bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Metabolic Inhibitors on Herbicide Movement in Plants
Authors: Taylor T. D. , Warren G. F.
Published: June 2019

Pretreatment of bean (Phaseolus vulgarisL.) petiole sections with one of several metabolic inhibitors greatly stimulated the movement of 3-amino-2,5-dichlorobenzoic acid (amiben) and (2,4-dichlorophenoxy)acetic acid (2,4-D). However, the movement of 3-amino-s-triazole (amitrole), 3-(3,4-dichlorophenyl)-1-methylurea (linuron), and isopropylm-chlorocarbanilate (chlorpropham) was stimulated only slightly or not at all. The basipetal movement of indole-3-acetic acid (IAA) was inhibited by concentrations of 2-sec-butyl-4,6-dinitrophenol (dinoseb) which stimulated respiration (5 × 10−7M to 5 × 10−8M). Acropetal movement was stimulated by dinoseb concentrations greater than 10−5M. Translocation of root-applied amiben and 2,4-D to the stems and leaves of whole plants of bean, squash (Curcurbita pepoL.), and cucumber (Cucumis sativusL.) was stimulated by dinoseb root applications only at concentrations which were highly injurious to the plants. Amiben, 2,4-D, and their metabolites were extracted from dinosebtreated and untreated tissues. The stem exudate from cucumber plants fed amiben and 2,4-D via the roots contained primarily the parent compounds, which indicates that the parent compounds are the primary components translocated through the xylem.
Effects of 2,4-D and Ioxynil on Seedling Fescue, Bluegrass, and Bentgrass
Authors: Adamson R. M. , Turley R. H.
Published: June 2019

Effects of the alkanolamine salt of (2,4-dichlorophenoxy) acetic acid (2,4-D) and sodium salt of 4-hydroxy-3,5-diiodobenzonitrile (ioxynil) upon seedlings of Chewings fescue (Festuca rubra var. commutata Gaud.), Park bluegrass (Poa pratensis L.), and Highland bentgrass (Agrostis tenuis Sibth.) were evaluated in growth room and field studies. In the former, injury to Park bluegrass from both 1 and 3 lb/A applications of 2,4-D was severe with pronounced but less marked effects on fescue and bentgrass. Results were similar from applications shortly after emergence and after clipping the grass. Negligible injury was caused by 1 lb/A of ioxynil. In the field, ioxynil gave better weed control than 2,4-D when applied at a seedling height of 1 inch. No injury was caused by ioxynil. Although 2,4-D reduced yields from early clippings, there was marked recovery, even at 3 lb/A. No treatments significantly affected plant stand.
Effect of Diallate and Triallate on Wild Oat and Wheat Cells
Authors: Banting J. D.
Published: June 2019

After 3 days or more germination in 5-(2,3-dichloroallyl) diisopropylthiocarbamate (diallate) or S-(2,3,3-trichloroallyl)diisopropylthiocarbamate (triallate) vapor, shoots and roots of wild oat (Avena fatua L.) and spring wheat (Triticum aestivum L.) were measured, sectioned, stained, and squashed for comparison of growth and mitotic activity. Shoot tissue of wild oat was damaged more readily than root tissue by diallate vapor. The meristematic tissue at the base of the first leaf was apparently more vulnerable than stem apex tissue since it exhibited more divisions and a greater number of abnormalities. The effect of triallate was similar but less pronounced. Shoot tissue of wheat also was more sensitive to diallate than root tissue. This was indicated by reduced mitotic activity and by shoot inhibition. Few abnormalities were observed in wheat even at high concentrations. Results were similar with triallate. Root and shoot measurements indicated that wheat was more tolerant to triallate than to diallate. Shoot inhibition occurred in both wild oat and wheat at concentrations that did not affect mitosis. Mitotic damage from the use of either diallate or triallate thus appeared to be of secondary importance, the major effect being on some phase of cell elongation or expansion.
Directed Applications of Herbicides in Irrigated Cotton
Authors: Hamilton K. C. , Arle H. F.
Published: June 2019

Directed applications of low rates of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), disodium methanearsonate (DSMA), monosodium methanearsonate (MSMA), 1,1′-dimethyl-4,4′-bipyridinium salts (paraquat), and 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne) controlled annual weeds in irrigated cotton (Gossypium hirsutumL.). Although the first applications of most herbicides caused temporary, localized foliage chlorosis or burning, cotton yields, fiber properties, and boll components were not affected. Early applications of DSMA followed by diuron selectively controlled annual weeds. When a herbicide was applied before planting, fewer postemergence applications were needed for weed control.
Invasion of Medusahead into the Great Basin
Authors: Young James A. , Evans Raymond A.
Published: June 2019

We characterized soil and vegetation assemblages, many of which are infested with medusahead (Taeniatherum asperum(Sim.) Nevski), on the margin of the Great Basin. Interpretations of these assemblages provide an index of the validity of the basic environmental unit of this ecosystem which can be manipulated through weed control and revegetation techniques. Vertisol (churning clay soils) sites with sparse native plant communities are more susceptible to medusahead invasion than more complex low sagebrush (Artemisia arbusculaNutt.) or low sagebrush-woodland communities on related clay soils. If the more complex communities are degraded to a low seral state, medusahead can invade and occupy the site. Wet meadows and burned coniferous forest sites at high elevations were the only sites where medusahead occurred on soils with textures other than clay. Big sagebrush (Artemisia tridentataNutt.) communities on medium to coarse textured soils were very resistant to medusahead invasion. The restriction of medusahead to certain sites controls the mechanism of invasion and interacts with the breeding system of the species to influence its evolution.
Uptake of Herbicides by Soybean Seed
Authors: Rieder G. , Buchholtz K. P. , Kust C. A.
Published: June 2019

