Absorption and metabolism of 14C-3-amino-2,5-dichlorobenzoic acid (amiben) by six plant species were investigated for correlation with species sensitivity. Plant sensitivity was determined from amiben concentrations required to give 50% reduction of radicle extension of germinating seedlings and shoot dry weight of 10-day-old plants (I50). The I50 values showed that soybean (Glycine max (L.) Merr., squash (Cucurbita pepo L.), and ivyleaf morningglory (Ipomoea hederacea (L.) Jacq.) were tolerant, cucumber (Cucumis sativus L.) was intermediate and giant foxtail (Setaria faberii Herrm.) and velvetleaf (Abutilon theophrasti Medic.) were susceptible. Neither the amount of amiben absorbed, the transport to shoots, the concentration of radioactivity soluble in methanol, nor the distribution of radioactivity among amiben, N-(3-carboxy-2,5-dichlorophenyl)-glucosylamine (hereinafter referred to as N-glucosyl amiben), and an unidentified amiben conjugate (amiben-X) was associated with species sensitivity in 11-day-old plants. In seedling tissues, neither the concentration of methanol-soluble nor methanol-insoluble radioactivity correlated with sensitivity. Highly significant correlations between the log percentage composition of amiben, amiben-X, and N-glucosyl amiben in the methanol-soluble fraction of seedlings and log I50 for radical elongation were obtained; the correlations were negative for amiben and amiben-X but positive for N-glucosyl amiben.

In field trials, 2 gpa of oil enhanced the herbicidal activity of 3-amino-1,2,4-triazole (amitrole) and a mixture of amitrole + ammonium thiocyanate (hereinafter referred to as amitrole-T) on quackgrass (Agropyron repens (L.) Beauv.). None of the oils consistently increased the toxicity of other foliarly-applied herbicides. A paraffinic mineral oil enhanced the activity of amitrole on quackgrass to a greater degree than NH4SCN. The inclusion of a paraffinic mineral oil enhanced both the amount and the rate of 14C-amitrole and amitrole-T translocated from the treated leaf to the shoots and roots, this being more pronounced with amitrole (twelvefold) than with amitrole-T (twofold).

The metabolism of S-propyl-1-14C dipropylthiocarbamate (vernolate) was studied in soybean (Glycine max (L.) Merr., var. Lee) seedlings. The degradation of vernlate-14C to 14CO2 was dependent on the age of seedlings. Pretreatment with non-labeled vernolate resulted in a reduction of catabolic oxidation of vernolate-14C to 14CO2, a reduction of cellular incorporation, and a corresponding increase in ethanol soluble metabolites. Paper chromatographic separation of ethanol extracts revealed the presence of two major metabolites and two minor metabolites. The relative abundance of these metabolites was dependent on the age of seedlings and the time of exposure. Results of the time course study suggested the conversion of metabolite 3 to metabolite 4.

Uptake and translocation of 6,7-dihydrodipyrido[1,2-a:2′, 1′-c]pyrazidiinium salt (diquat) in elodea (Elodea canadensis Michx) was investigated by autoradiography and counting of plants treated with diquat-14C. Uptake initially was very rapid followed by a slower accumulation of diquat. Part of this uptake was reversible in water and rapidly reached a saturation value while the slower uptake was nonreversible. This reversibility of uptake appears to indicate an initial passive adsorption probably followed by accumulation. Slight basipetal and acropetal movement of diquat was demonstrated with accumulation in the nodes and axillary buds. Movement was unaffected by light versus dark treatments. Diquat injured treated and adjacent untreated shoots of elodea to almost the same extent. This transfer occurred whether or not the treated and untreated shoots were in contact.

Unicellular green algae were used as test organisms in experiments designed to provide an insight into the mode of action of 3-(m-trifluoromethylphenyl)-1,1-dimethylurea (fluometuron). Fluometuron suppressed the autotrophic growth of Chorella pyrenoidosa Chick (hereafter referred to as C. pyrenoidosa) and Euglena gracilis Klebs-strain ‘Z’ (hereafter referred to as Euglena) and the extent of inhibition was a function of herbicidal concentration. Euglena was less sensitive than C. pyrenoidosa. Treated cells contained less protein and chlorophyll than untreated cells, but the inhibitory effect of the herbicide on the algal growth was overcome when the organisms were grown heterotrophically. Fluometuron did not adversely influence respiration or the light-independent reactions that lead to the formation of chlorophyll or chloroplast precursors. It did interfere with the light-dependent or the greening process of chlorophyll synthesis and with photosynthetic oxygen evolution. Fluometuron appears to be selectively toxic to one or more light-mediated biochemical reactions required for the formation and function of photosynthetic pigments and organelles.

