THE INFLUENCE OF NUTRIENT LEVEL
AND COMBINATION 0N HERBICIDE
UPTAKE AND PHYTOTOXICITY

Thesis for the Degree of Ph. D..
MICHIGAN STATE UNIVERSITY
JERRY D. DOLL
1969

 

5 ha].

 

This is to certify that the

thesis entitled

The Influence of Nutrient Level and Combination
on Herbicide Uptake and Phytotoxicity

presented by

Jerry D. Doll 1

has been accepted towards fulfillment
of the requirements for

Ph.D. degree in Crop Science

(U & SLL/Ww 6“ “oéxflkfi

Major professor Q A l

 

Date May 16, 1969

0-169

 

 

 

 
    
     

amonlc BY I '
«one & sans' 7]
800K BRIBERY INC. 1

LIBRARY BINDERS :r

t .I «lit?

 

n1.§

I ‘l Vliilv .

ABSTRACT

THE INFLUENCE OF NUTRIENT LEVEL AND
COMBINATION ON HERBICIDE UPTAKE
AND PHYTOTOXICITY

BY
Jerry D. Doll

The influence of nutrients and solution pH on her-
bicide absorption and phytotoxicity was studied. The
phytotoxicity of 3-amino-2,S dichlorobenzoic acid (amiben),
2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atra-
zine),'and 3-(3,4-dichlorophenyl)-l-methoxy-l-methylurea
(linuron) in various nutrient combinations and levels was
determined in bioassay experiments. Oats (ézgng sativa L.)
were grown 3 weeks in sand culture with three levels of N,
P and K. Injury ratings and shoot dry weights showed that
only N interacted with the herbicides. Nitrogen, supplied
as nitrate, increased the phytotoxicity of each herbicide.
No interactions with P and K were observed.

Herbicide absorption was measured in nutrient solu-
tions containing different N, P and K concentrations and
14C-labeled amiben, linuron and atrazine. Intact corn,

(Zea maxs L.), soybean (Glzcine max Merr.), and pigweed

Jerry D. Doll.

(Amaranthus retroflexus L.) roots were immersed in treat-

 

ment solutions 4 hr. The effect of N sources and levels
and solution pH on amiben absorption by pigweed and corn
roots was determined. Intact corn coleoptiles were simi—
larly treated to compare uptake in roots with that of
shoots.

The only consistent nutrient effect on herbicide
absorption was a decrease in amiben uptake caused by 10 and
50 mM N03. This means the increased phytotoxicity of ami-
ben, atrazine, and linuron with increasing nitrate levels
observed in the bioassay experiments was not a result of
greater-herbicide absorption.

Only corn root absorption of amiben_varied signi-
ficantly between N sources. More amiben was absorbed in
an NH: solution than was absorbed in N03 solutions, and
these responses interacted with solution pH. Higher pH
values caused highly significant decreases in amiben ab-
sorption by corn and pigweed roots and corn coleOptiles.
Amiben uptake decreased linearly as pH values increased
from 4.0 to 8.0.

Bioassay experiments confirmed amiben was more
phytotoxic to oats grown with either ammonium or nitrate
sources of N, while solution pH had no effect on amiben
phytotoxocity. Therefore, while amiben absorption may vary

with N source and solution pH, these differences are not

Jerry D. Doll

reflected in amiben phytotoxicity. This indicates that
the amiben and nitrogen interaction is not at the site of

uptake.

THE INFLUENCE OF NUTRIENT LEVEL AND
COMBINATION ON HERBICIDE UPTAKE
AND PHYTOTOXICITY

BY

5

0'.
1.
Jerry D? Doll

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY
Department of CrOp Science

1969

5:27;.”00
c]- j (7

ACKNOWLEDGEMENTS

The author wishes to express his sincere apprecia-
tion to Dr. W. F. Meggitt for his guidance and help
throughout this study and for the experience received
through involvement in the weed control project.,

Appreciation is also expressed to Dr. C. M. Harri-
son, Dr. W. M. Adams, Dr. D. Penner, Dr. S. K. Ries and
Dr. A. R. Wolcott for their suggestions and critical re—
view of the manuscript. Special thanks are given to Dr.
D. Penner for guidance received in the laboratory phase of
this study and to Dr. S. K. Ries for use of his laboratory

instruments.

ii

LIST OF TABLES
LIST OF FIGURES
INTRODUCTION
LITERATURE.REVIEW
MATERIALS AND METHODS

RESULTS AND DISCUSSION

TABLE OF

SUMMARY AND CONCLUSIONS

LITERATURE CITED .

APPENDIX

iii

CONTENTS

Page
. . . . . . . . . . iv
. . . . . . . . . . v
. . . . . . . . . . l
. . . . . . . . . . 3
. . . . . . . . . . 15
. . . . . . . . . . 25
. . . . . . . . . . 56
. . . . . . . . . . 59
. . . . . . . . . . 63

LIST OF TABLES

Table Page

1a. ‘Amibenl4-C absorption by corn, soybeans,~
and pigweed roots in 4 hr as influenced
by nitrogen, phosphorus, and potassium
levels in the nutrient solution . . . . . 39

lb. Planned comparisons of amiben and nutrient”
effects and their interactions on amiben
14-C absorption by corn, soybeans and
pigweed roots in nutrient solutions . . . 40

2a. Atrazinel4-C absorption by corn, soybeans,-
and pigweed roots in 4 hr as influenced
by nitrogen, phosphorus, and potassium
levels in the nutrient solution . . . . . 41

2b. Planned comparisons of atrazine and nu-
trient effects and their interactions
on atrazine14-C absorption by corn,
soybean and pigweed roots in nutrient
solutions . . . . . . . . . . . . . . . . 42

3a. Linuron14-C absorption by corn, soybeans,
and pigweed roots in-4 hr as influenced
by nitrogen, phosphorus, and potassium
levels in the nutrient solution . . . . . 44

3b. Planned comparisons of linuron and
nutrient effects and their interactions
on linuron14-C absorption by corn,
sOybean and pigweed roots in nutrient
solutions . . . .i. . . . . . . . . . . . 45

4. Amibenl4-C absorption by corn coleOptiles
in 90 min as influenced by solution pH
and nitrogen source and level . . . . . . 53

5. Effect of pH and ammonium level on the.

phytotoxicity of 8 ppm amiben to oats
grown in sand culture . . . . . . . . . . 55

iv

Figure

I.

II.

IIIa.

IIIb.

IVa.

IVb.

Va.

VIa.

LIST OF FIGURES

Phytotoxicity of amiben to oats grown,
in sand culture 3 weeks in complete
and nutrient deficient solutions . . .

Phytotoxicity of atrazine to oats
grown in sand culture 3 weeks in com-
plete and nutrient deficient
solutions . . . . . .T. . . . . . . .

Interactions of amiben and nitrate on
the injury of oat shoots grown 3 weeks
in sand culture (O=no injury; lO=com-
plete kill) a 'o o o o o o o o o o o o

Interactions of amiben and nitrate on
the dry weight of oat shoots grown
weeks in sand culture . . . . . . . .

Interactions of atrazine and nitrate on
the injury of oat shoots grown 3 weeks
in sand culture . . . . ... . . . . .

Interactions of atrazine and nitrate.on'
the dry weight of oat shoots grown 3
weeks in sand culture . . . . . . . .

Interactions of linuron and nitrate on
the injury of oat shoots grown 3 weeks
in sand culture (0=no injury; lO=com—
plete kill) . . . . . . . . . . . . .

Interactions of linuron and nitrate on
the dry weight‘of oat shoots grown 3
weeks in sand culture . . . . . . . .

Interaction of source and rate of

nitrogen with solution pH on amiben14-C

uptake in 4 hr from nutrient solutions
by corn roots . . . . . . . . . . . .

Page.

26

27

30

30

32

33

36

37

48

Figure Page

VIb. Main effects of pH on amibenl4-C
absorption in 4 hr by corn and pig-
weed roots.from a nutrient
solution . . . . . . . . . . . . . . . . 48

vi

INTRODUCT I ON

The first step in weed control by soil-applied her-
bicides is movement of the chemical from the soil into the
plant. To date, little work has been done on the factors
which control and influence herbicide uptake. However,
there are many investigations and theories concerning inor-
ganic ion uptake (as reviewed by Jennings, 1963; Sutcliffe,
1962; and Fried and Shapiro, 1961). In models proposed by
these authors carriers are involved in transporting inor-
ganic nutrients from the external solution, through the
membrane wall, into the internal solution. It is not known
if similar carrier systems exist for the active absorption
of organic compounds. Competition for sites of uptake oc—
curs between inorganic molecules of similar charge and
size but such competitive effects between.the nutrients and
the organic molecules at the site of uptake have not been
studied. Recently, workers (Dhillon, Byrnes and Merritt,
1967; Hogue, 1968; Nashed and Ilnicki, 1968) have studied
the influence of herbicides on nutrient uptake and accumue
lation by plants, but little or no work has been done to
study the influence of nutrients on herbicide uptake and

phytotoxicity.

From a practical point of view, as the quantity of
both the macro- and micro-nutrients applied to the soil
continues to increase, it might become necessary to alter
herbicide recommendations‘if herbicide phytotoxicity inter-
acts with the nutrient status. One means of determining
the effect of nutrients on phytotoxicity is to measure the
quantity of herbicide absorbed. Herbicides and nutrients
may interact at this site or within the plant.

The soil pH may also influence herbicide uptake
and.phytotoxicity by affecting the ability of the roots to
absorb the chemical or by altering the character of the.
herbicide molecule. Knowledge of pH effects on the uptake
of herbicides cOuld help explain differential herbicide
performance and crop tolerance in the field.'

There is such a divergence of data and Opinion on
herbicide absorption that it is difficult to construct
ratiOnal hypotheses concerning the effect of differences
in the nutrient status on herbicide absorption and phyto-
téxicity. The objectives of this research were: (1) to
study the influence of the nutrient level and combination
on herbicide phytotoxicity, (2) to study root absorption
of herbicides from various nutrient solutions, and (3) to
study the effect_of the hydrogen ion concentration on

herbicide uptake.

LITERATURE REVIEW

The first report of herbicide uptake and nutrient
interaction was by Crafts in 1939. He studied the effects
of varying levels of Hoagland's nutrient solution on the
toxic effects of borax, arsenate, and chlorate. Chlorate
was less injurious to oats as the strength of the nutrient
solution increased while borax and arsenate phytotoxicity
were not affected. Further studies revealed that plants
grown in a high level of nitrate absorbed little chlorate
but cations apparently did not affect chlorate toxicity.
This interaction is simply competitive uptake by two inor-
ganic anions and under low nitrate levels the plant takes
up more chlorate. This apparent competitive uptake was not
reported by Fried and Shapiro (1961).

I The early work which studied the interactions of
organic herbicides and nutrients was with 2,4-dichlorophen-.
oxyacetic acid (2,4-D) and its effects upon nutrient uptake
and accumulation., Loustalot, Morris, Garcia and Pagan
(1963) reported an increase in organic phosphorus in white
bean (Phaseolus vulgaris L.) treated with 2,4-D.> In con-
trast, Fang and Butts (1954) observed a significant de-

crease in the phosphorus content of treated white bean

leaves. Similar decreases were not present in-the root
and stem tissue. Supporting this work, Rebstock, Hamner
and Sell (1954) also noted a decrease in the total phos-
phorus content in the leaves of 2,4-D treated a. vulgaris
plants with no difference in the phosphorus content of the
roots.

