Previous research has shown that specific carotenoid pigments
function through oxidation-reduction reactions to protect chlorophyll
from photooxidation in the presence of reduced nicotinamide adenine
dinucleotide phosphate (NADP). The hypothesis that diuron (3-(3, 4-
d chloropheny1)-1, 1-dimethylurea) initiates phytotoxicity by inhibition
of NADPH synthesis was examined. All experiments were conducted
in...
Field, screenhouse, and laboratory experiments were conducted to
study weed interference in rice grown on hydromorphic soils at the
International Institute of Tropical Agriculture (IITA) at Ibadan, Nigeria.
Rice and weeds emerged at the same time, 1 week after planting.
Weed dry weight was significantly reduced when the crop was...
Apoplastic distribution patterns of atrazine [2-chloro-4-(ethylamino)-
6-(isopropylamino)-s-triazine], glyphosate [N-(phosphonomethyl)-
glycine], the naturally occurring apoplastic leaf solutes, and
the apoplastic dye PTS (trisodium 3-hydroxy-5,8,10-pyrenetrisulfonate)
were compared. Aliquots of sap were expressed from intact
sunflower leaves in a pressure chamber over intervals of 0.2 to 0.4
bars. Three distinct fractions were detected...
Tansy ragwort (Senecio jacobaea L. ) is a poisonous weed which
infests alfalfa fields in western Oregon. Studies were conducted to
evaluate the effectiveness of asulam (methyl sulfanilylcarbamate)for
control of tansy ragwort in alfalfa and to elucidate factors responsible
for its selectivity. In seven replicated field trials in 1973 and...
The behavior of metribuzin [4-amino-6-(1,1-
dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] and
ethyl-metribuzin (4-amino-6-(1,1-dimethylethyl)-3-
(ethylthio)-1,2,4-triazin-5(4H)-one] in soil was studied to
determine if differences in herbicide behavior in soil could
explain (a) the inconsistent herbicidal activity of these
chemicals and (b) the greater activity of metribuzin, as
compared to ethyl-metribuzin.
Metribuzin had higher activity than ethyl-metribuzin...
Tuber oatgrass (Arrhenatherum elatius (L.) Presl. var.
bulbosum (Willd.) Spenn.) is a perennial grass that often
becomes a weed problem in Western Oregon. Control efforts
using glyphosate often give unsatisfactory results. The
effects of several factors on development of tuber oatgrass
were investigated. Long days and cool temperatures (16/8h,
20/10C...
Cyperus esculentus L. var. esculentus is a serious weed
problem in northwest Spain. Long-term control from glyphosate and
other herbicides has been inconsistent. Field, greenhouse, and
laboratory studies were conducted on factors influencing the
activity of glyphosate on C. esculentus.
In field studies, glyphosate controlled foliage growth at most
growth...
Studies were initiated to determine the response of two common
groundsel biotypes (Senecio vulgaris L. ) to several s-triazine herbicides.
Herbicides tested were: 2-chloro-4,6-bis(ethylamino)-striazine
(simazine), 2-chloro-4-(ethylamino)-6-(isopropylamino)-
s-triazine (atrazine) 2-(sec-butylamino)-4-(ethylamino)-6-methoxys-
triazine (GS-14254), 2, 4-bis(isopropylamino)-6-methoxy-striazine
(prometone), 2-(tert-butylamino)-4-(ethylamino)-6-methylthio-
s-triazine (terbutryn), and 2, 4-bis(isopropylamino)-6-
methylthio-s-triazine (prometryne). One biotype was much more
susceptible than the...
Growth of individual goosegrass (Eleusine indica (L) Gaertn.) plants of
three dinitroaniline-herbicide resistant (R) and three susceptible (S) biotypes from
North Carolina, South Carolina, and Mississippi was analyzed in greenhouse
experiments. Leaf area and biomass measurements, including root, shoot,
above-ground, and total dry weights were similar among the biotypes studied....
Time-course growth chamber studies were conducted on little mallow
(Malva parviflora L.) to determine whether sublethal doses of lactofen
(1'-(carboethoxy)ethyl-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-
nitrobenzoate) would enhance uptake of glyphosate (N'-(phosphonomethyl)
glycine) by altering membrane permeability. Lactofen-induced membrane
peroxidation was determined by harvesting leaf discs, measuring stress
ethylene evolution, and recording increases in...
Diclofop (2- [4 -(2, 4-dichlorophenoxy)phenoxy] propanoic
acid), formulated as the methyl ester, selectively kills
barnyardgrass [Echinochloa crus -galli (L.) Beauv.] in several
crops when applied postemergence. Studies were conducted
to determine the effect of soil moisture, barnyardgrass age, and site of exposure on control of barnyardgrass with diclofop. Soil moisture...
