Absorption and translocation of the sodium salt of radioactive (2,4-dichlorophenoxy)acetic acid (2,4-D-2-14C) by wolftail (Carex cherokeensis Schwein) plants grown from rhizomes were enhanced by high relative humidity but were not affected by dimethyl sulfoxide (hereinafter referred to as DMSO). Greatest accumulation of 2,4-D-2-14C translocated from the treated leaf occurred, in the meristematic tissue. DMSO increased the herbicidal activity of the triethanolamine salt of 2,4-D alone, but 2,4-D plus DMSO was no more effective than 2,4-D plus X-77. When both DMSO and X-77 were added to the 2,4-D solution, the treatments were no more effective than when either additive alone was included.

Four greenhouse trials were conducted to determine the effects of various growth temperatures and soil moistures on dormancy of primary seed of selected strains from two wild oat (Avena fatua L. ssp. fatua (L.) Thell.) varieties. Both higher temperature and lower level of moisture decreased dormancy, temperature having a greater effect than level of soil moisture. The dormancy difference between seed produced on plants grown at 15.6 to 18.3 C in soil with approximately 75% or from 100 to 75% available moisture and at 25.3 to 28.4 C in soil with approximately 25% or from 100 to 25% available moisture ranged between 31 and 100%, dormancy tests being conducted 10 or 14 days after seed maturity. The magnitude of the difference in seed dormancy caused by conditions of growth was affected by strain and variety of wild oat, and by age of seed.

Experiments were conducted at Crawford and Kimball, Nebraska, during 1962, 1963, 1964, and 1965 to determine the effect of 13 herbicides on plains pricklypear (Opuntia polyacantha Haw.). The best control was obtained with 2-(2,4,5-trichlorophenoxy)propionic acid (silvex), 4-amino-3,5,6-trichloropicolinic acid (picloram), 3,6-dichloro-o-anisic acid (dicamba), and (2,4,5-trichlorophenoxy) acetic acid (2,4,5-T). Silvex and picloram were superior to dicamba and 2,4,5-T in controlling plains pricklypear, but picloram and dicamba injured the native grasses. Rotary hoeing plains pricklypear cladodes just prior to spraying improved herbicide performance. Simulated railing was not a consistent control measure. Evaluation of plains pricklypear control was made 1 and 2 years after herbicide application.

During 1967, field studies on the Holston River and in the laboratory produced evidence that excessive aquatic plant growths are not soley related to the presence of large amounts of nutrients in water. Factors contributing to growth were the amount of nutrients in sediments, water depth, and turbidity. Water depth and turbidity influence the amount of light which penetrates the water and is available for the growth of rooted plants.

The adsorption of seven s-triazines from aqueous solutions by organic soil colloids was determined at pH levels from 1.0 to 5.2. Maximum adsorption occurred at pH levels in the vicinity of the pKA values of the respective compounds. The amounts adsorbed were dependent upon the molecular structures of the compounds and the pH of the suspension and were, in order of decreasing adsorption, as follows: 2-methoxy-4,6-bis(diethylamino)-s-triazine (hereafter referred to as tetraetatone) = 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne) = 2-hydroxy-4,6-bis(isopropylamino)-s-triazine (hereafter referred to as hydroxypropazine) > 2-methoxy-4-diethylamino-6-ethylamino-s-triazine (hereafter referred to as trietatone) > 2-methoxy-4,6-bis(isopropylamino)-s-triazine (prometone) > 2-methoxy-4,6-bis(ethylamino-s-triazine (simetone) > 2-chloro-4,6-bis(isopropylamino-s-triazine (propazine). Approximately 52% of the prometone adsorbed by the organic matter was desorbed with two extractions of 0.1N NaCl. It was concluded that the adsorption of the s-triazines was due to complexing of the triazine molecules with functional groups on the organic colloids and/or adsorption of s-triazine cations by ion exchange forces.