Wort (1962) noted the phosphorus content in tomato

(Lycgpersicon esculentum Mill.) was unaffected, increased

 

in white beans, and decreased in soybeans (Glycine max
(L.) Merr.) following an aerial application of-2,4-D.
Thus the interaction effects of 2,4-D and the inorganic
nutrients are complex and vary with species, concentration,
time after treatment, and portion of the plant analyzed.
Alpha,alpha,alpha-trifluoro-2,6-dinitro-N,N-di-
propyl—p-toluidine (trifluralin) altered the region of
phosphorus absorption by cotton and soybeans (Sabbe, 1967).
Trifluralin placed in any of three soil zones, 0-5, 0-10,
or 10-15'cm, shifted the zone of maximum phosphorus uptake.
For example, cotton normally absorbs phosphorus in the 5-10
cm soil zone, but the application of trifluralin at 0.84
kg/ha in this region shifted the site of maximum uptake to
the 0-5 and 10-15 cm zones. Further work by Oliver and
Frans (1968) suggests that the decrease in phosphorus ab-
sorption in the treated region is due to the inhibition of
lateral root development by trifluralin for both cotton

and soybeans. Therefore, it is not a response due to a

herbicide and nutrient interaction in the-soil or at the
site of uptake but rather a morphological effect of the
herbicide on root development.

Using g. vulgaris, Cooke (1957) measured the
changes.in concentration of potassium, chlorine, calcium,
and sulfur at various times after 2,4-D applications. Po-
tassium was found to increase after 8 hr but it had dee
creased after 24 hr. Chlorine followed the same trend at
12 and 48 hr after treatment, while the calcium content re-
mained higher throughout the 48 hr period. The sulfur con-
tent increased slightly after 3 hr but was reduced after 24
hr. Cooke concludes these changes are secondary and prob-
ably are in response to the known increase in respiration
which is then followed by a respiration decrease after a
2,4-D treatment.

One of the first reports of a nutrient and herbi-
cide interaction by a chemical other than a phenoxyacetate
compound was by Bingham and Upchurch (1959). Cotton and

Italian ryegrass (Lolium multiflorum Lam.) were grown in

 

solutions of 3-(3,4-dichloropheny1)-1,l-dimethy1urea (di-
uron)ix1combination with several nutrient levels. They
observed a highly significant interaction between phos-
phorus and diuron such that 2 ppm diuron reduced the fresh
weight of cotton from 84% to 3% as the phosphorus level of
a sandy loam soil increased. There was no similar inter-

action in a silty clay loam soil. For ryegrass the

interaction between phosphorus and diuron was highly sig-
nificant in the sandy loam but not for the silty clay loam.
Thus there is also an interaction between soil type, phos-
phorus level and herbicide. Soil nitrogen, potassium and
pH levels had little influence on the effect of diuron on
p1ant_growth.

In a subsequent study, Upchurch, Ledbetter and
Selman (1963) examined the relationship of soil phosphorus
to the toxicity of twelve herbicides. No phosphorus and
diuron interaction was observed. Of the twelve herbicides,
only 3-amino-l,2,4-triazole (amitrole) interacted with
phosphorus.‘ At the zero P205 leveL.8 ppm amitrole caused
essentially no reduction in the dry weight of cotton in
greenhouse conditions; whereas at the 160 mg P205/100 gm
oven-dried soil level-an 80% reduction in cotton growth
was obtained from the same rate of amitrole. Similar in-
teractions were observed in the field. Thus amitrole was.
apparently more phytotOxic-at-high phosphorus levels. The
authors point out that possibly phosphorus was more phyto-
toxic in the presence of amitrole.

Vega (1964) also reported that there is an optimum
phOsphorus concentration for the enhancement of amitrole
phytotoxicity.g He found that phosphorus enhanced the up-
take and/or translocation of-amitroler14C and explained

this by proposing that amitrole and phosphorus form a

complex. He does not state if the complex is within or
external to the plant roots.

Ries, Larson and Kenworthy (1963) reported peach
trees treated with 2-chloro-4,6-bis(ethylamino)-s-triazine
(simazine) and 3-amino-l,2,4-triazole plus ammonium thio-
cyanate (amitrole—T) had higher leaf nitrogen than where
weeds were controlled by hand hoeing or plastic mulch.
Simazine and amitrole-T influenced the nitrogen metabolism
of apple trees also by increasing the total nitrogen. In:
1965, Ries and Gast found simazine increased the nitrogen of

corn (Zea mays L.» especially when grown at low nitrogen levels.

 

The source of nutrients also affects herbicide up-
take and translocation. Recently, McReynolds and Tweedy
(1969) observed that twice as much simazine-14C was trans-
located to the shoots of corn, rye (Secale cereale L.), and
soybeans grown in nitrate than in ammonium nitrogen.

An interaction between phosphorus and simazine
has been reported by Adams (1964 and 1965).‘ However, using
eight soils, three plant species, three rates of simazine,
and five phosphorus levels, only on two soil types was-
simazine significantly (10% level) more phytotoxic to soy-
beans. Adams concluded that-the effect observed was a
result of simazine decreasing the quantity of phosphorus
required to produce salt toxicity to p1ants..

Dhillon, Byrnes and Merritt (1967) studied the ef-

fect of simazine on the uptake of 32P by red pine seedlings

(Pings resinosa Ait.). The results showed that simazine

at levels of 5 and 10 ppm stimulated 32F uptake, but in-
hibited uptake at higher levels of 15 and 20 ppm. In con-
trast to uptake, the rate of phosphorus translocation from
roots to stems and needles appeared to be stimulated by

all concentrations of simazine between 5 and 20 ppm. They
postulate that the interaction of simazine and phosphorus
at low concentrations may result in growth promotion while
at high concentrations depression and injury. No-determin-
ation of the simazine uptake at different phosphorus levels
was made.

Recently the effect of 3-(3,4-dichlor0pheny1)-l-
methoxy-l-methyl urea (linuron) upon ion uptake by several
species has been reported. Hogue (1968) applied sublethal
and lethal doses of linuron to tomato and parsnip (Pastinaca
sativa L.) foliage and determined its effect upon 32P and
45Ca uptake after 48 hr. Both levels of linuron stimulated
32P uptake and translocation to the leaves in both species..
The increase was in the inorganic phosphorus content.
Linuron inhibited uptake and translocation of 45Ca in both

45Ca uptake inhibition

plants. Hogue concluded that the
and 32F uptake stimulation point to different uptake meche
anisms for anions and cations but no explanation for either
effect is proposed.

The effect of linuron on ion uptake in corn,

soybeans, and large crabgrass (Digitaria sanguinalis

(L.) Sc0p.) was investigated by Nashed and Ilnicki.
(1960). Linuron was applied in the nutrient solu-

tion and 7 days later-the quantities of Ca, K, Mg, P04,
N03, and 804 were determined. Linuron caused marked in-
creases in the Ca and $04 content of the three species and
also increased the N03 and P04 content of soybeans and the
Mg content of crabgrass. The researchers noted that the
increase in nutrient ions after the application of a
photosynthesis inhibitor at lethal levels was unexpected.
Substrates for all biochemical reactions including those.
involving active ion uptake would be reduced when photo-
synthesis was interrupted. They suggested that linuron
affects the respiration which in turn caused an increase
in ion absorption.

Rumburg, Engel, and Meggitt (1960) cite another
example of competitive uptake between two inorganic anions._
Phosphorus at high levels (62 ppm) completely prevented
the expression of arsenate toxicity to oats, and the up-
take of arsenate was 7.5 times greater at 1 ppm phosphorus
in the nutrient solution than at 62 ppm. They concluded
that phOSphorus concentration was of major importance in
relation to arsenate uptake and injury in grasses.

In 1964, Crafts stated that herbicides are taken
up actively according to-the scheme of Broyer (1956). In
this scheme, a carrier system moved the substrate from the

external solution to the internal cell solution. However,

 

10

Hartly, also in 1964, postulated that plants have not
adapted to the uptake of herbicides, but that these "for-
eign" substances are expected to enter by passive diffu-
sion. He_argues that since many herbicides have a somewhat
oil soluble form (e.g. 2,4-D acid but not the anion), they
could penetrate into the suberized waxy tissues easier
than dissolved salts could.

Donaldson (1967) measured and compared the absorp-
tion process of 2,4-D and monuron. Since 2,4-D required

energy and was partially exchanged its uptake was concluded

 

to be active. Monuron, on the other hand, could easily be
exchanged after uptake and required no energy to be ab-
sorbed, indicating its uptake was passive.

Thus there are several different theories as to
whether herbicide uptake is active or passive. Most work-
ers studying herbicide uptake do not discuss their results
in terms of the classical active and passive absorption
mechanisms.

In a recent report, Pardee (1968) identified the-
"carriers" of nearly all transport models as membrane pro-
teins. The processes of binding, translocatibn, and re-
leasing the molecule being absorbed are all performed by
proteins associated with or part of the cell membrane. He
cited the active uptake by protein carriers of phosphoenol-
pyruvate, galactose, and B-galactosides. The molecular

weights and sizes of such compounds are equivalent to those

ll

of many herbicides. Thus it seems possible from the struc-
tural considerations of uptake that herbicides too could
be actively accumulated by membrane protein.

In his recent book, Stein (1967) states that the
flow of one substrate can stimulate flow of another in the
opposite direction. An increase in the nutrient concen-
tration of the culture solution increased the initial rate
of nutrient uptake.*

Recently, site of herbicide uptake studies have

given valuable information concerning the mode of herbicide

 

entry into plants. Knake, Appleby and Furtick (1967) re-
ported that the shoot uptake of soil applied amiben by green
foxtail (Setaria viridis (L.) Beauv.) was similar to the up—
take.of five other preemergence herbicides tested. Appli—
cations which caused a growth reduction of 50% for the

tops of green foxtail caused no growth reduction when ap-_
plied to the root zone. They conclude shoot uptake is the
pathway which resulted in the lethal action of herbicides

to green foxtail. The unpredictability of herbicide per-
formance is illustrated by the fact that Knake and Wax
(1968) discovered that amiben was absorbed differently by
giant foxtail (Setaria faberii Herrm.) application of amiben
at 1.5 ppm in the root zone reduced the dry weight of the
top growth 50% while application to the shoot zone reduced
it 27%. This response was different than that of the other

herbicides. Placement of ten other chemicals in the shoot'

12

zone proved more phytotoxic than placement of the same
concentration in the root zone.

A factor that has pronounced effects on nutrient
ion availability and adsorption in the soil is the pH of
the soil or growing media. Not much is known about the»
soilan effects on herbicide-phytotoxicity. In a synthetic
soil media, Weber, et.al. (1968) observed that the weakly.
basic 2,4-bis(isoprOpylamino)-6-methylthio-s—triazine
(prometryne) was more phytotoxic to wheat (Triticum

aestivum L. em. Thell.) as pH increased. They concluded

 

that the reduction in phytotoxicity at the lower pH was
due to the adsorption of protonated prometryne by the clay
colloid which reduced its concentration in the solution
phase of the growing media.

