The growth regulator, glyphosine [N,N-bis(phosphonomethyl)glycine], and other possible metabolites of glyphosine and glyphosate [N-(phosphonomethyl)glycine] [glycine, sarcosine, and aminomethylphosphonic acid (AMPA)] were tested individually (0.5 mM) or as a mixture (each at 0.5 mM) for their effects on growth, extractable phenylalanine ammonia-lyase (PAL) activity, hydroxyphenolic-compound production, chlorophyll and anthocyanin contents, and on soluble-protein levels in soybean [Glycine max (L.) Merr. ‘Hill’] seedlings. Most chemical treatments caused some inhibition of growth either on fresh weight accumulation or on root elongation in the light and dark over 72 h. Glyphosine was generally the most inhibitory and caused the greatest inhibition on axis dry-weight accumulation. Glyphosine significantly increased extractable PAL activity in axes of light- and dark-grown soybeans to a lesser extent than did glyphosate. AMPA had some inhibitory effects on extractable PAL activity whereas other compounds had little influence on the enzyme. These compounds had little effect on total soluble protein in axes or on soluble protein in PAL preparations from 12 to 72 h in light-or dark-grown seedlings. No in vitro effect of the chemicals on PAL activity was found at concentrations up to 0.5 mM. Hydroxyphenolic compound levels increased within 24 to 72 h (per gram fresh weight basis) in light- or dark-grown soybean axes treated with glyphosine, AMPA, or a metabolite mixture (AMPA, sarcosine, and glycine). Anthocyanin content was decreased by glyphosate and to a lesser extent by glyphosine, but was increased by AMPA and the mixture. Glyphosate significantly increased the chlorophyll a/b ratio and decreased total chlorophyll, but glyphosine decreased the chlorophyll content to a lesser degree.

Seeds of five yellow foxtail [Setaria lutescens (Weigel) Hubb.] biotypes, collected from Connecticut, Iowa, Massachusetts, Pennsylvania and California, were tested for dormancy and germination characteristics. Seeds of the California biotypes, while dormant at time of dispersal, germinated readily following a 4-month after-ripening period in dry storage. California biotype seeds did not require stratification. The eastern biotypes also showed high initial dormancy. Prolonged dry storage (16 months) or stratification overcame this dormancy to varying degrees. All five biotypes germinated over the range of 15 to 35 C, but the California biotype exhibited much higher germination at 35 C than any eastern biotype. The California biotype germinated more rapidly, by 1 to 3 days, at any given temperature than the eastern biotypes. These differences in dormancy and germination requirements between the five biotypes are considered as evidence to support a hypothesis of genetically controlled, physiological differences between geographically separated biotypes.

Buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone} may be useful for selective weed control in corn (Zea mays L.) but injures corn seedlings at high rates. Greenhouse studies were initiated to test potential antidotes for buthidazole injury to corn seedlings. NA (1,8-naphthalic anhydride) and CDAA (N,N-diallyl-2-chloroacetamide) were the most effective of six chemicals evaluated. A ratio of 1:3 (buthidazole: CDAA) appeared to be optimal for the protection effect. CDAA appeared to be more effective than NA. Since both CDAA and NA offered limited protection but R-25788 did not, this action appears to be through a different mechanism than the one proposed for the thiocarbamate or acetanilide herbicides. The other chemicals tested were R-25788 (2,2-dichloro-N,N-diallylacetamide), R-29148 (2,2-dimethyl-5-methyl-dichloroace-tyloxazolidine), carboxin (2,3-dihydro-5-carboxanilido-6-methyl-1,4-oxanthiin) and gibberellin (GA3). Seven herbicides, members of the acetanilide, thiocarbamate, and dinitroaniline groups, were also tested for their antagonistic interactions but none offered protection.