The uptake of herbicides by soybean (Glycine max(L.) Merr.) seed from14C-labeled aqueous solutions of 3-amino-2,5-dichlorobenzoic acid (amiben), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron),S-ethyl dipropylthiocarbamate (EPTC), and isopropylm-chlorocarbanilate (chlorpropham) was determined by measuring reduction in the concentration of the herbicides in the soaking solution. There was a direct proportional relationship between uptake and concentration. Raising the temperature from 10 to 30 C increased uptake of herbicides. The greatest increase occurred from 10 to 20 C. After 48 hr at 30 C, 39% of the amiben, 61% of the atrazine, 65% of the EPTC, 83% of the linuron, and 92% of the chlorpropham in the original solution was absorbed by the seed. Uptake rates were similar in living and dead seed. Uptake was reversible with amiben but not with chlorpropham. Absorption of herbicides could not be associated with absorption of water except during the first few hours when the seed were rapidly imbibing water. Ratios of seed to solution herbicide concentrations all exceeded 1:1 after 48 hr and with chlorpropham, reached 68:1. The uptake of herbicides by seed was largely a physical process that required seed hydration, but herbicide uptake continued after water uptake ceased.
Effect of Root Temperature on Absorption and Translocation of Atrazine in Soybeans
Authors: Vostral H. J. , Buchholtz K. P. , Kust C. A.
Published: June 2019

Soybean (Glycine max(L.) Merr., var. Chippewa 64) plants were grown in culture solutions containing14C ring-labeled 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine). Culture solution temperatures were varied but ambient temperature about the shoots was constant. The amount of atrazine absorbed increased with increases in herbicide concentration, absorption time, and root temperature. Root temperature had more influence on atrazine accumulation in stems and leaves than in roots. Transpiration rates of atrazine-treated plants were reduced at least 50%.
The Metabolism of14C-Chlorbromuron in Corn and Cucumber
Authors: Nashed R. B. , Katz S. E. , Ilnicki R. D.
Published: June 2019

The metabolic fate of root-applied, carbonyl-labeled,14C-3-(3-chloro-4-bromophenyl)-1-methoxy-1-methylurea (hereinafter referred to as chlorbromuron) was investigated in tolerant corn (Zea maysL., var. N.J. 9) and susceptible cucumber (Cucurbita sativusL., var. Marketer) in a time-course study. The major metabolite found in corn shoots and roots was the nonphytotoxic 3-(3-chloro-4-bromophenyl)-1-methoxyurea. Evidence of “binding” was found in both shoots and roots of corn. No evidence was found for the metabolism of chlorbromuron in cucumber; however, some binding occurred in both shoots and roots.
EPTC Effects on Total Leaflet Fatty Acids and Hydrocarbons
Authors: Wilkinson R. E. , Hardcastle W. S.
Published: June 2019

Total foliar fatty acid and hydrocarbon content of sicklepod (Cassia obtusifoliaL.) treated with 0, 0.14, 0.28, 0.56, 1.12, 2.24, or 4.48 kg/haS-ethyl dipropylthiocarbamate (EPTC) was measured by gas-liquid chromatography. Total leaflet fatty acid content increased at sublethal rates of the herbicide, but qualitative composition of the fatty acids was not affected. Percent of long chain alkane (≥ C28) content decreased as EPTC application rates increased. Palmitic (23.9%), stearic (9.1%), oleic (3.8%), linoleic (13.6%), and linolenic (33.2%) acids accounted for 83.6% of the total leaflet fatty acid content of sicklepod. Leaflet cuticle thickness of upper and lower epidermal layers decreased 15 and 20%, respectively, as herbicide concentration increased.
Aberrations in Sugarbeet Roots as Induced by Trifluralin
Authors: Schweizer E. E.
Published: June 2019

Sixty percent of the roots of sugarbeets (Beta vulgarisL.) at harvest were aberrant in the zone of the hypocotyledonary neck when 0.84 kg/ha of α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) was sprayed primarily on the hypocotyledonary tissues of seedlings in the 10 to 12-leaf stage, compared to 7% when soil surrounded most of the hypocotyledonary tissues at the time of application. Trifluralin did not reduce the yield of roots or kilograms of sucrose per hectare in either treatment. Sucrose content and purity were lower, and total nitrogen was more than twice as high in sections of neck and root tissues where the aberrations were the most severe as compared to normal sections of neck and root tissues from the untreated plots. In the greenhouse, trifluralin inhibited the growth of primary and lateral roots in sugarbeet seedlings.
Uptake and Elimination of Simazine by Green Sunfish (Lepomis cyanellus Raf.)
Authors: Rodgers Charles A.
Published: June 2019

The uptake and release of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) by green sunfish (Lepomis cyanellus Raf.) were measured during a 3-week exposure to either non-labeled or symmetrically ring-labeled 14C-simazine. Exposure was by feeding (3 and 10 mg/kg body wt) or bath (1 and 3 ppm). To determine the retention of simazine, treated fish remaining after exposure and sampling were placed in fresh water for 4 weeks. This water was changed weekly. Fish in the bath absorb simazine in amounts directly proportional to the concentration in the water: i.e., 0.95 and 2.29 ppm total residue after 3 weeks exposure to 1.0 and 3.0 ppm, respectively. Little or no simazine was found in feed-exposed fish 72 hr after feeding. Almost all of the residue was in the viscera. No simazine residue was detected in fish from the water bath exposure after they had been in fresh water 7 days.
Interactions between Herbicidal Carbamates and Growth Regulators
Authors: James C. S. , Prendeville G. N. , Warren G. F. , Schreiber M. M.
Published: June 2019