Corbin and Upchurch (1967) studied the influence,
of pH on the detoxification of soil applied herbicides and
found highly significant effects. They state that not
only can performance of soil-applied herbicides be easily
influenced by the regulation of the detoxification rate by
soil pH, but that this is only one way in which pH can
influence field performance.

In an inclusive study of many soil and climatic
factors which affect herbicidal activity, Upchurch, Selman,
Mason and Kamprath (1966) correlated the soil pH to herbi-
cide performance. There was no or poor correlation of pH

effects on the performance of both N,N-diallyl-Z-chloro-

13

acetamide (CDAA) and 2-chlorally1 diethyldithiocarbamate
(CDEC) at 17 locations for 3 years. Phytotoxicity of
simazine, diuron, and isopropyl N-(3-chloropheny1)carbamate
(CIPC) to cotton and soybeans was generally negatively cor-
related to soil pH. For crabgrass there was no correlation
between phytotoxicity and soil pH.

Contrary to these findings, Nash (1968) measured a
significant increase in the amount of diuron in cat shoots
grown for two weeks in sandy loam as the soil pH increased.

The roots had equal quantities of diuron-14C in oats grown

 

in soils with pH's 4.7, 6.4 and 7.9.- The pH changes had
no measurable effects on oat shoot growth while root growth
increased as pH increased.

Rains, Schmid and Epstein (1964) theorized that a
low pH of the external solution might affect the ion car-
riers of the root such that the rate_of cation absorption
would be reduced due to competition between hydrogen ions
and the substrate cation for available carrier sites. Sim-
ilarly, at high pH values hydroxyl or bicarbonate ions
might compete with substrate anions, thereby reducing the
rate of anion absorption. They also discuss possible dam-
age by hydrogen ions to the ion absorption mechanisms. By
measuring rubidium-86 (86Rb) absorption in a 10 min period,
they found competition with the hydrogen ions for carrier
sites. At pH 3.9 the rate of 86Rb absorption decreased

with time in the absence of calcium, whereas with 0.50 mM

14

Ca it remained constant. Further study revealed that cal-
cium was completely able to prevent hydrogen ion injury to
the carrier mechanism.

In 1958, Fried and Noggle observed that hydrogen
ions not only compete for rubidium carrier sites but also
for potassium, sodium and strontium sites. They further
noted that when the cation concentration was appreciably
higher than the hydrogen ion concentration there was little
or no pH effect due to competition. However when the ion
concentrations were similar, marked pH effects occurred.

No hydrogen ion injury was shown.

MATERIALS AND METHODS

Preliminary experiments were performed to estab-
lish herbicide concentrations which would.reduce the top
growth of oats by 50% (hereafter called the GRSO value).
The effects of the absence of nitrogen (N), phosphorus (P),
and potassium (K) when compared to a complete nutrient so-
lution on plant growth in the presence of a herbicide were
also determined.

Oats (53233 sativa L.) 'Clintland 64' were grown
for 3 weeks in sand culture in the greenhouse as a bioassay
plant in different nutrient and herbicide solutions. Fif-
teen seeds were planted 1 cm deep in nonacid washed # 7
graded quartz sand in a 6 oz styrofoam cup with drainage
holes punched in the bottom. This cup was placed inside a
10 oz waxed cold cup which contained 120 ml of the treats
ment solution. In this manner the oats in the styrofoam
cup were subirrigated by the solution in the waxed cup.

The oats were thinned to 10 plants per cup after emergence.
The daily addition of water maintained the solutions at
their original volume but not at the initial nutrient lev-
e1. The greenhouse temperature was approximately 23 C

and the-day-length was extended to 14 hr with overhead

15

16

flourescent lights. The four nutrient treatments were
complete Hoagland's # 1 solution, Hoagland's minus N,
Hoagland's minus P, and Hoagland's minus K. All solutions
contained the other essential elements and were adjusted
to pH 6.0 with 0.114NaOH. Herbicide treatments were 0, 4,
8, or 16 ppm (w/v) formulated atrazine or amiben in com-
bination with the nutrient solutions. The treatments were
replicated three times in a completely randomized design.
Visual injury symptoms.on a 0 to 10 scale (0 = no injury,
10 = complete kill) and dry weights of the tops were taken
3 weeks after planting. The effect of the absence of one
element from the solution was determined by dividing the
dry weight of the 10 oat shoots by that produced by the
same nutrient treatment without the herbicide.

A factorial experiment with three levels of N, P,
K and a herbicide was designed to study further the results
of the preliminary test. Clintland 64 oats were seeded and
grown in the manner described previously. Treatments were
three levels of N, P, and K (0, one-half, and full-strength
Hoagland's) in all combinations with either 0, 4, or 8 ppm
(w/v) amiben or 0, l or 2 ppm (w/v) atrazine or linuron.
This 34 factorial gives 81 treatment combinations for each
herbicide and the experimental design was a randomized
block with two replications. Plant injury ratings, dry
weights of the tops, and solution pH values were determined

after 3 weeks growth.

17

Previous bioassay experiments were performed with
a nitrate source of nitrogen (N03). In a final study
the phytotoxicity_of.a herbicide with an ammonium source'
of nitrogen (NHI) was compared to the phytotoxicity in
N05 solutions. Simultaneously, the effect of the nu-
trient solution pH on herbicide phytotoxicity was measured.
In a factorial arrangement five pH values (4.0 to 8.0) were
combined with nitrogen levels of 0, 10 and 50 mM NO} or
NH: in two replications in a randomized complete block
design.

To inhibit bacterial growth in the solutions, 20
ppm (w/v) streptomycin sulfate were added to all treatment
solutions. The conversion of nitrate to ammonium in the
N05 solutions was prevented by adding N-serve at the
rate of 0.1 ml/mM NOS per liter of solution. Amiben was
the only herbicide tested and the rates were 0 and 8 ppm.
Fifteen oat seeds were planted as in the previous bioassay
experiment. These were thinned to 10 plants per cup after
emergence. Water, adjusted to the proper pH, was added
daily to bring the solutions to their original volumes.
Injury ratings and dry weights of the shoots were taken.
after 3 weeks growth. Solution pH values were also taken
at the termination of the study. Planned comparisons were
made on the injury ratings and the percent growth reduc-
tion of the shoots caused by amiben at the different nitro-

gen and pH levels.

18
I. Herbicide Absorption by
Roots

To determine if the phytotoxicity differences in
various nutrient solutions were due to nutrient effects on
herbicide entry into the root, the effects of mineral nu-
trition on herbicide absorption were investigated. By
using radioactive herbicides, the quantity of herbicide
entering a plant at nontoxic concentrations was measured.
This made possible the determination of nutrient influence
on herbicide uptake separate from the physiological effects‘
of the herbicide which could affect subsequent herbicide
absorption (Crafts, 1959). The system did not measure an
interaction between a nutrient and the herbicide on phyto-
toxicity within the plant since the treatment period was
short.

A preliminary trial indicated that a treatment
period of 4 hr to 5-day old corn, 7-day old soybeans, and
14-day old pigweed plants in nutrient solutions containing
0.5uc radioactivity per 100 m1 nutrient solution gave suf-
ficient radioactivity in the roots for accurate detection.

Roots of 'Harosoy 63' soybeans, 'WF9 X OHSlA!
single cross.corn, and redroot pigweed (Amaranthus £25327
flexus L.) were treated with 14C-labeled herbicides in
various nutrient combinations and levels. Prior to treats
ment, the plants were grown in quartz sand with complete

Hoagland's-# 1 nutrient solution. They were germinated

19

under 21/27 C night/day temperatures with 35% daytime re-
lative humidity under a 14 hr photoperiod of 2950 ft-c.

The plants were removed from the sand as carefully as pos-
sible but some root damage did occur, especially with corn.
The roots were rinsed three times in distilled water,
blotted on tissue to remove excess water, and then placed
in 70 X'21 mm shell vials containing 10 ml of the treat-
ment solution.

The treatments were 0, 10 and 50 mM NOS; 0,.1 and
5 mM PO4‘; and 0, 5 and 25 mM K+ which are 0, IX and 5X the
quantities of each nutrient recommended in Hoagland's # 1
solution, respectively. Nitrogen was supplied as-KNO3 and
Ca(NO3)2, phosphorus as Ca(H2PO4)2, and potassium as K2804.
The solutions were complete for all other elements, includ-
ing the micronutrients, so that there would be no serious
nutrient imbalances which might affect selective ion ab-
sorption (Epstein, 1961; Elzam and Epstein, 1965). Solu-
tion pH was brought to 6.0 with 0.1 N NaOH.

The radioactive carbon position and specific activ-~
ity for the herbicides were as follows: carboxy-labeled
amiben-14C, 2.19 mc/mM; uniformly ring-labeled atrazine-14C.
1.32 mc/mM; and carbonyl-labeled linuron-14C, 1.70 mc/mM.

Two herbicide concentrations were used, one which
was nontoxic and another which would cause a growth reduc-
tion of 50% to susceptible plants grown 3 weeks with the.

herbicide. Tne nontoxic concentrations were prepared with

20

the undiluted labeled materials to give .5uc-radioactivity/
100 ml nutrient solution. Thus the molar concentration is
dependent upon the specific activity of the labeled com-
pounds. The-nontoxic concentrations were 2.3 X 10"6 M
amiben, 3.8 X 10"6 M atrazine, and 2.9 X 10'6 M linuron

and the GRSO concentration was 10 X 10‘6 M for all three
herbicides. Nonlabeled technical material was added to

the labeled materials to prepare the 10 X 10"6 M solutions.

After the 4 hr treatment period, the plants were
removed from the vials, the roots rinsed 3 times in dis-
tilled water, blotted dry on tissue, cut from the plant,
and wrapped in preweighed sample wrappers which were sub-
sequently used in the Schoniger oxygen combustion tech-
nique for carbon-14 analysis. The roots were dried at 60
C for 24 hr and weighed. The entire root system from each
plant was analyzed.

To determine if any herbicide-14C molecules were
adsorbed only to the outside of the root and were not re-
moved by rinsing, the roots of several plants of each
species were immersed in a treatment solution of each
herbicide. After 5 - 10 sec the roots were removed and
washed as described above. Analysis confirmed that essen-
tially no herbicide was adsorbed to the outside of the
root that was not removed by the triple rinsing technique.

The analysis technique was basically the.Schoniger

combustion method of Wang and Willis (1965). The paper

21

containing a plant sample was placed in a nichrome wire
basket attached to a 14 cm length of nichrome wire. The
wire was inserted into a # 8 rubber stopper and the stop-
per and basket were placed in a one-liter suction flask

and a vacuum drawn. The flask was then filled with oxygen
and evacuated three times. It was then clamped off,

placed in-a Thomas-Ogg infrared combustion chamber, and
ignited. The evolved 14C02 was absorbed by 20 ml ethanol-
amine-ethanol solution, 1:2 (v/v). The trapping solution
was injected into the flask through a serum vial cap in a

4 X 80 mm glass tube in the rubber stopper.. Five milli-
liters of the solution were removed 30 min later and placed
in a scintillation counting vial with 10 m1 scintillation
solution containing 5.0 g 2,5-diphenyloxazole (PPO) and

0.3 g 2-p-phenylene-bis(5-phenyloxazole) (POPOP) in 1 liter.
toluene. The vials were placed in a Packard tri-carb
liquid scintillation spectrometer and 10 min counts taken.
Color and chemical quenching were determined using internal
toluene-14C standards and the channels ratio method (Her-
gerg, 1965). The counting efficiency was consistently be-
tween 71.1 and 72.8%.