Responses of the vegetative growth of cogongrass [Imperata cylindrica (L.) Beauv.] to temperature and photoperiod were studied in plants grown from stem and rhizome propagules collected from plants originating at four locations in southern Alabama and Mississippi. The plants were grown in four controlled-environment chambers with day/night temperature regimes of 23/17 C and 29/23 C, photoperiods of 12 h and 16 h, and photosynthetic photon flux densities (PPFD) of 650 μE(einsteins)m−2s−1. After 87 days, heights, leaf areas, total dry weights, rhizome numbers, and rhizome dry weights were significantly greater in plants grown at 29/23 C than at 23/17 C. Total dry weights, rhizome numbers, and rhizome dry weights were greater at the 16-h photoperiod than at 12 h. Plants grown from propagules from the McNeil, Mississippi population, which originated from an introduction from the Philippines, were significantly smaller than plants grown from propagules collected from populations thought to have originated from an introduction of cogongrass from Japan. Mathematical analysis of the growth data showed that the observed differences in dry matter production were more closely related to differences in leaf area duration than to differences in net assimilation rate.

When glyphosate [N-(phosphonomethyl)glycine] was fed through the transpiration stream of excised bean (Phaseolus vulgaris L. ‘Red Kidney’) shoots, it was readily absorbed and transported to the leaves where it inhibited transpiration. Maximum inhibition (40 to 50%) resulted from tissue concentrations of 50 to 3000 nmoles glyphosate/g fresh weight, while transpiration was significantly inhibited (20%) by as little as 15 nmoles/g fresh weight. A combination of 5 X 10-4M tyrosine (Tyr) and 5 x 10-4M phenylalanine (Phe) supplied continuously through the transpiration stream prevented the inhibition of transpiration by glyphosate during the course of 8-h experiments. Tyrosine (10-3M) alone delayed the transpiration response to glyphosate by 2 to 3 h but 10-3M Phe alone did not affect the inhibition by glyphosate. Levels of endogenous Tyr and Phe were about 50% lower in glyphosate-treated leaves than in the controls 6 h after treatment.

Applications of 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 1.1 kg/ha at the start of each growing season severely damaged established alfalfa (Medicago sativa L. ‘Beaver’) and reduced seed yield 32% over a 4-yr period. Dandelion (Taraxacum officinale Weber) populations were reduced but perennial sowthistle (Sonchus arvensis L.) increased in frequency. Dichlobenil (2,6-dichlorobenzonitrile) applied at 2.1 kg/ha controlled both dandelion and perennial sowthistle. Alfalfa was damaged initially but rapid recovery resulted in an increase in seed yield in 2 yr out of 4. Terbacil (3-tert-butyl-5-chloro-6-methyluracil) applied at 1.1 kg/ha also controlled dandelion and perennial sowthistle. No alfalfa damage was evident and seed yields were increased 34% over a 3-yr period. Seed yield increased 30% where asulam (methyl sulfanilylcarbamate) was applied at 4.5 kg/ha, but there was no visible effect on the growth of either alfalfa or weeds. Simazine [2-chloro-4,6-bis (ethylamino)-s-triazine], propham (isopropyl carbanilate) + PCMC (p-chlorophenyl-N-methyl carbamate), pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide], and diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], did not affect alfalfa seed production significantly, although simazine and diuron did reduce dandelion populations.

The effects of soil temperature, moisture, and herbicide concentration on the rate of degradation of dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) were measured in clay loam and sandy loam in the laboratory. In sandy loam, the rate of degradation increased with increasing temperature. In clay loam, the rate of degradation increased from 10 to 30 C and decreased at 40 C. Soil moisture content influenced the rate of degradation in the following order: 22>11>>2.2% (air-dry) for clay loam and 12.0 = 6.0>>0.5% (air-dry) for sandy loam. First-order half-lives ranged from 3.2 at 30 C to 47 weeks at 10 C in clay loam, and 2.3 at 40 C to 31 weeks at 10 C in sandy loam. Applications in 2 yr did not cause buildup of dinitramine in the field. A mathematical model was used in an attempt to correlate laboratory and field data.