Radioautographs showed that root uptake of 14C-methanearsonic acid (MAA-14C) by johnsongrass (Sorghum halepense (L.) Pers.) from nutrient solution was rapid and translocation into all portions of the plant occurred within 4 hr after treatment. Basipetal and acropetal translocation of foliar and stem-applied MAA-14C occurred in both johnsongrass and cotton (Gossypium hirsutum L., var. Rex smooth leaf), indicating that movement of the herbicide probably occurs in both phloem and xylem tissue. However, acropetal movement of MAA in both plants occurred at a higher rate than basipetal movement, and basipetal movement in cotton was not as rapid as in johnsongrass. Methanol extracts of MAA-14C johnsongrass were chromatographed. Radioactive spots with Rf values different from the MAA-14C standard were observed. Use of location reagents on the chromatographs suggested that MAA-14C may complex with either a sugar or organic acid or both. Amino acid fractions were prepared from methanol extracts of both plants. An MAA metabolite, with a positive reaction to ninhydrin, was located on chromatographs spotted with the amino acid fraction from johnsongrass but was not present in the cotton fraction. A comparison of Rf values suggests that the metabolite may be a combination of the MAA molecule with histidine or one of its analogues. Spectrophotometric determination showed a build-up of amino acids in MAA-treated johnsongrass but not in cotton. The increased levels of amino acids in johnsongrass suggest that the MAA metabolite may be blocking a protein synthesis pathway, or some other unknown biosynthetic pathway.

Land was prepared conventionally in early spring for the planting of small seeded legumes. Planting was delayed to allow emergence of weeds. We applied 1,1'-dimethyl-4,4'-bipyridinium salts (paraquat) and planted legumes immediately afterwards. Stage of weed growth, time of herbicide application, rate of chemical applied, and the methods of seeding were variables imposed. Paraquat (plus surfactant) applied at 1.1 and 2.2 kg/ha to emerged weeds prior to the seeding of legumes controlled quackgrass [Agropyron repens (L.) Beauv.] sufficiently to allow excellent establishment of alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.). A paraquat application delayed until yellow nutsedge (Cyperus esculentus L.) was at least 10 cm in height, followed by a disking, controlled the sedge sufficiently to allow legume establishment. For annual weed control, 0.3% kg/ha of paraquat was sufficient. Drilling as a method of seeding gave better legume stands than did surface-seeding techniques.

Root applications of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) at concentrations greater than 1.0 × 10-7M inhibited growth of parrotfeather (Myriophyllum brasiliense Camb.). Chromatographic analysis of exudate from detopped parrotfeather plants indicated that simazine was being tranlocated primarily as the intact molecule. A correlation coefficient of 0.985 was observed between the amount of simazine-14C removed from the treatment solution and transpiration during a 6-hr period. Absorption of simazine-14C by parrotfeather roots of intact plants was linear for the first 4 hr followed by a gradual decrease at the end of 6 hr. Simazine-14C at 1 and 2 hr after root applications was highest in the roots, intermediate in the lower part of the shoot, and lowest in the upper part of the shoot. After 192 hr, simazine-14C accumulated in the top of the shoot in a concentration higher than in the lower part of the shoot or the roots. A correlation coefficient of 0.988 was found between the amount of simazine-14C present in the tissue and the treatment concentration over a range of 1.2 × 10-6 to 5.0 × 10-6M.

The effect of stage of growth of field bindweed (Convolvulus arvensis L.) on absorption and translocation of 14C-labeled 2,4-D and picloram was studied. Three stages of growth investigated were s-week old seedlings, and 7-week old and 16-week old vegetatively propagated plants. One middle leaf of each plant was treated with either 14C-labeled (2,4-dichlorophenoxy)-acetic acid (2,4-D) or 4-amino-3,5,6-trichloropicolinic acid (picloram). Treated plants were harvested after 48 hr and assayed for radioactive 14C. The percent of 2,4-D applied which was absorbed by seedlings was less than that absorbed by adult plants. Picloram absorption was not different in seedlings and 7-week old adult plants, but the 16-week old adult plants absorbed more picloram than either the 5-week old seedlings or 7-week old adult plants. More picloram than 2,4-D was absorbed at all stages of growth. Translocation of both 2,4-D and picloram was greater in seedlings than in older plants. No difference was found in amounts of 2,4-D and picloram translocated by adult field bindweed plants. More 2,4-D than picloram was translocated by seedlings.