The counts per minute were converted to disinte-
grations per minute per mg plant root tissue (dpm/mg).
Combustion efficiency was determined by spotting known
quantities of the labeled herbicides directly on sample

wrappers. The percent recovery for each herbicide was

22

consistently 92-95%. Since this is quite high, no correc-
tion was made for the missing 5-8% radioactivity. Analysis
of variance was performed on the data and planned compari-
sons made to determine the treatment effects.

Experiments were designed to study the effects of
nitrogen source and solution pH on the absorption of ami-
ben by corn and pigweed roots. Two levels of nitrate (N03)
and ammonium (NHZ), 10 and 50 mM, and a solution with no
nitrogen were mixed in all combinations with five pH
values, 4.0, 5.0, 6.0, 7.0 and 8.0. Solutions were mixed
and the pH's adjusted just prior to treatment to reduce
the possibility of-microbial effects upon the nitrogen lev-
el and pH of the solutions. The factorial design was com-
pletely randomized in two replications. The treatment
time was 4 hr and the amiben concentration was 2.3 X 10"6
M with a radioactivity of 0.5 uc/lOO ml solution. The corn
and pigweed plants were treated and the roots analyzed as
described previously. The results were analyzed and or-

thogonal comparisons were made.

II. Amiben Absorption by Corn
Coleoptiles

An experiment was initiated to determine if amiben
absorption by corn shoots was similar to root absorption
in solutions of different nitrogen sources and levels and

different pH values. In order to use intact coleoptiles,

23

a technique was developed whereby only the unbroken coleop-
tiles of corn were treated. Three corn seeds, 'WF9 X
OH51A', were placed on 2 cm of quartz sand in 6 oz styro-
foam cups. A hole was punched in the side of each cup 2
cm from the bottom so excess water could drain. The cups
were then filled with vermiculite, watered with complete
Hoagland's solution and placed in a dark controlled en-
vironment chamber for 3 days with 12 hr 27 C and 12 hr 22
C. The chamber was kept dark to simulate underground
growing conditions so that the true leaves would not pene-
trate the coleoptile. After 3 days the coleoptiles were
25-35 mm long and were suitable for treatment.

The cups were cut down the side vertically to 2 cm
from the bottom and then cut completely around at this
height. The top portion of the cup was discarded and the
vermiculite was carefully removed around the coleoptiles.
The two most uniform coleoptiles were selected for treat-
ment. A moderate quantity of "stainless putty" (Sure Seal
Products Co., Chicago 22, Ill.) was applied around the base
of each coleoptile to form a water tight seal. A 5 cm sec-
tion of plastic drinking straw was then placed over the
coleoptile and into the putty base. The treatment solution
was pipetted into the straw until the liquid was approxi-
mately 10 mm above the coleoptile tip. The treatments
were 0, 10, and 50 mM of either N03 or NH: in all combin-

ations with pH's 4.0 to 8.0 as in the previous root

24

absorption experiment. The level of the solution was
marked on the straw so that leaks could be detected. The
cups were again placed in the dark chamber at 27 C. After
90 min the straws were removed. A preliminary experiment
indicated that during longer treatment periods leaks de-
veloped around the coleoptile base. The coleOptiles were
cut at the base of the treated area. They were rinsed
three times in distilled water and blotted dry. Their
length was recorded and they were then placed in preweighed
sample wrappers. Analysis for the radioactive amiben was
performed as it was with the root tissue.

This technique provided uniform plant coleoptiles
and there were no problems treating intact coleoptiles for
relatively short periods. One disadvantage of the system
was that only a small quantity of treatment solution could
be applied. This could be a problem if absorption was
very rapid and the concentration of the external solution
changed to significantly lower levels. This was not a
problem with amiben in these experiments since the rate of

uptake was relatively slow.

RESULTS AND DISCUSSION

Concentrations of 4 and 8 ppm amiben were necessary
to obtain a GRSO value while all levels of atrazine were
well above this value (Figures I and II). Based on this
information, 4 and 8 ppm amiben and 1 and 2 ppm atrazine
were used in the following experiment.

The results were analyzed by planned comparisons so
that specific effects could be observed. The main effects
were the herbicide rates and the nutrient combinations, and
the remaining degrees of freedom for treatments are the in-
teraction effects (Tables I and II, Appendix).

For amiben, a highly significant linear relation-
ship was observed between concentration and percent reduc-
tion in dry weight of the cat shoots. Only the absence of
N in the nutrient solution caused a significantly different
response than the complete nutrient solution. With no N,
the phytotoxicity of the amiben was greatly reduced.

There was a significant interaction with the linear
effects of amiben and the NPK vs -N comparison. Comparing
the percent dry weight reductions for the NPK nutrient so-
lution at all three herbicide levels with the values for -N
shows that the reduction is much less at 4 ppm amiben than
atv8 and 16 ppm.

25

DRY WT REDUCTION, °lo

 

26

75 NPK—e
7° , 45""
65 _P_,’/’ “K
I". ” t/
60 ,7 / I”
55 - .I‘ ‘m' /
t/ , s?"
50 [I ,t’
I‘
l
‘l!5 fly, I”””’
I" I
t I
40 1’
35 . 1/
1”
30
log
4 8 l6

PPm AMIBEN

Figure I. Phytotoxicity of amiben to oats grown in sand
culture 3 weeks in complete and nutrient de—
ficient solutions

DRY WT REDUCTION, °/o

85

80

75

7O

65

60

55

50

27

 

t—————-I-————-l log

4

Figure II.

8 l6
ppm ATRAZINE

Phytotoxicity of atrazine to oats
grown in sand culture 3 weeks in
complete and nutrient deficient
solutions

28

There is a highly significant quadratic X NPK vs
-P interaction due to the reversal of the phosphorus effect
at 8 ppm of amiben. Amiben at 4 and 16 ppm was less phyto-
toxic with no P than with NPK, but at 8 ppm it was more
phytotoxic with no P. No explanation is proposed for this
interaction as it was not observed in subsequent experi-
ments.

The levels of atrazine were all too high to give a
GRSO' and yet there was a significant linear effect (Table
II, Appendix). There were highly significant differences
between the complete solution and the lack of either N or
K. The absence of P had no effect upon the toxicity to
cats.

The absence of N (Figure II) greatly reduced the
phytotoxicity of atrazine. Dry weight reductions in the
cat shoots with K absent at 4 ppm atrazine were.signifi-
cantly lower than at 8 and 16 ppm. No explanation of this
latter interaction is proposed.

Therefore, the important effect is that no N in the
nutrient solution greatly reduces amiben and atrazine
phytotoxicity to cats grown in sand culture.

A factorial experiment with three levels of N, P,

K and amiben, atrazine, and linuron was designed to deter-
mdne any interactions between the nutrients and herbicide
phytotoxicity. For all herbicides, the only meaningful in-

teractions were with N (Tables III, IV, and V, Appendix).

29

The interaction effect was the same: the phytotoxicity in-
creased as the N level increased. There were no interac-
tions with either P or K as observed in the first experi-
ment with amiben and atrazine.

As expected, increasing the amiben rate increased
the injury ratings. As the N level increased, dry weights
also increased. Even though the main effect of increasing
N on injury ratings appeared to decrease the injury, inter-
pretation of the N and amiben interaction (Figure IIIa) re-
vealed a different effect on injury ratings. The symptoms
of N deficiency in plants growing with zero N were not
distinguishable from the symptoms of amiben injury. This
accounts for an apparent injury rating of 2.0 for the zero
N and zero amiben treatment. If we assume that the plants
growing in.4 and 8 ppm amiben and zero N express the same
degree of N deficiency symptoms plus the herbicide damage,
the 0 mM N03 line can be corrected to show only the herbicide
injury and not the deficiency symptoms by subtracting 2.0
from the injury rating at all three amiben levels. This
brings the zero level N injury ratings at all three amiben
levels below the injury ratings for 5 and 10 mM NOS. There
were no observable N deficiency symptoms at either 5 or 10
mM N03 and no adjustment is required for these treatments.

That amiben was more toxic as the N level increased
can also be supported by comparing the sloPes of the three

lines in Figure IIIa. The degree of plant injury increased

mg dry wt / IO shoots

injury

30

 

  
 
  

5
T.
4 0 mM NITRA E—3_::’q
0- ..ul" 1’ at
t- :3 "¢’ "¢’1;mfl"
a! .p 1‘
1’ 4’
as...” ,6‘240 mu NITRATE
2: 1’
mama?
I ’9.
¢$’
O 4 8
ppm AMIBEN
Figure IIIa. Interactions of amiben and nitrate
on the injury of oat shoots grown in
3 weeks in sand culture (0=no injury;
lO=complete kill)
400
[ l0 ml NITRATE
300
5 NM
NITRATE 2‘
200 A
o m NITRATE -/

IOO

 

O 4 8

ppm AMIBEN

Figure IIIb. Interactions of amiben and nitrate on
the dry weight of oat shoots grown 3
weeks in sand culture

31

more rapidly (i.e. the slope of the lines is greater) for
the 5 and 10 mM N03 lines than it did for the 0 mM N03
line. As amiben was increased from 0 to 4 and 8 ppm, the
absolute value of the difference in injury ratings between
the-two amiben rates for a given N level was greater for 5
and 10 mM NOS than for no N. With no N, there was a slight.
dry weight stimulation as the amiben increased from 0 to 4
ppm. Even 8 ppm amiben did not reduce shoot growth with
zero N. However, with N present, amiben was significantly
more phytotoxic and the dry weight reduction was even
greater with 10 mM N03 than with 5 mM.

The main effects of atrazine on the injury ratings
and dry weight of the cats were the same as those for ami-
ben (Table IV, Appendix). Injury ratings were different
between all.three atrazine rates. There was a reduction
in the dry weight of oats between the 0 and 1 ppm rates
with no differences between 1 and 2 ppm. As the N level
increased, the dry weight increased at all three levels and
the injury rating increased also. This statement appears
contradictory in that both injury and dry weights in-
creased as the NO3-N level increased. I

There were highly significant differences in the
injury ratings at l and 2 ppm atrazine between the 0 mM
N03 level and the 5 and 10 mM levels (Figures IVa and IVb).

There were no significant differences between 5 and 10 mM

N03 on plant injury. The significant interaction effects

Figure IVa.

32

9 0 mM NITRATE -o","‘
[I
I
8 5 mM NITRATE w
I
7 e”
4’
’v’ No mM NITRATE
6 ,e’
a I
.5 ’
. 4°- 5 ’I
4 I
>. «I
‘5 I
I? 3
2 I

l 2
ppm ATRAZINE

Interactions of atrazine and nitrate on
the injury of oat shoots grown 3 weeks in
sand culture (0=no injury; lO=complete
kill)

33

400

  
 
 
 
 

300
ID mM NITRATE

200
5 mM NITRATE

IOO

 

mg dry wt/IO shoots

kO mM NITRATE

O l 2

 

ppm ATRAZINE

Figure IVb. Interactions of atrazine and nitrate on the
dry weight of oat shoots grown 3 weeks in
sand culture

34

on dry weight (Figure IVb) shows there was much greater
reduction in weight when N was present. The interaction
between the 5 mM and 10 mM N05 and 0 vs 1 and 2 ppm atra—
zine was also highly significant.