Five herbicides were applied postemergence to three Louisiana sugarcane (Saccharum officinarum L.) varieties. Nine or 12 lb/A of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) severely injured varieties C.P. 44-101 and C.P. 52-68, but variety N.Co. 310 was not affected. Conversely, N.Co. 310 was injured more by 2,2-dichloropropionic acid (dalapon) than the other varieties. Trichloroacetic acid (TCA) + 2,4-dichlorophenoxyacetic acid (2,4-D) at 10.6 plus 3 lb/A, reduced the yield of variety N.Co. 310 in one of 2 years only. This treatment had no adverse effect on yields of the other two varieties. All varieties appeared tolerant to 2,3,-6-trichlorophenylacetic acid (fenac) applied at 4 to 12 lb/A. Diuron injured a sensitive variety both when the foliage was sprayed and when only the ground at the base of the cane was sprayed. Plants treated in May were injured more than those treated 30 days earlier.

Highbush blueberries [Vaccinium australe (Small), var. Colville] grown on a Leon sand at Chatsworth, New Jersey were treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) and 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) each spring or each spring and fall from 1960 through 1966. The weed control obtained with diuron generally improved with continued use. At rates of simazine sufficient to achieve satisfactory control, the degree of weed control increased for the first 3 years and decreased the last 3 years. Diuron and simazine at rates sufficient to provide satisfactory weed control did not reduce the productivity of the blueberry plant. Palatability evaluations of off-flavor and sweetness of frozen blueberries, and objective measurements of pH and soluble solids, indicated that the diuron and simazine treatments did not affect any of these quality factors.

At rates as high as 40 lb/A, 1-(2-methylcyclohexyl)-3-phenylurea (siduron) did not reduce the growth of crabgrass (Digitaria spp.) seedlings although it was highly toxic to germinating seeds. Siduron placed at the 2-inch soil depth reduced root growth but not shoot growth of crabgrass. Barley (Hordeum vulgare L., var. Trail) roots, like crabgrass, were more affected than shoots. Carbonyl labeled siduron-14C was absorbed by both barley roots and shoots. Siduron-14C was translocated from roots to shoots but not from shoots to roots. Analysis of the extracts from plants treated at various times revealed that no metabolites of siduron-14C were present. Siduron must be present at the time of seed germination to effectively reduce plant growth.

Uptake and translocation of 14C label from S-2,3-dichloroallyl N,N-diisopropylthiolcarbamate (diallate) by roots and coleoptiles of wild oat (Avena fatua L.), wheat (Triticum aestivum L., var. Selkirk), barley (Hordeum vulgare L., var. Traill), and flax (Linum usitatissimum L., var. Bolley) were compared. The pattern of 14C label uptake and movement was similar in wild oat, barley, and wheat. However, translocation of the 14C label to the roots of wild oat was less than for barley. Although differential uptake and translocation per se did not appear to account for the selectivity of diallate for wild oat, some differences in translocation may have beep the result of metabolic breakdown products.

A study of herbicides to aid in establishing an Emerald zoysia (Zoysia japonica x Zoysia tenuifolia Willd. ex Trin.) sod was initiated in the summer of 1965. Eleven herbicides were applied to Emerald zoysia sod-plugs newly planted in Emory clay loam soil. All of the herbicides provided excellent premergence control of crabgrass (Digitaria spp.) and goosegrass (Eleusine indica (L.) Gaertn.) throughout the growing season following treatments. Both 1-(2-methylcyclohexyl)-3-phenylurea (siduron) and O-(2,4-dichlorophenyl) O-methyl isopropylphosphoramido-thioate (DMPA) caused either no observable injury or only slight injury, thus causing no apparent chemical inhibition of growth and resulting in a rapid rate of establishment of the turfgrass. But N-(2-mercaptoethyl)benzenesulfonamide S-(O,O-diisopropyl phosphorodithioate) (bensulide) and 2,6-di-tert-p-tolyl-methylcarbamate (terbutol) severely injured Emerald zoysia; they seriously retarded the growth of the zoysia and greatly inhibited ground cover. Herbicides which effectively eliminated weed competition but which greatly retarded the growth of the turfgrass were more detrimental to establishment rate than the actual competition from weeds. These results indicate that selecting a herbicide safe to the turfgrass is more important than choosing a herbicide which only gives good weed control. However, indications are that some herbicides do combine the two important factors of safety and excellent weed control.