Peanuts [Arachis hypogaea (L.) ‘Florunner’], infested with sicklepod (Cassia obtusifolia L.) and Florida beggarweed [Desmodium tortuosum (Sw.) DC.] were grown in 20.3-, 40.6-, and 81.2-cm rows on Dothan sandy loam at Headland, Alabama, and on Greenville sandy clay loam at Plains, Georgia. In-row seeding rates were equal, regardless of row width. Peanuts were maintained free of sicklepod and Florida beggarweed for 0, 2, and 5 weeks after emergence or throughout the season. In either the absence or presence of weeds, peanut yields generally increased with decreasing row width. Quality of peanuts was not adversely affected; in fact, desirable attributes such as percent sound mature kernels (SMK's) were sometimes increased as the row width decreased. Weed growth with close rows was much less than with standard 81.2-cm rows. Although yields of peanuts were lower with increasing time of weed competition, the influence of row spacing on competitiveness of the peanut canopy remained relatively constant on both soil types. Generally, weeds from either seeded or natural stands produced equivalent competitive results.

Under greenhouse conditions, postemergence herbicide effectiveness was greater when barnyardgrass [Echinochloa crus-galli (L.) Beauv.] plants were 5-or 10-cm tall as compared to 15-or 20-cm tall. Absorption of 14C-glyphosate [N-(phosphonomethyl)glycine] decreased from 58% of applied to 47% as plant height increased from 5 to 15 cm, and an additional reduction (to 32% of applied at 5 cm) occurred when terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine] was added to glyphosate. Translocation of 14C-glyphosate was reduced in older plants or when terbutryn was added to glyphosate. Water stress studies included soil moisture levels of 10, 20, 30, and 40% moisture (PW). Herbicide treatments were less effective at soil moisture levels below field capacity (30 PW). When soil moisture was 10 PW (-37 bar) absorption of 14C-glyphosate was greatly reduced in plants treated at both 7.5-and 15-cm heights with or without terbutryn. At 10 PW only 15 to 20% of applied 14C was absorbed whereas at 40 PW, absorption was over 45% and 62% with and without terbutryn, respectively. The addition of terbutryn to glyphosate resulted in decreased translocation for all soil moisture levels except the 20 PW treatment at the 15-cm height. Translocation of 14C was greatly reduced for plants in soils at 10 PW for both herbicide treatments.

Field trials conducted in the three major peppermint-producing regions of Oregon showed that repeated applications of bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] at 2.2 kg/ha controlled Canada thistle [Cirsium arvense (L.) Scop.] in peppermint (Mentha piperita L.) selectively. Repeat applications of 2.2 kg/ha controlled Canada thistle better than single applications of 3.4, 4.5, or 6.7 kg/ha. Late May or June applications were more effective than early May applications. The number of Canada thistle shoots was reduced 82% 10 months after repeat applications but had almost returned to the original number 22 months after application. Basipetal translocation of bentazon was demonstrated by observing bentazon injury symptoms on untreated Canada thistle shoots which were attached by a root to bentazon-treated shoots.

A field experiment of 2 yr duration at two locations was conducted to determine the effectiveness of glyphosate [N-(phosphonomethyl)glycine] and vernolate (S-propyl dipropylthiocarbamate) as single or combination treatments for quackgrass [Agropyron repens (L.) Beauv.] control in a soybean [Glycine max (L.) Merr.]-corn [Zea mays (L.)] rotation. Vernolate applied preplant incorporated at 3.36 kg/ha gave 30 to 58% and 28 to 34% quackgrass control at the end of the first and second growing seasons, respectively. Spring applications of glyphosate at 1.12 and 1.68 kg/ha before plowing gave 53 to 90% quackgrass control at the end of the second growing season. Glyphosate at 1.12 and 1.68 kg/ha followed by vernolate preplant incorporated at 3.36 kg/ha gave 85 to 99% quackgrass control at the end of the second growing season. Although vernolate did not provide effective long term quackgrass control, it did effectively augment quackgrass control when applied as a sequential treatment to glyphosate applied at 0.56 or 1.12 kg/ha.