Two points are of particular interest. Without N,
atrazine reduced the cat growth relatively little. These
oats were obviously affected by the absence of N and this
deficiency prevented as great an expression of atrazine
phytotoxicity. The triazines inhibit the Hill reaction of
photosynthesis (Moreland, Gentner, Hilton and Hill, 1959).
When N was limiting the importance of photosynthesis was
probably reduced since the rate of vegetative growth was
less and thus the atrazine appeared less phytotoxic than
when N was abundant.

The other point is that for all three N rates, the
growth of the oats was reduced the same extent when atra-
zine was present. It seems possible that the lines for»
the 5 and 10 mM N03 rates could have been parallel (Figure
IVb) but atrazine at all three rates prevented the cats
from producing more than a given dry weight at all N levels.

The-question of how N caused greater plant injury
and also increased plant weight still remains. It is known
that N stimulates vegetative growth which is dependent upe
on a functional photosynthetic mechanism. Thus plants sup-
plied with high N levels initially grew more rapidly and

increased in weight over those plants at the zero N level.

35

These same plants also became dependent upon assimilated
materials sooner than the others; and when atrazine was
present, these plants were not able to supply the products
normally available from photosynthesis. Thus the symptoms
of atrazine phytotoxicity appeared sooner in the life cycle
of plants supplied with N than in those without it. The
injury ratings therefore increased as the N rate increased
since the higher N levels caused the plants to become de-
pendent upon photosynthesis earlier.

The response of cats to linuron under different N
levels as determined by injury ratings and dry weights was
identical to that of atrazine. The main effects of linuron
and N show injury increased significantly for all three
linuron and N rates. Linuron greatly reduced the dry
weight of oat shoots, but there was no difference in the
reduction between the 1 and 2 ppm rates. The presence of
N significantly increased the dry weight above 0 mM N03,
but there was no difference in weight between 5 and 10 mM
N03.

As with atrazine and amiben, only the N and linuron
interactions were significant. Figure Va shows that
linuron was significantly more phytotoxic with than with-
out N and that there was also more injury at 10 mM NOS than
at 5 mM. The dry weight reductions (Figure Vb) increased
as the N levels increased and they were reduced to the

same value by both 1 and 2 ppm linuron.

36

s
.a
7 I0 mM NITRATE jv"
.4’ 4’
"“¢"’ 1’
6 l’ I’
l’ v’
t I
2 5 I ,4-5 mM. NITRATE
': I ,e
O

 

O I .2
ppm LINURON

Figure Va. Interactions of linuron and nitrate on the
injury of oat shoots grown 3 weeks in sand
culture (0=no injury; lO=complete kill)

37

320

   
  

G-IO mM NITRATE

240

5 mM NITRATE
l60

  

NITRATE -9

00
C)

mg dry wt/IO shoots

 

O I 2
ppm LINURON

Figure Vb. Interactions of linuron and nitrate on the
dry weight of oat shoots grown 3 weeks in
sand culture

38

There were no interactions between the three N and the l
and 2 ppm linuron levels.

The fact that the linuron interactions with N are
identical to those of atrazine is not surprising since
linuron too is an inhibitor of the Hill reaction (Cooke,
1956). Therefore the explanation of why both the injury
rating and dry weights of oats increased as the N level
increased is the same as the previous discussion for
atrazine.

No P or K interactions on phytotoxicity were
found. It was not possible to isolate the mechanism of
the N interaction in bioassay studies of this type. Either
the increased susceptibility to herbicides was due to an
interaction of the herbicide and N within the plant or the.
N level of the solution influenced the amount of herbicide
entering a plant. The herbicide absorption experiments
were designed to determine nutrient status effects on herb-
icide entry into plants. _

The experiments which measured herbicide absorption
by roots showed that amiben uptake (Table l) in both corn
and pigweed decreased significantly with_the addition of
N05. There were no significant differences between the 10
and 50 mM N03 rates..

The addition of NOS had no effect on atrazine up-

take (Table 2) by corn or pigweed. There was a significant

39

 

Hm I am no

(msm.z,s0fixm>b

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

one. ,oao. «as _He~ 5mm. mom
mm mm em emu hem Hem «em «mm mom own
mm em mm «mm m3 o3 emu! Sm mom «2. mm
mm mm mm amt. ,aom men men . mam «on as m
mm as mm «mm was was ANN mma mom o
Edamnmuom
no , as me mos new mom ~m~ vmm mm~ m>m
me so cm was «am one .smm mam mom as m
mm mm mm mam omm con .mmm ham cam .2s a
me so mm was won pom «mm mmm «mm o
modemwonm
no on no mmo some mmo .tem mom mam mph
om am mo met «No new mmm can mmm as on
mm mm mm mom mam one omm so” emm as as
me on on «on new ems com mmm com o
mumuuaz
m>m on m.~ m>m ca m.~ m>m on m.~ z ouoa x
cocoo conwfid
coosmflm masonmom cuou
#3 who .uoou mE\Emc .coflumHOmnm cognac
cowuoHOm

unmanned on» Ca mHo>oH Edammmuom can .msuonmmonm .cowonuflc an coocmoaw

use on as w cw muoou cowthmmswcmi.mcmomhom .cuoo an cOwumHomQMIU¢H|cmnw£¢

.MH.OHQMB

 

40

.mao>wuoommmu .mao>oa.wa can m may no unmowmwcmwmas .«

 

 

 

 

 

 

 

 

m2 .m2 m2 .essmmmuom ze mm m> m x mm m> a:
m2 m2 m2 Esammcuom SE mm can m m> o x mm n> Hm
m2 m2 m2 cumsmmonm 28 m m>-a x mm,m>,am
mz mz mz ensconced cs m can H m> o x mm m> am
m2 mz « mummy“: 2E om m> oa x mm m> Hm
mz t mz humans: as om can on m> o x mm m> Hm
measuocuoucw x.m.z x cona8¢
m2 m2 m2 Edwmmcuom 28 mm m> m
m2 m2 m2 Esfimmmuom 25 mm can m m> o
«t « mz oumnmmonm 25 m m> a
mz «« mz oumcmmocm 2E m can a m> o
m2 m2 m2 oumnuac SE om m> oa
ts m2 «r OHMHHAG SE om 6G6 0H m> o
.muoommo came Msm.z
mz .. mz assess last 2 ones x OH m> Name 2 once x m.~
uoommo ouch cooflE«
mmo3mam memonwmm cfimm
moccOAHAQmam consummEoo
mcoflusHom

ucoflnunc CH muoou newsman can mcmonmom .cuoo an coaumuomom U alcooflfim co
mcofluomuoucw names can muoommo ucoflnuo: can assess mo mGOmfium Eoo woodman .oH manna

 

 

 

 

 

 

 

 

 

 

 

41

 

 

 

 

 

 

 

 

 

 

eae How . awe . ewe oee mme s.m.z Ham m>m
«me eom owe ewe _ eke .oee w.. . use
eme can pee eke mme mme ‘ emu mom mom zssmms
eke nee ape eme ewe «om men oem «mm as m
mom mew mwe ewe awe ewe mmm mmm emm o
Edemmmuom
new ‘ one cow ewe eke mom mme mmm mmm m>m
ewe mme "he ewe eme mom. can see mmm 2s m
Nee mme one eme ewe mom mmm mmm oem as e
mew mam eme ome ewe com mmm ee~ emu o
= homeomoem
use eee owe . owe mme mom Nee eem mmm‘ m>m
ome pom nae mme eme mom wee . mmm eem .zs om
mme eme «we eae use «on mew eem men :5 as
we owe mom nee «me eme emw mmm ham o
_oumnuez
_m>m oe m.m m>m oe m.m m>m oe mxm. 2 once x
GOCOU GGflNMHU¢
cmozuem mammnwom CHOU

 

 

 

 

 

93 who .uoou mE\Emc .coHumHOmnm ocwnmuue

 

 

 

.cowu5H0m
ucmeuvsc on» as mao>oa Edemmmuom can .mcuoammonmr.comonpec an coocosamce
mm as e ca muOOH coosbflm cum .mcmmnhom .cnbo hn.noevmhpmnm OeanmbHNMHum .mm wanna,

42

.>+m>wuoommou .mao>oa we can m oz» no unmoemesmHMts.e

bl D 7’

 

 

 

 

m2 mz « Edemmcuom SE mm u> m x mm m> Hm
m2 m2 m2 scammmuom 25 mm can m m> o x mm m> Hm
m2 m2 m2 mumaomoao as m m> e a ma m> ea
«« m2 m2 mumammoam as m can e m> o x «a m> ea
m2 m2 m2 mousse: as om m> oe x ma.m> ea
m2 m2 m2 mumuuec as om can oe m> o x «a m> ea
msoeuomuouce &.m.z x ocfiumuum
m2 m2 m2 soemmmuom SE mm m> m
mz mz mz ssemmmuom as mm one m m> 0
m2 mz mz oumnmmonm SE m m> H
4 m2 m2 mueaamoaa as m one e m> o
m2 m2 m2 avenues :8 om m> oe
mz e mz oneness as om one oe m> o
muoommo cede x.m.z
mz «e mz mceumuum away once x as m> neat a muse x e.m
uoommo mums onenmnud
cmm3mHmI msmonmo choc.

 

oosmoemes em

 

coweucmEoo

 

mGOeuoHom ucoenuss

ca muoou coo3mem use smmnMOm .cnoo an GOeumHOmnm UeHImsenmuum so msoeu
nonsense news» can muoommo acmenuss can oceucuum mo mnemenomsoo cossmam ..n~ manna

43

decrease in atrazine uptake by soybeans caused by 3.8 X
10'6 M atrazine when compared to the 10 X 10"6 M rate.

Nitrogen had no effect on linuron absorption (Table
3) by soybeans and pigweed. With corn there was a significant
decrease in uptake between the 10 mM and 50 mM NO} levels.
for both herbicide rates. Higher N may have stimulated
the overall physiological processes of the plant, but
whether the plants responded to this during a 4 hr treat-
ment is doubtful. The expected effect would be an increase
in ion absorption and not a decrease. The results could
be explained by competition for uptake sites. As the N03
level increased from 10 to 50 mM, the absorption of linuron
decreased because fewer carrier sites were available. This
observation is also in agreement with Stein's (1967) state-
ment that the flow of one substrate can stimulate the flow
of another in the opposite direction.

Phosphorus had no effect on amiben absorption
(Table l) by corn, but its presence decreased amiben uptake
significantly in soybeans. Comparing zero PO4- to 1 and 5
mM POZ- for pigweed, there were no significant differences.
However, 1 mM Poi- significantly decreased amiben uptake
when compared to the uptake at 5 mM. The same trend was
present in soybeans.