The effects of residues of 16 herbicides used to control downy brome (Bromus tectorum L.) were studied in the greenhouse. Crested wheatgrass (Agropyron desertorum (Fisch. ex Link) Schult.) was planted in soils collected from field plots sprayed 1 to 4 years previously. At the rates used, some residues were lethal to crested wheatgrass seedlings, some caused severe malformation and/or herbage yield reduction, while others had no adverse effects.

Fifteen herbicidal treatments were evaluated for weed control effectiveness in peanut (Arachis hypogaea L.) culture at three locations in the peanut production area of eastern North Carolina during 1964 and 1965. Delayed preemergence treatments of 4,6-dinitro-o-sec-butylphenol (DNBP) alone and in combination with O-(2,4-dichlorophenyl) O-methyl isopropylphosphoroamidothioate (DMPA) were superior to conventional herbicidal and non-herbicidal control methods as were single and multiple incorporated treatments of S-propyl dipropylthiocarbamate (vernolate). A single postplant vernolate treatment incorporated 1 in deep provided weed control superior to that obtained for single preplant vernolate treatments incorporated 1 in or 3 in deep. Increased weed control and increased peanut safety were obtained from 2.5 lb/A of vernolate by incorporating treatments at 0, 7, and 14 days after planting rather than by using a single application. This multiple treatment was the optimum one evaluated and provided 53 days of control and required 10 hr/A of hoeing time.

The herbicides 2,6-dichlorobenzonitrile (dichlobenil), 7-oxabicyclo-(2.2.1)heptane-2,3-dicarboxylic acid (endothall), and 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) were examined for their influence on the activity and synthesis of proteolytic enzyme(s) in the cotyledons of squash (Cucurbita maxima Duchesne) seedlings. None of these herbicides affected the activity per se of the isolated proteolytic enzyme(s). The presence of the herbicides in the culture solution during germination caused different effects on the development of the proteolytic activity in the cotyledons for each of the three herbicides. Dichlobenil reduced the development of the activity in both the excised cotyledons and the cotyledons of intact embryos. This inhibition was overcome in part by the addition of benzyladenine to the culture solution. The inhibition of hormone synthesis or export by the embryonic axis caused by dichlobenil could explain the observed results. Endothall inhibited the development of the proteolytic activity in the cotyledons of the intact embryo treatment but had little effect on the excised cotyledons. Benzyladenine did not reverse this inhibition. The effect of endothall resembled the inhibition caused by actinomycin D, possibly indicating that endothall interfered with ribonucleic acid metabolism. Bromoxynil inhibited the proteolytic enzyme(s) development in the cotyledons of intact embryos but not in the excised cotyledons. This inhibition was partly overcome by benzyladenine. These results suggest that bromoxynil not only interferes with the hormonal control mechanism but also proteinase synthesis.

An experiment to investigate tillage practices for producing safflower (Carthamus tinctorius L.) and controlling weeds was conducted from 1963 to 1965. Three tillage intensities designated excessive, moderate, and minimum, depending on the number and kind of tillage operations performed prior to planting, were used. Three different tillage tools used as the primary implement in preparing the seedbed were sweep machine, oneway, and moldboard plow.

Excessive, moderate, and minimum tillage plots averaged 342, 374, and 413 lb/A of safflower and 72, 73, and 63 lb/A of weeds, respectively. The sweep machine plots produced the highest safflower yields and lowest weed yields at all intensities with the oneway and moldboard plow about the same. Yields produced from the best treatments in the experiment (minimum tillage with the sweep machine and seeding with the shoe drill) averaged approximately 300 lb/A more than commercial fields and weed control was effective.