Interactions between carbamate and growth regulator herbicides were antagonistic both in whole plants and in plant segments. When combinations of isopropylm-chlorocarbanilate (chlorpropham) and (2,4-dichlorophenoxy)acetic acid (2,4-D) were applied to the foliage of either redroot pigweed (Amaranthus retroflexusL.) or pale smartweed (Polygonum lapathifoliumL.), the severe twisting effects of 2,4-D were greatly reduced. This interaction did not involve differential movement or metabolism of either herbicide. The induced elongation of soybean hypocotyl sections by the three growth regulators 2,4-D, 3,6-dichloro-o-anisic acid (dicamba), and 4-amino-3,5,6-trichloropicolinic acid (picloram) was inhibited in the presence of either chlorpropham orS-ethyl dipropylthiocarbamate (EPTC). Similarly, curvature tests using soybean (Glycine max(L.) Merr.) hypocotyl sections showed the curvature induced by the growth regulators to be almost completely eliminated by the presence of the carbamates.
Influence of Weed Competition on Cotton
Authors: Buchanan Gale A. , Burns Earl R.
Published: June 2019

Cotton (Gossypium hirsutumL.) grown at two locations in Alabama from 1966 to 1968 produced maximum yields when kept free of annual weeds for approximately 8 weeks after emergence. Weed control for longer periods failed to increase yields. When initial weed control measures were delayed until 6 to 7 weeks after emergence at one location and 4 to 5 weeks at the other location, cotton was not injured. Prolonged weed competition past the critical periods usually resulted in drastic cotton yield reductions. Plant height and stem diameter of cotton were reduced by some of the weed competition treatments.
Effect of Picloram on Production and Quality of Seed in Several Grasses
Authors: Lee William O.
Published: June 2019

Twelve field trials were conducted in western Oregon during 1963 to 1966 to evaluate the effect of 4-amino-3,5,6-trichloropicolinic acid (picloram) on the seed production and seed quality of eight grass species. Seed production of creeping bentgrass (Agrostics palustris Huds., vars. Penncross and Seaside), Colonial bentgrass (Agrostis tenuis Sibth., var. Highland), perennial ryegrass (Lolium perenne L., var. Linn), Italian ryegrass (Lolium multiflorum Lam., var. Gulf), and tall fescue (Festuca arundinacea Schreb., var. Alta) treated with picloram was not statistically different from the untreated check. Seed production of Colonial bentgrass (Agrostis tenuis Sibth., var. Astoria) was reduced by picloram at rates of 1.0 and 1.5 lb/A. Seed production of Kentucky bluegrass (Poa pratensis L., var. Newport) was not statistically different from the untreated check when picloram was applied in October but was significantly lower than the check following some March treatments. Seed production of orchardgrass (Dactylis glomerata L., var. Potomac) and creeping red fescue (Festuca rubra L., var. Pennlawn) was reduced by most picloram treatments made either in October or March. Germination of the creeping red fescue seed was significantly reduced when picloram was applied at 2 lb/A in March. None of the treatments affected seedling development.
Effect of AMA on Synthesis and Utilization of Food Reserves in Purple Nutsedge
Authors: Duble R. L. , Holt E. C.
Published: June 2019

Chemical analyses for carbohydrates, fats, and protein and C14O2 tracer techniques were employed to study the influence of repeated applications of amine methylarsonate (hereinafter referred to as AMA) on food reserves in purple nutsedge (Cyperus rotundus L.). Purple nutsedge plants were grown under greenhouse conditions and treated at 3-week intervals with an aqueous solution of AMA. Chemical analyses suggested that repeated applications of AMA accelerated starch hydrolysis in tubers but had little effect on the fat and protein content. The disappearance of starch was correlated with an increase in the arsenic (hereinafter referred to as As) content of tubers following repeated applications. In leaf tissue, applications of AMA significantly reduced the sugar content and increased the protein content. Tracer studies on the rate of C14O2 fixation and evolution suggested that, in general, AMA-treated plants had a higher rate of utilization of the products of photosynthesis than untreated plants. Apparently, the carbohydrate fraction of food reserves was utilized in preference to fats and protein.
Additions to the Aliphatic Moiety of Chlorophenoxy Compounds
Authors: Linscott D. L. , Hagin R. D.
Published: June 2019

Ester derivatives of (2,4-dichlorophenoxy)acetic acid (2,4-D), 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB), 4-(2,4-dichlorophenoxy)crotonic acid, and 4-(2,4-dichlorophenoxy-β-hydroxy)butyric acid each were applied to alfalfa (Medicago sativaL.). Analysis of alfalfa extracts by gas chromatography and mass spectroscopy indicated 2-carbon additions to the aliphatic side chain of the applied chlorophenoxy compounds.
Influences of Soil Temperature on Reproduction of Curly Dock
Authors: Maun M. A. , Cavers P. B.
Published: June 2019

Plants of curly dock (Rumex crispus L.) were subjected to soil temperatures of 10, 15, 26, and 35 C in a growth chamber. A soil temperature of 10 C was most favorable for root growth and production of large seeds. The highest yields of seeds and fruit were obtained at 26 C. Significant reductions in seed and fruit production, wt per 100 seeds, plant height, and growth rate occurred at 35 C. The total germination of mature seeds was not affected by soil temperature, but the seeds ripened at 26 and 35 C germinated faster than those from the 10 and 15 C treatments.
Ammonium Nitrate and Phosphoric Acid Increase 2,4,5-T Absorption by Tree Leaves
Authors: Brady Homer A.
Published: June 2019