Studies were conducted to verify the existence of IAA in wheat
seedlings and to determine the effect of (2-chloroethyl)-trimethyl-ammonium
chloride (CCC) on the IAA content of club wheat,
Triticum aestivum compactum, variety Omar. The shoots of CCC-treated
and untreated wheat plants were extracted with ethanol, the
plant extract purified, separated...
Investigations were made in the field, greenhouse, growth
chamber, and laboratory to: (a) observe the general activity of N-
(phosphonomethyl)glycine (glyphosate); (b) determine the extent of its
interaction with certain s-triazine herbicides; and (c) find an explanation
for such an interaction.
Greenhouse and growth chamber studies substantiated other
observations that...
Previous studies have shown loss of ethofumesate activity when
the herbicide was applied to dry soil (2% w/w moisture content) in
both field and greenhouse studies, even when rainfall or irrigation
was received within a few days. Laboratory studies were conducted to
determine the mechanism for this activity loss. Dry...
Living mulches are vegetative covers that can grow in association with row crops and may prevent soil erosion and suppress weeds. Crop reduction from association with the living mulch is a frequent problem with this cultural practice. The interference between a white clover (Trifolium repens L. "New Zealand") living mulch...
Eight postemergence herbicides were evaluated to determine
their influence on the incidence and severity of take-all disease
caused by the fungus Gaeumannomyces graminis var. tritici in winter
wheat. Mecoprop ((+)-2-(4-chloro-2-methylphenoxy)propanoic acid),
difenzoquat (1,2- dimethyl- 3,5- diphenyl -1H- pyrazolium), dinoseb amine
(amine salt of 2-(1-methylpropy1)-4,6-dinitrophenol), and diclofopmethyl
(methyl ester of (+)-2-[4-(2,4-dichlorophenoxy)...
The herbicide rate required to reduce growth by 50% (GR₅₀) of 11
cultivars of red fesue (Festuca rubra L. and F. rubra ssp. commutata)
and for four cultivars of bentgrass (Agrostis tenuis Sibth. and A.
stolonifera L. var. palustris) to sethoxydim (2-[1-(ethoxyimino)
butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one) was
determined in greenhouse and laboratory experiments....
Studies were conducted to determine the extent and nature of
sub-lethal effects of herbicides on plant growth. At least one
herbicide from each major chemical class of herbicides was evaluated
under greenhouse conditions. Oat plants were grown in sand
culture to eliminate soil interferences. Herbicides were applied
pre-emergence in nutrient...
After nearly 20 years of commercial use in orchards without
apparent tree injury in Oregon and Washington, 2,4-D [(2,4-dichlorophenoxy)
acetic acid] was reported in 1970 to cause injury to apple
and pear trees in Washington. In the early 1970's, there was widespread
concern among growers, researchers, and processors in the...
Glyphosate (N-(phosphonomethyl)glycine) is an effective
foliar-applied herbicide with broad-spectrum activity. Greenhouse
and laboratory experiments were conducted to determine the
importance of soil moisture, autoclaved soil, soil type, sphagnum
peat, soil pH, added phosphorus, and plant residues on crop
establishment and growth when glyphosate was applied before
emergence of the crop....
Greenhouse and growth chamber experiments were conducted with
the following objectives: (a) to study the effects of N-1-naphthylphthalamic
acid (naptalam) on shoot and tuber production, rhizome transformation,
and growth of yellow nutsedge (Cyperus esculentus L.) plants;
(b) to study the effects of N-phosphonomethyl glycine (glyphosate) on
nutsedge plants at different...
The influence of certain environmental and edaphic
factors on the germination and emergence of downy brome
(Bromus tectorum L.) was investigated in the laboratory. A
preliminary study was conducted to determine the osmotic
stability of mannitol and polyethylene glycol 20,000 (PEG)
solutions, which are commonly used to simulate water stress...
Studies were conducted to determine the nature of the interaction
between atrazine (2-chloro-4-ethylamino-6-isopropylaminos-
triazine) and magnesium on tomatoes. This interaction was
studied under two light regimes: continuous light and a 12-hour
photoperiod. Tomato plants were grown in sand cultures at three
levels of magnesium fertilization. Four weeks after planting,
atrazine...
A series of studies was conducted to determine the presence
of tobacco rattle virus (TRV), potato virus X (PVX), and other
viruses in wild plants and to evaluate the efficacy of the detection
methods; to characterize and purify an isolate of TRV; and
to study the interaction between TRV and...