Widely varying weed densities that had been desiccated by freezing did not reduce combine efficiency (gathering plus threshing losses) in harvesting corn (Zea mays L., var. Nebraska 508), sorghum [Sorghum bicolor (L.) Moench, var. RS 610], or soybeans (Glycine max L., var. Ford). Average combine gathering losses with corn, sorghum, and soybeans were 2, 7, and 16%, respectively. Average threshing losses with the combine were less than 1% with corn and sorghum and less than 3% with soybeans. The high gathering losses in this study were due partly to delayed combining to allow the weeds to be desiccated by freezing temperatures.

The toxicity, leachability, and site of uptake of the herbicide 2-chloro-2',6'-diethyl-N-(methoxymethyl) acetanilide (hereinafter referred to as CP 50144) were studied in different soils. Two inches of water leached most of the compound to a soil depth of 2 to 3 inches, when applied at rates of 1 and 2 kg/ha. The inherent toxicity of CP 50144 to cotton (Gossypium hirsutum L., var. Acala 4-42) was studied in culture solution. The herbicide was most toxic to cotton when the entire root system of the crop was exposed to soil treated with CP 50144; reduction of weight of seedlings was accompanied by severe inhibition of root growth. On the other hand, only a slight reduction in growth rate was noticed when only the shoot zone of cotton was exposed to the herbicide.

The hydrogen bonding of 2,2-dichloropropionic acid (dalapon) to N-methylacetamide (NMA) as a model protein was studied using infrared spectra. Changes in the spectra indicated that the dalapon carboxyl-OH, hydrogen bonds significantly to the model amide carbonyl.

On Tifton loamy sand, N-1-naphthylphthalamic acid (naptalam) controlled weeds much better, and injured soybeans [Glycine max (L.) Merr.] much less, when mixed with 2-sec-butyl-4,6-dinitrophenol (dinoseb) and applied as a delayed preemergence treatment, than when it was applied alone immediately after planting. Differences attributable to either timing of application or to mixing with dinoseb were not as marked for 3-amino-2,5-dichlorobenzoic acid (amiben) as for naptalam. Neither amiben, naptalam, nor mixtures of these two herbicides with dinoseb adversely affected germination, weight per seed, or total oil and protein content of the harvested soybean seed.

The toxicity of 1,1'-dimethyl-4,4'-bipyridinium ion (paraquat) in soil can be related to the degree of bonding strength to the soil aggregates. Tightly bound material is unavailable to plants, while loosely bound material can be potentially available to plants. On the basis of growth of corn (Zea mays L., var. Golden Cross Bantam) and beans (Phaseolus vulgaris L., var. Idaho 1-11) in sand, loamy sand, loam, and muck treated with paraquat, it is concluded that planned and careful application would not lead to accumulation of lethal dosages in medium to heavy soils.

Herbicides applied shortly after wheat (Triticum aestivum L.) harvest combined with no tillage or with several minimum tillage treatments were compared with conventional tillage for weed control from wheat harvest 1 year through sorghum (Sorghum bicolor (L.) Moench) production the next year. Three lb/A of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) with no tillage did not completely control weeds, but over 4 years of sorghum grain yields on the atrazine-no tillage plots and on conventional tillage plots were not significantly different. One tillage either immediately before or immediately after application of 3 lb/A atrazine controlled essentially all weeds from wheat harvest until fall, but in some years grass weeds emerged in the spring. One pre-planting tillage or one cultivation after sorghum emergence reduced weed competition so that no additional weed control measures were needed. Sorghum yields from those plots were substantially above yields resulting from conventional tillage.