A 4-yr field test was initiated in 1975 to determine susceptibility of a natural infestation of six morningglory species to herbicides which can be applied to the soil and foliage in soybeans [Glycine max (L.) Merr.]. The species studied were pitted morningglory (Ipomoea lacunosa L.), entireleaf morningglory [Ipomoea hederacea (L.) Jacq. var. integriuscula], ivyleaf morningglory [Ipomoea hederacea (L.) Jacq.], purple moonflower [Ipomoea muricata (L.) Jacq.], palmleaf morningglory [Ipomoea wrightii (Gray)], and small flower morningglory [Jacquemontia tamnifolia (L.) Griseb.]. Control with herbicides applied preplant incorporated and preemergence was dependent on morningglory species and on rainfall to allow plant uptake of the herbicide. Herbicides applied to the soil were not as effective as those applied postemergence. Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] gave the best and longest lasting preemergence control, averaging 79% control for all species. Preemergence control with metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] was dependent on species, with 84% control of small flower morningglory and only 26% for ivyleaf and 18% for entireleaf morningglory. At V2 (one trifoliolate) and V5 stages of soybean growth, acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} at 0.56 kg/ha applied over-the-top and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] at 0.28 kg/ha applied post-directed gave 90 and 92% control of all species, respectively. Most effective were repeated post-directed applications at V5 and V7 stages of soybean growth. Metribuzin + 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] (99%), linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] + 2,4-DB (98%), 2,4-DB (95%), and paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) + 2,4-DB (93%) provided excellent control regardless of the morningglory species.

The effects of ethylene upon germination of common cocklebur (Xanthium pensylvanicum Wallr.) and redroot pigweed (Amaranthus retroflexus L.) seeds were studied. In laboratory tests with seeds in sealed flasks in the dark, 10 μl/L ethylene increased germination of redroot pigweed seeds from 7% to 52% at 30 C, and increased germination of large and small common cocklebur seeds from 30% and 0% to 100% and 90% respectively, at 25 C. At least 12 h of exposure to ethylene was necessary for appreciable stimulation of germination. In growth chamber studies with known numbers of seeds in pots of soil, ethylene at 11 kg/ha was injected into the soil, and the pots were enclosed in plastic bags for 24 h. One such injection at 2 weeks after planting, and successive injections at 2, 3, and 4 weeks, significantly increased redroot pigweed seedling emergence, and significantly decreased the numbers of dormant, viable seeds remaining in the soil. When pots were not enclosed, injections did not significantly effect redroot pigweed seeds, but significantly increased common cocklebur seedling emergence and decreased the number of viable common cocklebur seeds remaining in the soil.

The effects of varying concentrations and duration of alachlor [2-chloro-2′,6′diethyl-N-(methoxymethyl)acetanilide] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] treatment on root growth, cell division, and cell enlargement were studied. Peas (Pisum sativum L. ‘Alaska’) and oats (Avena sativa L. ‘Victory’) were treated from 0 to 48 h with concentrations ranging from 1 × 10-8 to 1 × 10-3 M of each herbicide. After 48 h, average growth rates were significantly inhibited at concentrations of 1 × 10-7 M alachlor and 5 × 10−8 M metolachlor, and 5 × 10−7 M alachlor and 1 × 10-6 M metolachlor for peas and oats, respectively. When growth inhibitions were examined across time at concentrations greater than these, the degree of growth inhibition was a function of both concentration and duration of treatment. Often the greatest decrease in growth occurred between 0 and 12 h. Mitotic indices of root tip squashes from pea roots and paraffin sections from oat roots were determined. There was a significant reduction in the mitotic indices of pea roots treated for 48 h with 5 × 10−6 M alachlor or 1 × 10-5 M metolachlor. After a 30-h treatment, the mitotic indices of oat roots were significantly reduced by 1 × 10−7 M metolachlor and 1 × 10−6 M alachlor. Significant inhibition of elongation of etiolated oat coleoptiles were observed at 5 × 10−6 M alachlor (27%) and 5 × 10−5 M metolachlor (30%). Inhibition of pea hypocotyl elongation did not occur at concentrations below 5 × 10−4 M. It was concluded that the growth inhibition of plants caused by alachlor and metolachlor results from both an inhibition of cell division and cell enlargement.

Residue of picloram (4-amino-3,5,6-trichloropicolinic acid) aerially sprayed onto a central Arizona chaparral stand was markedly reduced in the surface 7.6 cm of soil from a fall burn conducted 5 weeks later. Brush control was also reduced.