Addition of ammonium nitrate greatly increased the absorption of solutions of the isooctyl ester of (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) by sweetgum (Liquidambar styraciflua L.), post oak (Quercus stellata Wangenh.), red maple (Acer rubrum L.), and loblolly pine (Pinus taeda L.) leaves. Phosphoric acid alone and mixed with ammonium nitrate caused less increase. Ammonium nitrate speeded translocation of the herbicide in post oak but not in the other species.
Release of Herbicides by Soybean Roots in Culture Solutions
Authors: Moody K. , Kust C. A. , Buchholtz K. P.
Published: June 2019

The release of 3-amino-2,5-dichlorobenzoic acid (amiben), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), isopropylm-chlorocarbanilate (chlorpropham), S-ethyl dipropylthiocarbamate (EPTC), and 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) from excised soybean (Glycine max(L) Merr., var. Chippewa) roots following uptake of the herbicides from solutions for 1 hr was studied. Rates of release of herbicides into water were rapid with at least 30% of that taken up being released during the first 30 min. Herbicide X time and herbicide X concentration interactions were highly significant. In most instances, slow release continued for 4 hr, which was the duration of the experiment. Use of herbicide or nutrient solutions as release solutions did not significantly change the amounts of herbicides released. It was concluded that herbicide molecules released after 1 hr uptake were those that had diffused out from free space rather than those released from uptake or adsorptive sites.
Development of Axillary Buds from Johnsongrass Rhizomes
Authors: Beasley C. A.
Published: June 2019

Apical dominance, as maintained by above-ground foliage or individual rhizome apexes, is very marked in johnsongrass. (Sorghum halepense[L.] Pers.). Axillary bud development in single-node segments excised from individual rhizome pieces was least at the proximal end with increasing activity toward the distal end (apex end). Within serially excised, multi-node sections, axillary bud development was least at the proximal end and greatest at the distal end, and there was an overall increase in bud activity from proximal to distal ends of the rhizome pieces. This was true irrespective of whether the multi-node sections were cultured vertically (with buds oriented above the nodes) or were inverted (with buds oriented below the nodes). Lateral rhizomes exerted a dominating influence on the development of axillary buds from their parent rhizomes, as did the apical meristems of the parent rhizomes.
Atrazine Metabolism in Cotton as a Basis for Intermediate Tolerance
Authors: Shimabukuro R. H. , Swanson H. R.
Published: June 2019

Glanded and non-glanded isogenic lines of cotton [Gossypium hirsutumL., var. Empire 61(WR)] were treated with 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) to determine the significance of lysigeneous glands in the tolerance of atrazine by cotton. The presence of lysigeneous glands did not increase atrazine tolerance by cotton or decrease the inhibition of photosynthesis by the herbicide. Detoxication of atrazine by N-dealkylation occurred in both glanded and non-glanded cotton. No significant difference in atrazine metabolism was observed between the two lines. Atrazine metabolism may be a more important factor than the presence of lysigeneous glands in the intermediate tolerance of cotton to atrazine.
The Response of Canada Thistle Ecotypes to 2,4-D, Amitrole, and Intensive Cultivation
Authors: Hodgson J. M.
Published: June 2019

Root sections of Canada thistle (Cirsium arvense (L.) Scop.) ecotypes from different states were field planted at Bozeman, Montana. Canada thistle survival from repeated applications of (2,4-dichlorophenoxy)acetic acid (2,4-D), and 3-amino-1,2,4-triazole (amitrole) was markedly different. Ecotypes varied less markedly to cultivation although they differed significantly. Resistance of ecotypes to cultivation seemed related to adaptation to site while resistance to herbicides apparently was related to inherent physiological differences as well as to differences in adaptation.
Dissipation of Endothall and Effects on Aquatic Weeds and Fish
Authors: Yeo R. R.
Published: June 2019

Rates of dissipation, control of troublesome aquatic weeds, and toxicity to fish by the disodium and dipotassium salts of 7-oxabicyclo(2,2,1)-heptane-2,3-dicarboxylic acid (endothall) in farm reservoirs and in growth pools were studied from 1964 to 1967. In 4 out of 14 reservoir applications, initial concentrations of 0.3 to 1.4 ppm dissipated to near the limit of detection in 8 to 20 days. In the other 10, the dissipation ranged from 23 to an increase of 160% in 12 days. The average dissipation was 71%. In growth pools, initial concentrations of 0.5 to 4.0 ppm of endothal dissipated to 0.26 to 2.5 ppm in 12 days.
A Recirculating Spray System for Postemergence Weed Control in Row Crops
Authors: McWhorter C. G.
Published: June 2019

A recirculating sprayer was developed for applying herbicides in row crops to weeds taller than the crop. Herbicide solutions are applied through solid stream nozzles above and at right angles to the rows, so that a trap collects herbicide spray not deposited on weeds. Trapped solution is returned to the original spray tank by gravity flow. Good to excellent control of pigweed (Amaranthus spp.), cocklebur (Xanthium spp.), and sesbania (Sesbania spp.) was obtained with (2,4-dichlorophenoxy)acetic acid (2,4-D) while monosodium methanearsonate (MSMA) effectively controlled johnsongrass (Sorghum halepense (L.) Pers.). The better treatments increased the harvested yields of soybeans (Glycine max (L.) Merr., var. Lee) 6 to 8 bu/A when weed infestations were severe at time of treatment. Use of the sprayer permits treatment with herbicides normally considered too toxic to crops, and reduces costs through recovery of most of the herbicide solution that is not intercepted by weeds.
A History of Weed Control in the United States and Canada
Authors: Timmons F. L.
Published: June 2019

Available literature indicates that relatively few agricultural leaders and farmers became interested in weeds as a problem before 1200 A.D. or even 1500 A.D. For many centuries, weed control was mostly incidental to tillage for seedbed preparation and growing of crops and to growing and cutting or pasturing of thickly planted crops. Occasional references in literature previous to 1900 mentioned use of mechanical devices and a few inorganic herbicides specifically for weed control.