The phytotoxic monoterpenes, camphor, pulegone, and borneol, exhibit a marked synergistic action when used in combination. On a molar basis, these phytotoxic concentrations are enhanced from 40 to 100 times by using two compounds simultaneously. The toxicity of these compounds is about the same for radish (Raphanus sativus L.) and wheat (Triticum vulgare Vill.) but is less by an average of tenfold for oats (Avena sativa L.). When the compounds are used singly, they are from 3 to 12 times as effective in inhibiting root elongation as they are in inhibition of germination.

The effects of five herbicide and three in-the-row cultivation treatments on weed control and sugarbeet (Beta vulgaris L.) yield were studied at Mitchell and North Platte, Nebraska, during 1966 and 1967. Preplant soil incorporation treatments of 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) + N,N,dimethyltri-decylamine salt of 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid (endothall), and S-ethyl N-ethylthiocyclohexanecarbamate (cycloate), and postemergence application of pyrazon + 2,2-dichloropropionic acid (dalapon) resulted in better weed control and more sucrose per acre than S-propyl butylethylthiocarbamate (pebulate) applied preplant and soil-incorporated, and the untreated check treatment. Herbicide-treated plots kept weed-free by handweeding did not differ from the handweed check in sucrose production. Rotary hoeing improved weed control and increased sucrose yields as compared to flextine harrowing and the no in-the-row cultivation treatment.

Rates and magnitude for phytotoxic diminuation of 5-bromo-3-sec-butyl-6-methyluracil (bromacil) at 0.25, 0.5, and 1 ppm for oats (Avena sativa L.) and 1, 2, and 4 ppm for sorghum (Sorghum vulgare Pers.) plants were related to increased nitrogenous composition of organic and inorganic amendments with a Psammentic paleustalf, Eufaula sand. Soil isolates not inhibited by bromacil concentrations up to 2,000 ppm in defined broth media sans presynthesized growth factors included Aspergillus tamarii Kita, A. flavus Link ex Fries, A. oryzae (Ahlburg) Cohn, Penicillium funiculosum Thorn. P. brevicompactum Dierckx. Curvularia lunata (Wakker) Boedijn, Mucor pusillus Lindt, Trichoderma viride Persoon ex Fries, and Myrothecium verucaria Ditmar. A. niger van Tieghem was inhibited with bromacil levels less than 1500 ppm. This substituted uracil fungitoxicity was offset with increasing inorganic N levels to 500 ppm as NH4NO3 and/or 1,000 ppm of presynthesized growth factor additive as cyanocobalamin, yeast extract, and peptone. Bromacil levels to 100 ppm reduced nitrification temporarily for only 5 days in contrast to sustained inhibition of nitrification for 15 days by equivalent levels of 2-amino-4-chloro-6-methylpyrimidine (Toyo Koatsu AM).

In a 2-year study, kochia [Kochia scoparia (L.) Schrad.] competed with sugarbeets (Beta vulgaris L.) for various periods after emergence. Kochia then was removed and plants that emerged subsequently were controlled by hand-weeding. Yield of sugarbeet roots was reduced when kochia competed for more than 5 or 6 weeks. Kochia that competed with sugarbeets for the entire season reduced yields more than 95%. In another study, kochia was controlled by frequent hand-weeding for different periods after sugarbeet emergence. When kochia was controlled initially for 3 to 4 weeks, yield of sugarbeets was not reduced. Some kochia emerged following the 3 to 4 weeks of hand-weeding. However, competition from sugarbeets reduced the weight of this kochia at harvest by 59 and 92%.

The effect of 2,3,5-trichloro-4-pyridinol (pyriclor), as well as carbonyl cyanide m-chlorophenyl hydrazone, 2,4-dinitrophenol, and oligomycin, on oxygen uptake and oxidative phosphorylation was investigated with mitochondria isolated from hypocotyls of etiolated soybeans (Glycine max Merrill, var. Lee). Pyriclor inhibited both coupled and uncoupled reactions. This suggests that pyriclor either acts on a nonphosphorylating intermediate close to the electron carrier chain or with a component of the electron carrier chain, or both.