not protect corn from EPTC injury at low temperature
(20 C) at both low and high light intensity (1800 vs. 800 ft-c). On
the contrary antidote-treated plants were injured more than the
non-treated ones at 20 C.
Antidote successfully protected corn from
EPTC injury at high temperature (30 C).
The light intensity was not
a factor affecting the action of antidote in corn.
Applications of antidote at 0,
2, and 4 days indicated that
protection by antidote was not complete after the 2nd day of applica-
Antidote was most protective when applied at 0 and 1 day after
subjecting corn to 12 lb/A rate of EPTC.
When 12 lb/A rate of EPTC was applied to antidote-treated and
non-treated corn at 0,
1, 2, 4 and 8 day intervals it was found that
antidote would protect corn at every application period.
Antidote-treated corn seedlings absorbed more ¹⁴C-EPTC
than non-treated ones. However, antidote-treated corn plants were
also stimulated in metabolizing EPTC. When ¹⁴C-EPTC-treated
corn seedlings were harvested and separated into root, shoot and
seed sections at 1, 3, 6 and 9 day intervals it was found that antidote-treated plants metabolized 12 lb/A rate of EPTC more than the non-treated ones.
It could be assumed that antidote activated the
enzyme system(s) responsible for EPTC breakdown in corn seedlings.
Thin layer chromatography studies showed five to six major
metabolite peaks for 1 and 3-day old corn seedlings treated with ¹⁴C-EPTC. The peaks had the same R[subscript f] values both for antidote-
treated and non-treated plants.
Scanning of the radioactive peaks
also indicated a higher rate of EPTC metabolism in corn seedlings
that were treated with antidote than the non-treated ones.
Studies were also conducted to check the possibility of gibber-
ellic acid involvement as a regulator of the EPTC-metabolizing enzyme system.
Findings indicated that GA₃ alone partially protected
corn from EPTC injury whereas GA₃ along with antidote treatment
significantly increased the corn dry matter production. However,
CCC (cycocel) treatments of corn seeds significantly induced EPTC
injury to corn.