State weed laws directed at control of plant diseases were enacted during 1721 to 1766, but weed and seed laws involving weeds directly were not enacted until 100 to 200 years later. Only a few extension-type publications on weeds were issued in the United States and Canada between 1860 and 1900. There was a rapid increase in such publications after 1900. Research with inorganic chemicals as herbicides was begun in the 1890's in Europe and in a few states and provinces, and was increased at a rapid pace until the early 1940's. New developments in mechanical and biological control of weeds increased steadily during the same period. However, weed control remained a relatively minor phase of agronomy, botany, horticulture, agricultural engineering, and plant physiology until the early 1950's.

About 10 years after the discovery of (2,4-dichlorophenoxy)acetic acid (2,4-D) in 1942–1944, the much increased interest of scientists, federal and state governments, industrial companies, and the general public had begun to bear fruit. The word “weed” or “weeds” began to appear in the titles of college courses and extension specialists. Weed conferences had been organized in six regions of the United States and Canada and in 10 states.

The first meeting of the Weed Science Society of America was held in 1956 and Weed Science was adopted as its official journal. The number of herbicides in general use in the United States and Canada increased from 15 in 1940 to 25 in 1950, and to 100 in 1969. The total support for weed research in 1962 in the United States was six times that in 1950. The number of full-time research and extension workers or their equivalents in part-time workers had increased 20-fold and 13-fold, respectively, over the number in 1940.

The rate of advancement in the art and science of weed control has increased so rapidly that the progress in each of the recent brief periods 1941 to 1968, 1901 to 1940, and 1800 to 1900 is considered greater than that in all previous periods, beginning about 6000 B.C.
Bioassay of Herbicide Combinations with Rice
Authors: Hardcastle W. S. , Wilkinson R. E.
Published: June 2019

Rice (Oryza sativa L., var. Bluebonnet) bioassay was utilized to evaluate activity of several herbicide combinations at concentrations of each individual compound causing a 50% reduction in root length. Synergistic combinations were trichloroacetic acid (TCA) plus 1,1-dimethyl-3-phenylurea (fenuron); TCA plus 3-(p-chlorophenyl)-1,1-dimethylurea (monuron); TCA plus 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron); TCA plus 3-amino-s-triazole (amitrole); TCA plus 2,2-dichloropropionic acid (dalapon); and dalapon plus monuron. Additive results were obtained from combinations of TCA plus 1,2-dihydro-3,6-pyridazinedione (MH); dalapon plus fenuron; and dalapon plus diuron. MH and (2,4-dichlorophenoxy) acetic acid (2,4-D) exhibited antagonistic responses when combined with fenuron, monuron, diuron, dalapon, amitrole, and with each other. Antagonistic responses were obtained from combination of 2,4-D and TCA.
Control of Purple Nutsedge by Bensulide
Authors: Anderson W. Powell , Dunford Max P.
Published: June 2019

Soil incorporated into the tuber zone of purple nutsedge (Cyperus rotundusL.) at 1 to 9 kg/ha,O,O-diisopropyl phosphorodithioateS-esterwithN-(2-mercaptoethyl)benzenesulfonamide (bensulide) inhibited the growth of roots on plants developing from these tubers. The inhibitory effect was temporary and occurred only when bensulide was in intimate contact with the tubers and developing plants. When tubers were removed from bensulide-treated soil, washed, and replanted in untreated soil, root growth was normal. The production of shoots from tubers planted in bensulide-treated soil apparently was not affected, but shoot-growth was retarded when root growth was suppressed. When bensulide was incorporated into the upper 5-cm layer of soil, the shoots of nutsedge plants developing from tubers located below this layer grew through the treated soil with no adverse effect; the roots of these plants developed from basal bulbs below the layer of treated soil and were normal. Leaching bensulide-treated soil with 37.6 hectare-cm of water did not move enough bensulide into the soil to cause inhibitory growth effects on purple nutsedge.
Root and Foliar Absorption of Atrazine Applied Postemergence to Broadleaf Weeds
Authors: Thompson Lafayette , Slife F. W.
Published: June 2019

Results from both growth chamber and field experiments indicate that root absorption of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) applied postemergence to small broadleaf weeds is not a requisite for their control. Though broadleaf weeds absorb toxic quantities of atrazine from wet soil, they can be killed by foliar absorption alone because all of their meristems are exposed to a foliar spray. They are particularly sensitive when foliar penetration is enhanced by high relative humidity and wet foliage.
Development and Control of Honeyvine Milkweed
Authors: Coble H. D. , Slife F. W.
Published: June 2019

Seeds of honeyvine milkweed [Ampelamus albidus(Nutt.) Britt.] planted immediately after extraction from mature seed pods germinated 84% and after burial overwinter germinated 97%. Seedling emergence was limited to depths of less than 4 inches. Seedling roots developed adventitious buds capable of producing new shoots about 5 weeks after emergence. Preemergence and early postemergence treatments with 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) gave 100% control of seedlings in greenhouse experiments. Heavy natural infestations of honeyvine milkweed in corn (Zea maysL.) were controlled 95% with 2,4-(dichlorophenoxy)acetic acid (2,4-D) at 0.5 lb/A when treatments were made before the weed started climbing on corn stalks. Later treatments required higher rates of 2,4-D, the use of 2,4,5-(trichlorophenoxy)acetic acid (2,4,5-T), or the combination of 2,4-D plus 2,4,5-T for adequate control.
Herbicide and Phosphorus Influence on Root Absorption of Amiben and Atrazine
Authors: Doll Jerry D. , Penner Donald , Meggitt William F.
Published: June 2019