Atrazine uptake (Table 2) by corn and soybeans was

unaffected by P, but the presence of P decreased atrazine

uptake by pigweed. There was a significant interaction

44

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

wwm ewe swm . wwe. eww wwe mew mew eww. s.w.z now w>m
wwm eem ,wwm wwe eww eww www‘ www eww, .msm
new wmw ewe eww wee www l www www eww as mm
wem wwm mwm we» www was www www www as m.
wee wee ewe wme . sww mew www www mew w
. ademmcuom.
wem wwe ,ewm www www . new www eww wmw w>w.
ewe wwe awe wmw who www wew www www as m
wwe , wwm ewe ems mew www www wew www as e
New New .ehe eea new wwe www www www w
manganese
wwm ewm wwe ewe eww News www eww .ehw ‘ w>m
wwe wwm ewm ewe eww wwe eew ewew eew as wm
www www wwm ewe www www www www wwe as we
wwe ewe wwe ewe www wew www www www w
mumuuez
m>w we w.w, m>m we w.w w>m , we w.w a wuwe a
. socoo sounded
comsmem . msconmom . suoo.
D3 mac .uoou ms\smc .c0eumnomnm counseq

 

 

 

 

soHuoeom
usoeuuac on» as meo>ma Edemmmuom can .msnonmmonm..comouuec an cmoswusce
on us e as muoou coo3mem can .msmmn>0m xenon MD cowpthmDN,UeHIGOHbfifln .Mm mmflmfi

45

.>Ho>euommmou .neo>oe we use m on» us ucmoemesmemas.s

 

wz wz wz ssewwwuoa as we w» w a Ma w> ea
.m2 m2 m2 soemmmuom 2E mm was m m> o x m m> a:
ma «s wz muwaamoaa as.m w> e a ma m> “a
«« mz wz oumaomoao as m can e w» w a a w> a
m2 m2 m2 obtuse: as wm m> we a «a w> ea
mz mz mz . avenue: 28 on can oe m> o x mm m> em

 

mcoHuomuouce M.m.z.x counsee

 

 

 

 

wz « wz ssewmmuom as mw.w> m

m2 m2 m2 ssemwmuoa as mm one m w> w

mz «a m2 oumnmmonm 28 m m> H

wz mz wz mumsawoaa as m was e w> w

m2 m2 a ousuues SE om m> oe

m2 m2 mz oumuuec as om can oe m> o
muoommo secs M.m.z

mz we mz soussee Away a wuwe x we m> neav a wuwe x w.~
.uoommo mums conscee

moosmem osmonhom snow
oocmowmecmem soweummsou

 

.msoepseom
ucoeuusc Ge mnoou coo3mwm csm scon>0m .suoo an c0eumH0mnm 0e Iconocee so
mcoeuomuouse semen can muoouwm ucoenuos can counsee mo msomeummsoo nonspem .om sense

46

with pigweed between the two atrazine concentrations and
the 0 vs the l and 5 mM P02" levels.

Linuron uptake (Table 3) by corn was unaffected by
P treatment. For the soybeans there was a highly signifi-
cant interaction between the linuron concentration and the
1 and 5 mM PO4- levels. With 2.9 X 10'6 M linuron, the 5
mM POE- rate reduced the uptake of linuron as compared to
the 1 mM PO4- treatment. With 10 x 10'6 M linuron in the
solution, uptake was unaffected as the P level changed.
This was opposite the response of the amiben and P level
interaction. Thus the herbicide uptake responses to P
seemed to vary with species, herbicide, and herbicide and
P concentration. This was further illustrated in the case
of linuron uptake by pigweed. There was a reversal in the
P effect between the two linuron levels. At the zero P02-

rate and 2.9 X 10-6 M linuron, absorption of linuron was
3-

increased by'l and 5 mM PO4 . Although, the uptake of
linuron at the zero P02- level in 10 X 10'6 M linuron was

greatly reduced when compared to the l and 5 mM P03- rates.
The nature of the P effects on herbicide absorption is by
no means clear.

Changes in the K concentration of the nutrient so-
lution had no significant effects on amiben absorption at
either level of amiben in any species (Table 1). There

were no significant main effects of K on atrazine or

linuron absorption by soybeans, corn or pigweed.

47

A consistent effect.observed was the decreased
amiben absorption in the presence of N by the susceptible
species, corn and pigweed. It seemed important to study
this further and to determine the influence of solution pH
and the source of nitrogen on amiben uptake.

The experiment to determine the effects of N level
and source showed highly significant interactions between
the rates and sources of N and the nutrient solution pH
for amiben-14C uptake by corn roots (Figure VI). The
orthogonal comparisons revealed highly significant differ-
ences between the nitrate and ammonium forms of N and these
interacted with the highly significant linear pH effects
(Table VI, Appendix). More amiben was taken up by corn
with ammonium sulfate as the source of N than with potassi-
um.and calcium nitrate. No such interactions were noted
in the case of amiben uptake by pigweed due perhaps to much
more plant to plant variation in uptake.

The effect is due to the differences in the source
of N since sulfate, potassium and calcium were present in
both the nitrate and ammonium solutions. This effect was
opposite to the one reported by McReynolds and Tweedy
(1969) in which approximately twice as much simazine-14C
was translocated to the shoots of plants, grown in NO3-N
than in NH4-N. Their plants were grown 4 days in solutions
of simazine and therefore the differences probably reflect

secondary effects and not differences in absorption alone.

“In I ma root,dry wt

dpm/mg root, dry it

Figure VI.

 

(a)

(b)

48

CORN
_ NO NITROGEN
---| IOII‘IM NITRATE
‘ .49 50ml! NITRATE
‘ "V-DOII'IHAMMONIW
\

sow'rIou pH

Interaction of source and rate of nitrogen

with solution pH on amiben- C uptake in 4
hr from nutrient solutions by corn roots.
The main effect of pH on amiben-14C ab-
sorption in 4 hr by corn and pigweed roots
from a nutrient solution

49

Since they used a different herbicide, no direct compari-
sons of results are justified. However, both amiben and
simazine absorption and/or translocation seem to be af-
fected by the source of N in the culture solution.

The interactions between N source and pH could be
a reflection of the buffering capacity of the different
solutions. If the NH4-N source were a better buffer than
the NO3—N source, the high uptake at pH 4.0 for 10 and 50
mM NH: could be because the pH remained low. Perhaps in
the 10 and 50 mM NOS solutions the pH increased during the
4 hr period and the decreased uptake was a secondary_ef-
fect. Determination of the buffering capacity of all so-
lutions showed this did not occur (Table VII, Appendix).
Each solution contained phosphate and was somewhat buffer-
ed. For a given pH the buffering capacities of the N solu-
tions were relatively constant. Differential changes in
solution pH then did not affect the results.

The linear effect of pH on amiben absorption was
highly significant for both corn and pigweed (Figure VIb).
These effects were determined by the orthogonal polynomial
method where n=5 (Anderson and Houseman, 1942). Pigweed
uptake of amiben was more affected by the solution pH than
was corn uptake.

The amiben absorption response to pH changes could.
be due to any of three mechanisms. The first is simply

competitive uptake between amiben ions and the hydroxyl

50

ions as proposed by Rains, 33 31. (1964). However this
hypothesis has some practical limitations. It would seem
quite unlikely that two molecules of such unequal size (MW
amiben ion = 206, MW hydroxyl ion = 17) are taken up via
the same pathway as competition is normally observed be-
tween similar sized molecules.

The form of the amiben molecule is important in
determining its availability for absorption. Amiben can
be expected to behave as an amino acid in solution since
it has a carboxyl and amino moiety on the benzene ring.
The degree of dissociation and charge on the molecule will
change as pH changes. Since the pKl of amiben is 2.18,
the pKz is 11.65, and the isoelectric point is 6.80 (Figure
I, Appendix), the form of the ion changes from more posi-
tively charged ions at pH 4 to near neutrality at pH 7, to
a greater number-of negatively charged ions at pH 8. Ami-
ben may be taken up as a positively charged ion and the
linear decrease in absorption between pH 4 and 8 corres-
ponds to the linear change in the titration curve for ami-
ben in this pH range.

The increases in solution pH may have injured the
plant roots. However, injury would be more likely to occur
at the very low (pH 4) or high (pH 8) pH values relative
to the normal soil solution pH of 5-7 for the maximum
growth of most plants. Since the treatment time was only

4 hr, plant injury was not visible, yet the carrier system

51

for amiben could have been injured by the increasing
hydroxyl ion concentration.

As the solution pH increased from 5 to 7, amiben
absorption decreased 29.5 and 73.2% for corn and pigweed
respectively. These pH values are found in the field and
if the same effect on amiben absorption occurs there, it
may explain a lack of good weed control at pH 7 or the
presence of crop injury at pH 5.

A NO3-N source reduced amiben uptake by corn roots
while an NH4-N source increased it. Perhaps the uptake of
nitrate reduced amiben absorption according to the scheme
of Stein.mentioned earlier, i.e. an increase in the uptake
of one substrate decreased the uptake of another.. Nitrate
uptake might increase while reducing amiben absorption.

No explanation of the NH: effect is prOposed.

Coleoptile absorption of amiben was measured in two
ways, dpm/mm and dpm/mg coleoptile. Expressing the data
as dpm/mg accounted for more variation than expressing it
as dpm/mm. The surface area of the coleoptile is evident-
ly more important in determining herbicide absorption than
is the length. Coleoptile length and surface area are
correlated, but the weight (which is a function of both
length and diameter) provides a better estimate of surface
area and therefore explains more of the treatment variation.

Amiben-14C uptake by corn coleoptiles is both

strikingly similar to and different than root absorption.

52

The effect of pH on amiben absorption by corn coleoptiles

is very similar to the effect on root uptake. As pH in-
creases, amiben uptake decreases and the analysis of var-
iance shows that the linear effect of pH was highly signi-
ficant while none of the higher order polynomials were sig-
nificant. Increasing the pH from 5.0 to 7.0 decreased

corn coleoptile absorption of amiben 30.5%. This is near-
ly identical to the 29.5% reduction in corn root absorption
caused by the same pH change. This suggests that the same
mechanism is operative in both root and shoot amiben uptake.

Nitrogen source and rate have no effect on amiben
absorption by the coleOptile (Table 4). Since roots are
the principal if not exclusive site of nutrient uptake from
the-soil, the lack of a nutrient effect on shoot uptake of
a herbicide is logical.

It is important to compare the quantity of herbi-
cide absorbed by the corn root system to that of the cole-
optile. Expressing the overall means for the root and
shoot uptake on an equal time basis showed the shoots and
roots absorb 23.3 and 103.1 dpm/mg per hour respectively.
Some caution must be used in this comparison as 5-day old
plants were used in the root trials while 3-day old plants
were used in the shoot absorption trials. The fact that
the roots took up 443% more amiben than the shoots
might be a reflection of the younger age and size of the

coleoptiles. However, the coleoptiles were nearly as large

53

Table 4. Amiben-14C absorption by corn coleoptiles in 90
min as influenced by solution pH and nitrogen
source and level

 

pH of dpm/mg coleoptile, Nitrogen dpm/mg coleoptile,
solution dry wt solution dry wt

4.0 51.8 control 35.2

5.0 37.0 10mM NOS 34.1

6.0 34.1 50mM N03 34.4

7.0 25.7 lOmM NH: 35.7

8.0 25.8 50mM NH: 34.9

 

 

 

as they would become in field conditions and they had prob-
ably reached the stage of maximum herbicide absorption.
“Even though corn coleoptiles appear to absorb much
less amiben than the roots, the degree of phytotoxicity
can not be determined from these experiments. The concen-
tration of amiben absorbed by the coleoptiles may cause
great.phytotoxic effects. Stoller and Wax (1968) report
relatively little upward translocation of amiben in morning

glory (Ipomoea hederacea L.), velvet leaf (Abutilon theo-

 

phrasti Medic.), white beans, barley (Hordeum vulgare L.),
carrots, tomatoes, and sugar beets (2333 vulgaris L.).
Translocation differences did not explain the selectivity
of amiben. Since little amiben is translocated, its mode
of action may occur in the roots. Then phytotoxicity would

not depend on translocation to the shoot and this might

54

explain why Knake (1968) found shoot uptake of amiben by
giant foxtail less phytotoxic than root uptake. Variation
in uptake from species to species and chemical to chemical
make specific statements concerning shoot uptake at this
point impossible, although shoot uptake is an important.
process in the expression of phytotoxicity for many chem-
icals in several species (Knake, 1967, 1968; Appleby and
Furtick, 1965; and Appleby et_gl.l965).