The relationship between herbicide injury and soybean [Glycine max (L.) Merr. ‘Amsoy 71’] yield response was studied under weed free conditions at three locations. Reduced crop vigor at early growth stages was not an adequate indicator of yield response. Yield reduction was greater when soybean stand was reduced by herbicides than when stand was reduced to the same level by hand thinning. Yield response was a function of the degree and persistence of crop vigor reduction in a reduced stand of soybeans.

Several environmental and edaphic factors were monitored to determine their association with tolerance of seeded tomatoes (Lycopersicon esculentum Mill.) to diphenamid (N,N-dimethyl-2,2-diphenylacetamide). Injury increased with increasing soil pH and reduced temperature within 7 days of seeding in both field and growth chamber tests. The application of soluble fertilizer and diphenamid at planting acted synergistically to increase tomato injury. Prior to emergence of the tomato seedlings, 14C-diphenamid uptake was slight but increased with higher temperatures, while growth was inhibited at both low and high temperatures. Uptake and metabolism of 14C-diphenamid by plants in the cotyledon stage was not greatly affected by temperature or pH; however, translocation from the root to the shoot was reduced under low temperatures and high pH. These differences in translocation paralleled reported differences between tolerant and susceptible species, and may account for the increased diphenamid injury to tomatoes grown under stress conditions.

The single-celled green alga Chlamydomonas eugametos was found to be well suited for detecting growth inhibitor activity of chemicals. Tests consisted of solubilizing technical grade compounds in 20-ml aliquots of a 1 × 105 cells/ml zoospore culture. Commercially available growth inhibitor herbicides significantly inhibited synchronous cell population increases within 48 h at concentrations ranging from 1 × 10−4 to 1 × 10−7M. Examples of compounds that inhibited Chlamydomonas more than 50% were butylate (S-ethyl diisobutylthiocarbamate) and diallate [S-(2,3-dichloroallyl)diisopropylthiocarbamate] at 1 × 10−4M, CDEC [2 chloroallyl diethyldithiocarbamate] and propham (isopropyl carbanilate) at 1 × 10−5M, alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] and trifluralin [α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine] at 1 × 10−6 M, and bifenox [methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate] at 1 × 10−7M. Ethanol, dimethylsulfoxide (DMSO), or acetone can be used to solubilize herbicides in the aqueous medium. DMSO and ethanol are not detrimental to the cells if the concentration is kept at 1% v/v or less.

Two formulations of triallate [S-(2, 3, 3-trichloroallyl)diisopropylthiocarbamate] were evaluated for their effectiveness in controlling wild oat (Avena fatua L.) in spring wheat (Triticum aestivum L.) in 12 field experiments conducted between 1967 and 1978. Control of wild oat was greater with fall applications of triallate granules than liquid or with spring applications of either liquid or granules. Further-more, 1.1 kg/ha of triallate granules applied in the fall controlled wild oat as well as did 1.7 kg/ha of liquid triallate applied in the fall. Wild oat control with triallate was usually better when soil incorporated than when surface applied regardless of formulation or time of application. Triallate granules controlled wild oat similarly on either plowed ground or wheat stubble; whereas, liquid triallate controlled wild oat better on plowed ground than wheat stubble. A delay of 8 h in triallate incorporation did not reduce wild oat control with either formulation; however, a delay of 24 h reduced wild oat control with the liquid formulation.

The allelopathic potential of germinating seed of velvetleaf (Abutilon theophrasti Medic.) was established in a laboratory study with germinating seed of turnip (Brassica rapa L. ‘Purple Top’). Two-day-old velvetleaf seedlings inhibited radicle growth of germinating turnip by 17% at 24 h after both were placed in the same petri plate. Alcoholic and aqueous extracts of velvetleaf seed, however, seriously inhibited germination of turnip seed. The extract of velvetleaf seed was fractionated by ion-exchange chromatography into acid, basic, and neutral fractions. Most of the allelopathic activity was located in the acid fraction, which includes the plant phenolics. The basic fraction (amino acids) inhibited radicle growth of turnip by 18% after 48 h. The amino acid profile of velvetleaf seed extracts is presented and discussed, because this fraction has previously been implicated as the allelopathic fraction.