In the presence of relatively high but non-toxic levels of phosphate, the suppression of corn (Zea mays L.) or squash (Cucurbita maxima Duchesne) seedling growth in the dark by 3-amino-2,5-dichlorobenzoic acid (amiben) or 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) was enhanced. This effect was not due to increased uptake of either herbicide in the presence of the phosphate by roots of corn, squash, soybeans (Glycine max (L.) Merr.), or redroot pigweed (Amaranthus retroflexus L.). A proportional decrease in herbicide uptake with increasing herbicide concentration was most evident for amiben and atrazine uptake by the roots of soybean plants grown in the light.
Herbicide and Inorganic Phosphate Influence on Phytase in Seedlings
Authors: Penner Donald
Published: June 2019

Phytase activity increased 2 to 3 fold in barley (Hordeum vulgareL.), 6 fold in corn (Zea maysL.), and 12 fold in squash (Cucurbita maximaDuchesne) seedlings 2 days after the initiation of germination in the dark. Most of the phytase was found in the embryo of the seed, presumably in the cotyledon(s). Gibberellic acid and benzyladenine supplied during germination exerted only limited influence on the development of phytase in these seedlings. Of the herbicides studied, only sodium arsenite exerted an influence on phytase activityper sethat was of physiological significance. The presence of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 3-amino-2,5-dichlorobenzoic acid (amiben), 2-chloro-N-isopropylacetanilide (propachlor), 2,6-dichlorobenzonitrile (dichlobenil), or α,α,α-trifluoro-2,6-dinitro-N-N-dipropyl-p-toluidine (trifluralin) in the culture solution during germination partially inhibited the development of phytase activity. The herbicidal inhibition was enhanced if potassium phosphate at a non-inhibitory level also was present in the culture solution. The interaction of atrazine and amiben with phosphorus was not due to increased internal concentrations of inorganic phosphorus to a level inhibitory to the development of phytase activity.
CO2Compensation Concentration, Rate of Photosynthesis, and Carbonic Anhydrase Activity of Plants
Authors: Chen T. M. , Brown R. H. , Black C. C.
Published: June 2019

Leaves of a number of plant species were surveyed for their CO2compensation concentration which is one of the distinguishing characteristics used to classify plants on the basis of their photosynthetic capacity. Monocot genera with low CO2compensation values are mainly limited to tribes of Chlorideae, Paniceae, Andropogoneae, Tripsaceae, and a part of Festuceae in Gramineae. Major grain crops, except corn (Zea maysL.) and sorghum (Sorghum vulgarePers.), are primarily in the tribes of Hordeae, Aveneae, and Oryzeae, and have high CO2compensation concentrations. Seven genera of dicots with low CO2compensation occur in the four families of Amaranthaceae, Chenopodiaceae, Portulacaceae, and Euphorbiaceae. Major dicot crops are in the families Leguminosae and Malvaceae and have high CO2compensation points. Low CO2compensation concentration also is correlated with low carbonic anhydrase activity. Conversely, high CO2compensation concentration plants have a high carbonic anhydrase activity. Data on the influence of light intensity and temperature on the rate of photosynthetic CO2fixation in leaves from plants with high and low CO2compensation concentration indicate differential responses of photosynthesis to these environmental factors. The data are interpreted as supporting a hypothesis for competition by specific plants.
The Effects of Dichlobenil on Assimilate Transport in Purple Nutsedge
Authors: Akobundu I. Okezie , Bayer David E. , Leonard Oliver A.
Published: June 2019

Assimilate transport in purple nutsedge (Cyperus rotundusL.) was studied using autoradiographic technique. Results show the basic pattern of assimilate distribution was from areas of synthesis to areas of use or accumulation. The initial underground centers of high metabolic activity were replaced as these organs matured, by new centers of actively growing rhizomes, tubers, and roots. The planted tuber did not accumulate assimilates. Treatment of purple nutsedge plants with 2,6-dichlorobenzonitrile (dichlobenil) resulted in accumulation of assimilates in the tubers rather than in young underground tissues. Leaves of treated plants also accumulated labeled assimilate in excess of control plants. Assimilate accumulation in leaves of dichlobenil-treated plants resulted from the destruction of the phloem in the basal portions of the leaf-sheaths. An increase in tuber respiration accompanied an increase in accumulation of assimilates in dichlobenil treated tubers.
The Degradation Kinetics of an Ester of Silvex and the Persistence of Silvex in Water and Sediment
Authors: Bailey G. W. , Thruston A. D. , Pope J. D. , Cochrane D. R.
Published: June 2019

The degradation kinetics of propylene glycol butyl ether (hereafter referred to as PGBE) ester of 2-(2,4,5-trichlorophenoxy) propionic acid (silvex) and the persistence of silvex in water and sediment were studied under impounded conditions. PGBE ester of silvex was applied to the surface of three ponds at the rate of 9 kg/ha/A. Water and sediment samples were collected at 4, 12, 24, and 48 hr after treatment and were extracted for PGBE ester of silvex immediately after collection. The concentrations of PGBE ester of silvex and silvex present in the water and sediment samples were determined by gas chromatography. Physico-chemical and mineralogical characteristics of the sediment samples collected prior to treatment were determined. The hydrolysis of PGBE ester of silvex to silvex obeyed first order reaction kinetics, the specific reaction rate constants for the three ponds being 0.09 hr−1, 0.10 hr−1, and 0.14 hr−1. Fifty percent hydrolysis of PGBE ester of silvex occurred in 5 to 8 hr, 90% hydrolysis occurred in 16 to 24 hr, and 99% hydrolysis occurred in 33 to 49 hr. The concentration of silvex in water initially increased, but decreased to zero by the end of 3 weeks. Adsorption of both the PGBE ester of silvex and silvex appeared to occur on the sediment; essentially complete disappearance of both occurred by the fifth week following treatment. Under laboratory conditions, silvex adsorption by the sediments conformed to the Freundlich adsorption equation.
The Churches, the State and Modern War
Authors: J. F.
Published: June 2019