Amiben phytotoxicity was studied in a bioassay ex-
periment with two sources of nitrogen, N03 and NH1, since
the first two bioassays used only N03. Phytotoxicity in-
creased when NHZ was the N source (Table 5). With 8 ppm
amiben the injury ratings and percent shoot reductions of
oats were significantly increased by 10 and 50 mM NHT. In
this experiment N-serve was added to the NOS solutions to
prevent bacterial conversion of N03 to NHZ. The rate of
.1 ml N-serve/mM N03 per liter solution was itself phyto-
toxic to the oats. At 50 mM NO}, the oats were completely
killed by N-serve and the effect of amiben at various so-
lution pH's with NO} could not be determined.

It was shown that amiben phytotoxicity increased
with both N03 and NH: while amiben absorption varied with
these same treatments. Therefore, the increased phytotox-
icity observed in the bioassay experiments was not caused

by increased amiben absorption in N03 solutions.

55

 

 

 

 

 

 

 

 

 

 

 

 

Table 5. Effect of pH and ammonium level on the phytotoxic-
ity of 8 ppm amiben to oats grown in sand culture
“r 4' . . T
N level Solution pH % shoot reduction Injury rating
0 4.0 63.1 4.5
0 5.0 63.0 3.5
0 6.0 53.0 4.0
0 7.0 47.1 4.5
0 8.0 53.1 3.5
avg 55.9 4.0
10 mM NH4+ 4.0 74.2 7.0
10 mM NH4* 7.0 70.1 6.0
10 mM NH4+ 8.0 66.5 4.0
avg 69.8 6.0
so mM Net 4.0 68.9 8.5
so mM NH4+ 5.0 70.1 8.5
50 mM NH'+ 6.0 77.8 8.0
avg 74.4 8.3
10 = no injury, 10 = complete kill.

 

 

SIGNIFICANCE

P “I ED COMPARISON % Shoot Reduction Injury RatIng

 

Ammonium effects

 

 

 

o N vs 10 and so mM NH4+ ** **
10 vs 50 mM NH4+ NS **
pgieffects

pH linear NS *
pH quadratic NS NS
pH cubic NS NS
pH quardic NS NS
Ammonium and pH interactions2

10 vs 50 mM NHfiTX pH linear NS **

 

2Only significant interactions are given.

*,**Significant at the 5 and 1% levels respectively.

SUMMARY AND CONCLUS IONS

Bioassay experiments with oats grown 3 weeks in
sand culture were performed to determine herbicide and
nutrient interactions with herbicide toxicity. They
showed that the toxicity of amiben, atrazine, and linuron
increased as the N03 level of the nutrient solution in-
creased. Phosphorus and potassium did not interact with
herbicide toxicity. Amiben toxicity was increased by both
N03 and NH: sources of N. Thus the application of higher
rates of fertilizer should have no negative effects on_
herbicide effectiveness and with higher N levels the tox-
icity may even increase.

To determine if the increased toxicity was due to
greater herbicide uptake, root absorption experiments in-
vestigated possible interactions on the uptake of 14-C-,
herbicides with nutrients. There were few significant in-
teractions between atrazine or linuron absorption and the
nutrient level. An important response was that NOE‘de-
creased amiben absorption by corn and pigweed roots.

This indicates that amiben's increased toxicity
at higher N03 rates in the bioassay experiments was not

due to increased amiben uptake. Since the nitrogen

56

57

level did not increase.atrazine or linuron uptake, their
greater toxicity with increased N rate also was not at the
site of uptake.

The effects of different N sources and nutrient
solution pH's on amiben uptake by corn and pigweed roots
were inVestigated. An NH: nitrogen source compared to a NO}
source increased amiben uptake in corn but not in pigweed.
Amiben absorption decreased linearly between pH 4.0 and
8.0. There were highly significant interactions between.

N source and solution pH such that the differences in ami-
ben uptake between NOB-N and NH4-N were greater at low pH
values.

These effects might have practical aspects as
nitrogen fertilization of soybeans becomes more.common.

If soybeans and weed species in the field respond to the

pH influence on amiben uptake like corn grown in nutrient
culture, the form of N fertilizer added when amiben is ap-
plied could greatly influence both weed control and crop
injury. When ammonium sulfate is the N carrier, the danger
of soybean injury might increase; whereas, with potassium
nitrate as the source of N, injury would be less likely al-
though weed control might be less than ideal. Therefore,
in addition to the many factors one must already consider
in applying herbicides, the form of nitrogen fertilizer

applied may also be important.

58

The effects of N source and solution pH on amiben-
14C absorption by intact corn coleoptiles was studied
since shoot uptake of soil applied herbicides is important.
A technique was developed to treat only intact corn coleop-
tiles.

There was a linear decrease of amiben absorption
as pH values increased from 4.0 to 8.0. Between these
values amiben changes from a positively charged ion to a
negatively charged ion which suggests that amiben is ab-
sorbed as a positively charged ion. The absorption mech-
anisms of coleoptiles and roots may be the same since their

response to pH change is identical.

Corn roots absorbed 443% more amiben than the
coleoptiles on a mg basis, which suggests that the root

may be the main site of amiben entry in corn.

LITERATURE CITED

10.

11.

LITERATURE CITED

Adams, R. 8., Jr. 1964. (Fertilizer placement cri-
tical where herbicide residues are present. Minn.
Farm and Home Sci. 22: 13-14.

. 1965. Phosphorus fertilization and the
phytotoxicity of simazine.- Weeds: 113-116.

 

Anderson, R. L. and E. E. Houseman. 1942. Tables of
orthogonal polynomial values extended to N-104.
Iowa State Res. Bull. 297: 595-672.

Appleby, A. P. and W. R. Furtick. 1965. A technique
for controlled exposure of emerging grass seed-
lings to soil-active herbicides. Weeds 13: 172-
173.

, and S. C. Fang. 1965. Soil
placement studies with EPTC and other carbamate
herbicides on Avena sativa. Weed Res. 5: 115- 122.

 

 

Bingham, S. W. and R. P. Upchurch. 1959. Some in-
teractions between nutrient level (N,P,K,Ca) and
diuron in the growth of cotton and Italian rye-
grass. Weeds 7: 167-177.

Broyer, T. C. 1956. Current views on solute move-
ment into plant roots. Proc. Amer. Soc..Hort. Sci.
67: 570-586.

Cooke, A. R. 1956. A possible mechanism of action
of the urea type.herbicides. Weeds 4: 397-398.

. 1957. Influence of 2, 4-D on the uptake
of minerals from the soil. Weeds 5: 25- 28.

Corbin, F. T. and R. P. Upchurch. 1967. Influence
of.pH on detoxification of herbicides in the soil.
Weeds 15: 370-377.

Crafts, A. S. 1939. The relation of nutrient to

toxicity of arsenic, borax and chlorate in soils.
J. Agr. Res. 58: 637-671.

59

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

60

. 1959. Further studies on comparative
mobility of labeled herbicides. Plant Physiol.
34: 613-620.

 

. 1964. Herbicide behavior in the plant,
p. 75-I10. In L. J. Audus (ed.) The physiology
and biochemistry of herbicides.. Academic Press,-
New York.

Dhillon, P. S., W. R. Byrnes and C. Merritt. 1967.
Simazine and phosphorus interactions in red pine
seedlings. Weeds 15: 339-343.

Donaldson, T. W. 1967. Absorption of herbicides
2,4-D and monuron by barley roots. Diss. Abstr.
28: 137l-B.

Elzam, O. E. and E. Epstein. 1965. Absorption of
chloride by barley roots: kinetics and selec-
tivity. Plant Physiol. 40: 620-624.

Epstein, E. 1961. The essential role of calcium in
selective cation transport by plant cells. Plant
Physiol. 36: 437-444.

Fang, S. C. and J. S. Butts. 1954. Studies in plant
metabolism.e IV. Comparative effects of 2,4-D and
other plant growth regulators on phosphorus metab-
olism in bean plants. Plant Physiol. 29: 365-368.-

Fried, M. and J. C. Noggle. 1958. Multiple site up-
take of individual cations by roots as affected by
hydrogen ion. Plant Physiol. 33: 139-144.

, and R. E. Shapiro. 1961. Soil-plant re-
lationships in ion uptake. Annu. Rev. Plant
Physiol. 12: 91-112.

 

Herberg, R. J. 1965. Channels ratio method of quench
correction in liquid scintillation counting.
Packard Tech. Bull. 15. 8p.

Hogge, E. J. 1968. The effect of linuron on 32P and
50a uptake in tomato and parsnip. Weed Sci. 16:
185- 187.

Jennings, O. H. 1963. The absorption of solutes by
plant cells. Iowa State Univ. Press, Ames. 204 p.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

61

Knake, E. L., A. P. Appleby and W. R. Furtick. 1967.
Soil incorporation and site of uptake of preemer-
gence herbicides. Weeds 15: 228-232.

, and L. M. Wax. 1968. The importance of
the shoot of giant foxtail for uptake of preemer-
gence herbicides. Weed Sci. 16: 393-395.

 

Loustalot, A. J., M P. Morris, J. Garcia and C. Pagan.
1953. 2,4-D effects on phosphorus metabolism.
SCie 118: 627-6280

McReynolds, W. D. Jr., and J. A. Tweedy. 1969. Ef-
fect of nitrogen form on the uptake and herbicidal
activity of simazine in corn, rye and soybeans.
Abstr. Weed Sci. Soc. Amer. 1969 Meeting. No. 213.

Moreland, D. E., W. A. Gentner, J. L. Hilton and K.
L. Hill. 1959. Studies on the mechanism of herbi-
cidal action‘of 2-chloro-4,6-bis(ethylamino)-s-
triazine. Plant Physiol. 34: 432-435.

Nash, R. G. 1968. Plant uptake of 14C-diuron in
modified soil. Agron. J. 60: 177-179.

Nashed, R. B. and R. O. Ilnicki. 1968. The effect
of linuron on ion uptake in corn, soybeans, and
crabgrass. Weed Sci. 16: 188-192.

Oliver, L. R. and R. E. Frans. 1968. Inhibition of
cotton and soybean roots from incorporated tri-
fluralin and persistence in soil. Weed Sci. 16:
199-2030

Pardee, A. B. 1968. Membrane transport proteins.
Sci. 162: 632-637.

Rains, D. W., W. E. Schmid and E. Epstein. 1964.
Absorption of cations by roots. Effects of hydro-
gen ions and essential role of calcium. Plant
Physiol. 39: 274-278.

Rebstock, T. L., C. L. Hamner and H. M. Sell. 1954.
The influence of 2,4-D on the phosphorus metabolism
of cranberry bean plants. (Phaseolus vulgaris).
Plant Physiol. 29: 490-491.