The production of red triphenyl formazan (hereinafter referred to as TPF) from colorless 2,3,5-triphenyl tetrazolium chloride (hereinafter referred to as TTC) by living cells was used as a vitality indicator for examining the effects of 6,7-dihydrodipyrido[1,2-a:2′,1′-c] pyrazidiinium salt (diquat) in elodea (Elodea canadensis Michx) shoots at varying light intensities. Diquat at 10 ppmw completely killed the elodea in 6 hr at 183 ft-c and at almost the same rate at 13,000 ft-c due to light saturation near the lower level. Over 24 hr were required for this effect in the dark. Between 29 and 183 ft-c, TPF production varied inversely with the light intensity. A comparison is made with the destruction of chlorophyll by diquat.

We studied 4-amino-3,5,6-trichloropicolinic acid (picloram) alone and in combination with 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) or 1,1′-dimethyl-4,4′-bipyridinium salt (paraquat) for control of several greenhouse, nursery, and natural-grown, woody plant species. Picloram:paraquat combinations improved the control of some species such as yaupon (Ilex vomitoria Ait.) as compared to picloram alone at equal rates; but it had an antagonistic effect on huisache (Acacia farnesiana (L.) Willd.) and honey mesquite (Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell). Evaluation of picloram: 2,4,5-T combinations suggested that 2,4,5-T sometimes could be added in equal amounts to picloram to increase control or reduce picloram rates proportionately on huisache, honey mesquite and live oak (Quercus virginiana Mill.).

We studied the uptake and transport of 4-amino-3,5,6-trichloropicolinic acid (picloram) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) alone and in combination and in the presence of 1,1′-dimethyl-4,4′-bipyridinium salt (paraquat) by honey mesquite (Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell), huisache (Acacia farnesiana L. Willd., yaupon (Ilex vomitoria Ait.), and bean (Phaseolus vulgaris L.). Paraquat reduced transport of picloram by mesquite, huisache, and bean. Paraquat increased uptake of picloram by yaupon but did not affect transport. The uptake and transport of 2,4,5-T by mesquite decreased in the presence of picloram, but the uptake and transport of picloram increased in the presence of 2,4,5-T. Increasing ratios of 2,4,5-T:picloram up to 16:1 continued to increased uptake and transport of picloram; the inverse effect occurred for 2,4,5-T when picloram:2,4,5-T ratios were increased.

Purple nutsedge (Cyperus rotundus L.) and yellow nutsedge (Cyperus esculentus L.) tubers were stored at 5 C in soil treated at 0, 2, 3, 4, 6, 8, or 10 lb/A 2,6-dichlorobenzontrile (dichlobenil) for 2, 4, 6, 8, 10, or 12 weeks. Respiration of dormant tubers differed with species, unaffected by period of storage or dichlobenil concentration. Sprouting of untreated tubers decreased from 90% after 2 weeks storage to 43% after 12 weeks. Yellow nutsedge sprout production was uniform in time; purple nutsedge sprouting progressed to an 8-week high. Increased concentrations of dichlobenil progressively inhibited sprouting.

The persistence of 4-amino-3,5,6-trichloropicolinic acid (picloram) in soil was measured after varying periods of time up to 3 years with bioassay technique using sunflowers (Helianthus annuus L., var. Advent) as the indicator plant. Rates of application ranged from 0.5 to 48 oz/A on two soil types at Scott, Saskatchewan and two at Lacombe, Alberta. After 1 year, recovery ranged from 20 to 30% of the original application in the 0 to 9-inch depth in each soil not disturbed by tillage directly after application. Recovery of the herbicide applied at rates of 8 oz/A or higher in the fall declined to about 10% after 24 months and to 6% or less after 35 months for even the highest rates. Picloram activity generally was concentrated in the surface 6 inches, indicating limited downward movement due to water in each of the soils. However, there was a tendency toward greater downward movement in the soils having lower organic matter content.

Barley (Hordeum vulgare L. var. Trail) root growth was inhibited at lower concentrations of 1-(2-methylcyclohexyl)-3-phenylurea (siduron) than was shoot growth. The influence of siduron upon root metabolism was assessed with excised roots grown in 0 or 5 ppm siduron. More glucose-U-14C and leucine-U-14C were degraded to CO2 and less were incorporated into cell wall material and protein by roots grown in siduron. However, roots grown in siduron incorporated more adenine-8-14C into nucleic acids and degraded less adenine to CO2 than roots grown in water. It was suggested that siduron disrupted the normal nucleic acid metabolism of barley roots which was necessary for protein and cell wall synthesis.