At its meeting in Uppsala, Sweden this summer, the World Council of Churches endorsed a principle that invites prolonged national discussion. With only a few negative votes, the 720 delegates adopted a resolution that endorses selective conscientious objection. The pertinent section from the 4,000 word statement entitled “Towards Justice and Peace in International Affairs” reads as follows:

“Protection of conscience demands that the churches should give spiritual care and support not only to those serving in armed forces but also to those who, especially in the light of the nature of modern warfare, object to participation in particular wars they feel bound in conscience to oppose, or who find themselves unable to bear arms or to enter the military service of their nations for reasons of conscience. Such support should include pressure to have the law changed where required.”
Aspects de la Civilisation Byzantine : Langue de culture et langue d'État à Byzance
Authors: Patlagean Evelyne
Published: June 2019

G. D. explique le rapport linguistique entre le latin et le grec en Orient comme le signe d'un rapport plus profond entre culture et pouvoir, dont le renversement accompagne les débuts de l'Empire de Byzance. L'Empire de Rome, capitale italienne de provinces hellénophones, c'était en effet selon lui, un pouvoir universel d'expression latine, soutenu par une culture universelle d'expression grecque.
Préhistoire africaine
Authors: Galy G.-R.
Published: June 2019

Cette plaquette est une suite de monographies sur les stations préhistoriques ou plus tardives de la région du rio Muni, dans la Guinée anciennement espagnole, à 2° de latitude N.

Certains niveaux archéologiques correspondent à une occupation fang, mais, sur les sites côtiers, abonde une céramique qui fut distribuée, dans tout l'Ouest africain, par la Compagnie hollandaise des Indes occidentales. Les gisements de l'Ile de Corisco, en particulier, traduisent des occupations successives, portugaise, hollandaise, allemande, anglaise et espagnole.
Nutrient Release From Permafrost Thaw Enhances CH4 Emissions From Arctic Tundra Wetlands
Authors: Lara Mark J. , Lin David H. , Andresen Christian , Lougheed Vanessa L. , Tweedie Craig E.
Published: June 2019

High‐latitude climate change has impacted vegetation productivity, composition, and distribution across tundra ecosystems. Over the past few decades in northern Alaska, emergent macrophytes have increased in cover and density, coincident with increased air and water temperature, active layer depth, and nutrient availability. Unraveling the covarying climate and environmental controls influencing long‐term change trajectories is paramount for advancing our predictive understanding of the causes and consequences of warming in permafrost ecosystems. Within a climate‐controlled carbon flux monitoring system, we evaluate the impact of elevated nutrient availability associated with degraded permafrost (high‐treatment) and maximum field observations (low‐treatment), on aquatic macrophyte growth and methane (CH4) emissions. Nine aquatic Arctophila fulva‐dominated tundra monoliths were extracted from tundra ponds near Utqiaġvik, Alaska, and placed in growth chambers that controlled ambient conditions (i.e., light, temperature, and water table), while measuring plant growth (periodically) and CH4 fluxes (continuously) for 12 weeks. Results indicate that high nutrient treatments similar to that released from permafrost thaw can increase macrophyte biomass and total CH4 emission by 54 and 64%, respectively. However, low treatments did not respond to fertilization. We estimate that permafrost thaw in tundra wetlands near Utqiaġvik have the potential to enhance regional CH4 efflux by 30%. This study demonstrates the sensitivity of arctic tundra wetland biogeochemistry to nutrient release from permafrost thaw and suggests the decadal‐scale expansion of A. fulva‐dominant aquatic plant communities, and increased CH4 emissions in the region were likely in response to thawing permafrost, potentially representing a novel case study of the permafrost carbon feedback to warming.
Seasonal and Interannual Variability of Areal Extent of the Gulf of Mexico Hypoxia from a Coupled Physical‐Biogeochemical Model: A New Implication for Management Practice
Authors: Feng Yang , DiMarco Steven F. , Balaguru Karthik , Xue Huijie
Published: June 2019

The extent of hypoxia on the Louisiana shelf has been measured during July since 1985. The measured area was assumed to represent the seasonal maximum each year and was related to the Mississippi‐Atchafalaya riverine May NO2+3 loading and May–June total nitrogen loading, for planning management strategies. In this study, we analyze 25 years of simulations from a coupled physical‐biogeochemical model. An empirical orthogonal function analysis of the hypoxia frequency reveals that the dominant pattern is east‐west, with the seasonal maximum occurring in June, July, or August. This indicates that the July hypoxic area may or may not always be the largest of the year. A simple linear regression model was constructed to examine the explained variance of hypoxia attributable to nutrients. Results reveal that the May NO2+3 (May–June total nitrogen) loading can explain 35% ± 7% (54% ± 7%) of the maximum cumulative hypoxic area in contrast to 22% ± 9% (48% ± 12%) of the July cumulative hypoxic area. Our results suggest that the current nitrogen loading reduction suggested by the Hypoxia Task Force 2013 is not sufficient to reduce the 5‐year moving average Gulf's hypoxic zone to less than 5,000 km2. A reduction of at least 66% (48%) of May NO2+3 (May–June total N) loading is needed when using July hypoxic area as the criterion, while a reduction of 77% (60%) of May NO2+3 (May–June total N) loading is needed when using maximum hypoxic area.
The Importance of CH4 Ebullition in Floodplain Fens
Authors: Stanley K. M. , Heppell C. M. , Belyea L. R. , Baird A. J. , Field R. H.
Published: June 2019