Ries, S. K., R. P. Larsen and A. L. Kenworthy. 1963.
The apparent influence of simazine on nitrogen
nutrition of peach and apple trees. Weeds 11:
270-273.

36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

46.

47.

62

, and A. Gast. 1965. The effects of sima-
Zine on nitrogenous components of corn. Weeds 13:,
272-273.

 

Rumberg, C. B., R. E. Engel and W. F. Meggitt. 1960.
Effect of phosphorus concentration on the absorp-
tion of arsenate by cats from nutrient solutions.
Agron. J. 52: 452-453.

Sabbe, W. E. 1967. Effect of trifluralin on uptake
of fertilizer phosphorus. Ark. Farm Res. 16: 4.

Stein, W. D. 1967. The movement of molecules across
cell membranes. Academic Press, New York. 369 p.

Stoller, E. W. and L. M. Wax. 1968. Amiben metabol-
ism and selectivity. Weed Sci. 16: 283-288.

Sutcliffe, J. F. 1962. Mineral salts absorption in
plants. Pergamon Press, New York. 44 p.

Upchurch, R. P., G. R. Ledbetter and F. L. Selman.
1963.. The interaction of phosphorus with the
phytotoxicity of soil applied herbicides. Weeds
11: 36-41.

, F. L. Selman, D. D. Mason and E. J.
Kamprath. 1966. The correlation-of.herbicidal
activity with soil and climate factors. Weeds 14:
42-49 0

Vega, M. P. 1964. The influence of phosphate on the
phytotoxicity of 3-amino-l,2,4-triazole. Diss.
Abstr. 25: 82.

Wang, C. H. and D. L. Willis. 1965. Radiotracer
methodology in biological science. Prentice-Hall,
Inc., N. J. 363 p.

Weber, J. B., P. W. Perry and K. Ibaraki. 1968.
Effect of pH on the phytotoxicity of prometryne
applied to synthetic soil media. Weed Sci. 16:
134-136.

Wort, D. J. 1962. The-application of sublethal con-
centrations of 2,4-D in combination with mineral
nutrients. World Rev. of Pest Control 1: 6-19.

APPENDIX

63

 

 

 

 

 

 

 

 

 

 

Table I. Phytotoxicity of three levels of amiben to cats
grown in a sand culture with various nutrient
solutions

Percent reduction in shoot d wt
Nutrient Amiben concnlyppmfi
Solution 4 8 16 avg
NPKl 53 59 75 62
-N2 29 so 64 47
-p2 41 66 69 59
-K2 57 55 74 62
F avg f 45 58 70 58
1Full strength Hoagland's # 1 nutrient solution.
2Full strength Hoagland's for all other essential
elements.
COMPARISON SUM of SQUARES

 

Amiben effects

Amiben, linear
Amiben, quadradic

 

 

Nutrient effects3
NPK vs -N
NPK vs -P
NPK vs -K

Amiben X nutrient interactions
Linear X NPK vs -N
Linear X NPK vs -P
Linear X NPK vs -K
Quadradic X NPK vs -N
Quadradic X NPK vs -P
Quadradic X NPK vs -K

 

3909**
2

956**
53

120*
24
22

61
254**
28

 

*,**Significant at the 5 and 1% levels respectively;

3Nonorthogonal comparisons.

64

Table II. Phytotoxicity of three levels of atrazine to
oats grown in a sand culture with various
nutrient solutions

 

 

 

 

Nutrient Percent reduction in shoot dry wt
Solution Amiben concn,¥ppm ;
4 8 ‘16 avg
'prl 84 84 83 ' 84
-N2 60 64 63 * 62
-p: 81 81 83 82

 

 

 

 

 

1

Full strength Hoagland's # l nutrient solution.

2Full strength Hoagland's for all other essential
elements.
COMPARISON SUM of SQUARES

 

Atrazine effects

 

 

Atrazine, linear 99*

Atrazine, quadradic l3
Nutrient effects3

NPK vs -N 2056**

NPK vs -P 21

NPK vs -K 308**

Atrazine X nutrient interactions

 

Linear X NPK vs -N 16
Linear X NPK vs -P 10
Linear X NPK vs -K 156*
Quadradic X NPK vs —N 0
Quadradic X NPK vs -P 2
Quadradic X NPK vs -K 4

 

*,**Significant at the 5 and 1% levels respectively;

3Nonorthogonal comparisons.

65

Table III. Amiben phytotoxicity to oats grown three weeks
in sand culture at three levels of nitrate as
measured by oat shoot injury ratings and dry

 

 

 

weights
Injury rating1 Dry wt, mg/10 shoot ’
mM Nitrate Amiben, ppm I Amiben, ppm
0 4 8 avg } 0 4 8 avg
o 2.0 3.6 4.5 3.4 i 165 192 165 174
s 0.1 2.9 4.3 2.4 I 292 209 177 226
I
10 0.5 2.6 3.8 2.3 I 363 228 192 261

 

 

 

 

avg 0.9 3.0 4.2 2.7

273 210 178 220

 

 

Significance

Planned Comparisons _
Injury Dry wt

1

 

Amiben effects

0 vs 4 and 8 ppm amiben ; ** **
4 vs 8 ppm amiben ; ** **

Nitrogen effects

 

 

 

 

 

0 vs 5 and 10 mM nitrate ** **
5 vs 10 mM nitrate‘ NS **
Amiben X nitrate interactions ’
0 vs 4 and 8 ppm amiben X 0 vs

5 and 10 mM N05 ** **
4 vs 8 ppm_amiben X 0 vs 5 and

10 mM N03 NS NS
0 vs 4 and 8 ppm amiben X 5 vs

10 mM NO' * **
4 vs 8 ppm amiben X 5 vs 10 mM

NOS NS NS

1

0 = no injury, 10 = complete kill.

*,**Significance at the 5 and 1% level respectively.

66

Table IV. Atrazine phytotoxicity to oats grown three weeks
in sand culture at three levels of nitrate as
measured by oat shoot injury ratings and dry.
weights

 

l -._W 1.,__n-

 

Injury rating1 Dry wt, mg/lO shootSI

 

mM Nitrate Atrazine, ppm Atrazine, ppm

 

 

 

 

 

 

 

 

Injury Dry wt

I
l
o 1 2 avg I o 1 2 avg , ea
0 1.4 5.7 7.6 4.9 136 64 61 87
5 0.0 9.0 9.9 6.3 245 62 62 123
10 0.0 9.3 9.7 6.3 317 80 61 153
avg 0.5 8.0 9.0 5.8 l 233 68 62 121
Planned Comparisons . _§ignificgnce

 

Atrazine effects

 

0 vs 1 and 2 ppm atrazine ** **
1 vs 2 ppm atrazine ** NS

Nitrate‘effects

0 vs 5 and 10 mM nitrate ** **
5 vs 10 mM nitrate NS **

Atrazine X nitrogen interactions

0 vs 1 and 2 ppm atr X 0 vs 5

 

 

 

and 10 mM N03 ** **
lvs2ppmatrX0vs5and

10 mM'NOS ** NS
0 vs 1 and 2 ppm atr X 5 vs

10 mM NO' NS **
1 vs 2 ppm atr x 5 vs 10 mM

N03 - NS NS

1

0 = no injury, 10 = complete kill.

*,**Significant at the 5 and 1% levels respectively.

67

Table V. Linuron phytotoxicity to oats grown three weeks
in sand culture at three levels of nitrate as
measured by oat shoot injury ratings and dry

 

 

 

 

 

 

     

     

 

   

weights
W ‘
Injury ratingl Dry wt, mg/10 shoots
mM Nitrate Linuron, ppm Linuron, ppm.
0 l 2 avg 0 1A 2 avg
0 1.1 3.0 4.3 2.8 168 74 70 104
5 0.1 4.6 6.8 3.9 247 73 71 131
10 0.1 5.3 7.4 4.3 299 75 64 146
238 74 68

 

 

 

       

 

Planned Comparisons Significance
Injury Dry w

Linuron effects.

 

0 vs 1 and 2 ppm linuron ** **
1 vs 2 ppm linuron ** NS

Nitrogen.effects

0 vs 5 and 10 mM nitrate ** **
5 vs 10 mM nitrate * NS

Linuron X nitrogen interactions

0 vs 1 and 2 ppm lin X 0 vs 5

 

 

 

 

and 10 mM N03 y - ** **
1 vs 2 ppm lin X 0 vs 5 and

10 mM NOS * NS
0 vs 1 ppm lin X 5 vs 10 mM

N03 * *
1 vs 2 ppm lin X 5 vs 10 mM

NOS . NS NS

1

0 = no injury, 10 = complete kill.

*,**Significant at the 5 and 1% levels respective-
ly. ‘

68

Table VI. Influence of source and rate of nitrogen and the
nutrient solution pH on amiben14-C absorption,
dpm/mg root, dry wt

IEW

Solution pH Nitrogen source and rate

 

Control Nitrate Ammonium

 

- 10 mM 50 mM lOmM 50 mM avg

 

 

4.0 687 423 310 1012 1424 771
5.0 651 438 304 578 540 502
6.0 400 288 195 495 452 366
7.0 172 168 243 324 362 254
8.0 172 198 185 179 110 169
avg 416 I 302 248 518 578 412

 

 

 

 

 

 

 

PLANNED COMPARISONS SIGNIFICANCE

Nitrogen effects

 

 

Control vs nitrogen NS
Nitrate vs ammonium **
10 mM N03 vs 50 mM NOS NS
10 mM NHitvs 50 mM NHdt NS
ph effects
Linear **
Quadradic **
Cubic NS

Nitrogen X pH interactionsl

 

NOS vs NH'TX pH linear **

10 vs so in NH4+x pH linear **

NOS vs NH4TX pH quadradic **

10 vs 50 mM NH4*X pH quadradic. . *
1

Only the significant interactions are given.

*f*=Significant at the 5 and 1% levels respectively;

69

 

 

 

 

Table VII. Buffering capacity of nutrient solutions solu-
tions with different sources and rates of
nitrogen

M

m1 acid or base to adjust pH/100
ml nutrient solution
Nitrogen source and rate1
pH adjusted
from: to: p

Control 10 mM 50 mM 10 mM 50 mM

N03 N03 NH 4+ 14114t

4.0 7.02 1.94 2.23 2.97 2.23 2.57
5.0 7.02 1.46 1.70 2.73 1.59 2.00
6.0 8.02 2.85 3.64 3.88 3.09 6.06.
7.0 5.03 1.82 1.67 3.64 1.77 2.34
8.0 6.03 3.18 3.42 2.32 2.62 5.08

 

 

 

 

 

 

1Solutions were complete for all other essential

elements.

2Adjusted with .05 N NaOH.

3

Adjusted with .05 H

2

SO .

 

70

 

aonz z e.w fies tongues eonesn a wuwe x w sow misc .833»;

1002 z _.o _E

.H enameh

 

O.N

o.¢

0.0

0.0

00.

 

Oh 00 On O¢ on ON 0—
I ! I J i‘ I [q
. N
w_w . xa .||\.
‘\
1
-
-
1
owe a _ a
-
— ._
u
-
\ 1
no... . mg a \\
.IIIIIIIIIIIIII|
Ill-I.IIIIIIIIIII- l

ON.

[46