Uncertainty in estimates of CH4 emissions from peatlands arise, in part, due to difficulties in quantifying the importance of ebullition. This is a particular concern in temperate lowland floodplain fens in which total CH4 emissions to the atmosphere (often measured as the sum of diffusive and plant‐mediated fluxes) are known to be high, but few direct measurements of CH4 ebullition fluxes have been made. Our study quantified CH4 fluxes (diffusion, plant‐mediated, and ebullition) from two temperate floodplain fens under conservation management (Norfolk, UK) over 176 days using funnels and static chambers. CH4 ebullition was a major component (>38%) of total CH4 emissions over spring and summer. Seasonal variations in quantifiable CH4 ebullition fluxes were marked, covering six orders of magnitude (5 × 10−5 to 62 mg·CH4·m−2·hr−1). This seasonal variability in CH4 ebullition fluxes arose from changes in both bubble volume flux and bubble CH4 concentration, highlighting the importance of regular measurements of the latter for accurate assessment of CH4 ebullition using funnels. Soil temperature was the primary control on CH4 ebullition fluxes. Elevated water level was also associated with increased CH4 ebullition fluxes, with a distinct increase in CH4 ebullition flux when water level rose to within 10 cm of the peat surface. In contrast, CH4 ebullition flux decreased steadily with increasing plant cover (measured as vascular green area). Ebullition was both steady and episodic in nature, and drops in air pressure during the two‐day funnel deployments were associated with higher fluxes.
Damselfish in Distress?
Authors: Johnson-Groh Mara
Published: June 2019

Noise pollution may be changing how some species of fish develop.
Un-bee-lievable Geoscience Words in Record-Breaking Spelling Bee
Authors: Cartier Kimberly
Published: June 2019

Some spellers found that their Earth and space science words were honey sweet. Others were bee-trayed by stinging spellings.
Linking In Situ Photochemical Reflectance Index Measurements With Mangrove Carbon Dynamics in a Subtropical Coastal Wetland
Authors: Zhu Xudong , Song Lulu , Weng Qihao , Huang Guanmin
Published: June 2019

Photochemical reflectance index (PRI) has been found to be closely related with vegetation photosynthetic phenology in many ecosystems including boreal evergreen, but its ability to track carbon dynamics in low‐latitude evergreen mangrove ecosystems has rarely been assessed. To fill up this gap, this paper explored potential mangrove PRI‐carbon links and their environmental controls across temporal scales (diurnal and seasonal), based on 1‐year continuous high‐resolution (half‐hourly) time series measurements of spectral signals, eddy covariance carbon fluxes, and multiple environmental factors at a subtropical mangrove wetland of southeastern China. The diurnal variation of half‐hourly mangrove PRI, a U‐shaped changing pattern, was consistent with previous PRI studies on boreal evergreen, while the seasonal variation of daily mangrove PRI did not experience a hump‐shaped changing pattern as in boreal evergreen. Diurnal and seasonal mangrove PRI variations were significantly correlated with meteorological (radiation and vapor pressure deficit) and carbon‐related parameters (gross primary productivity, net ecosystem exchange, and light use efficiency), and the strength of diurnal PRI‐carbon correlations varied with meteorological factors with stronger correlations at enhanced radiation and vapor pressure deficit. Our results further indicated that physiology‐related PRI performed better than conventional structure‐related normalized difference vegetation index in tracking mangrove photosynthetic parameters. To the best of our knowledge, this is the first study to explore the link between high‐frequency PRI and carbon dynamics across temporal scales in natural mangrove ecosystems. The PRI‐carbon linkage confirmed by this study will improve our understanding of temporal variations in photosynthetic carbon dynamics in mangrove ecosystems.
The Impact of Peatland Restoration on Local Climate: Restoration of a Cool Humid Island
Authors: Worrall Fred , Boothroyd Ian M. , Gardner Rosie L. , Howden Nicholas J. K. , Burt Tim P. , Smith Richard , Mitchell Lucy , Kohler Tim , Gregg Ruth
Published: June 2019

Land use, land use change, and forestry (LULUCF) have been directly altering climate, and it has been proposed that such changes could mitigate anthropogenic climate warming brought about by increases in greenhouse gas emissions to the atmosphere. Changes due to LULUCF alter the Bowen ratio, surface roughness, and albedo and so directly change air temperatures. Previous studies have focused on changes in the area of forestry and have used space‐for‐time substitutions to assess the impact of LULUCF. This study considered 18 years of daytime land surface temperature over an area of actual land use change in comparison to its surrounding landscape and considered the restoration of a lowland peat bog: satellite land surface temperature data across 49, 1‐km2 grid squares with 20 on peatland and 29 on surrounding agricultural land on mineral soils from 2000 to 2017. The peatland squares were, until 2004, dug for horticultural peat and after 2004 were restored with revegetation of bare soil and restoration of natural water tables. Over the 18 years, the average annual daytime land surface temperature significantly decreased for six grid squares, five of which were on the restored peatland where land surface temperature decreased by 2 K. In 2000, before restoration, the peatland was 0.7 K warmer than the surrounding agricultural land on mineral soils but by 2016 was 0.5 K cooler. This study has shown that anthropogenic land use change could cool a landscape and that functioning peatlands could act as cool, humid islands within a landscape.