A study was made on the absorption and translocation and of the effects of perfluidone [1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl) phenyl] methanesulfonamide] on the morphology and anatomy of cotton (Gossypium hirsutum L.) and yellow nutsedge (Cyperus esculentus L.). Concentrations of 1 μM to 10 μM perfluidone added to the nutrient solutions retarded growth of both species. Necrotic spots appeared on the lamina of cotton leaves which were expanded previous to the treatment. Cotton plants resumed normal growth within 11 days after removal of the herbicide. Yellow nutsedge plants remained stunted 18 days after removal of the herbicide. After 6 days, cotton and yellow nutsedge had absorbed 5.4% and 1.7%, respectively, of the 14C-perfluidone (uniformly labeled in the toluidine ring) added to the nutrient solution. Of the 14C absorbed by the plant, cotton and nutsedge translocated 20% and 30%, respectively, to the shoots. A 10-fold higher concentration of 14C was found at the leaf tips of nutsedge than in the other shoot tissues. In cotton shoots the 14C was distributed evenly. Perfluidone inhibited the mitotic indexes of cotton and nutsedge roots 78% and 100%, respectively, in 5 days.

Smutgrass [Sporobolus poiretii (R. & S.) Hitchc.] was selectively controlled in carpetgrass (Axonopus affinis Chase) and common bermudagrass [Cynodon dactylon (L.) Pers.] with atrazine [2-chloro-4-(ethylamino) −6-(isopropylamino)-s-triazine] applied at 2.2 kg/ha in each of two applications. MSMA (monosodium methanearsonate) applied alone or in combination with 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 2.2 + 0.6 kg/ha in each of three applications controlled at least 70% of smutgrass in two of three experiments. The common bermudagrass showed signs of atrazine injury during the first 6 weeks after treatment but the injury was not evident the following year. MSMA alone or in combination with 2,4-D killed carpetgrass in all experiments. Repeated treatments with bromacil (5-bromo-3-sec-butyl-6-methyluracil) applied alone or in combination with diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] controlled smutgrass but severely injured the turfgrasses.

EPTC (S-ethyl dipropylthiocarbamate), 1,8-naphthalic anhydride (NA), N,N-dialryl-2,2-dichloroacetamide (R-25788), CDAA (N,N-diallyl-2-chloroacetamide) and CDEC (2-chloroallyl diethyldithiocarbamate) at concentrations of 10-5 M inhibited the incorporation of acetate-1-14C (Ac∗) into fatty acids of isolated spinach (Spinacia oleracea L.) chloroplasts. Lower concentrations of these chemicals did not affect acetate incorporation into fatty acids. However, the inhibition by EPTC at 10-5 M was counteracted by NA and R-25788 [agriculturally important antidotes for EPTC injury to corn (Zea mays L.)] at 10-7 M.

Purple nutsedge (Cyperus rotundus L.) from single tubers was grown for 3 months at 24, 32, and 40 C and 9, 13, and 19 klux illumination. Growth in number and dry weight of shoots, bulbs, and tubers were determined at monthly intervals. Maximum growth for all portions of the plant occurred after 3 months at 32 C and 19 klux illumination. Minimum growth occurred at 40 C and 9 klux illumination. Growth at 24 C was not significantly affected by increased illumination above 9 klux.

Atrazine [2-chloro-4-(ethylamino)-6-(isopropyl-amino)-s-triazine] applied to the soil of potted tomatoes (Lycopersicon esculentum Mill. ‘John Baer’) reached its maximum concentration in the xylem exudate collected from the stumps of detopped plants in 6 to 8 hr but continued to accumulate in the petioles for 36 hr. An atrazine concentration of 3.8 μg/g fresh weight of petiole at 12 hr after treatment was approximately the same as the maximum concentration of atrazine in the xylem exudate indicating that atrazine had accumulated extensively in tissues outside of the xylem vessels.

EPTC (S-ethyl dipropylthiocarbamate) (33 μM) and diallate [S-(2,3-dichloroallyl)diisopropylthiocarbamate] (90 μM) inhibited the incorporation of 6 mM acetate-2-14 C (Ac∗) by 80% and 65%, respectively, and the incorporation of 0.5 μM malonate-2-14C (Mal∗) by 32% and 26%, respectively, into the lipids of spinach (Spinacia oleracea L.) chloroplasts. The inhibition of Ac∗ or Mal∗ incorporation into lipids was not observed in the presence of excess Ac∗ or Mal∗, respectively. Incorporation of palmitate-1-14C and oleate-1-14C into chloroplast lipids was inhibited by EPTC and diallate. Mal∗ incorporation into dienoic fatty acids was inhibited by EPTC and diallate. The concentration of EPTC and diallate inhibiting lipid synthesis falls into the physiological range of these herbicides, explains some metabolic effects of these compounds, and fits as the mode of activity of these herbicides.

Simulated rainfall less than 8 hr after postemergence application of bentazon (3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2, 2-dioxide) reduced its activity on velvetleaf (Abutilon theophrasti Medic.) and common cocklebur (Xanthium pensylvanicum Wallr.) in greenhouse studies. In field studies, simulated rainfall less than 24 hr after application reduced bentazon's activity on velvetleaf. on common cocklebur, bentazon's activity was reduced even if simulated rainfall was delayed for more than 24 hr after application. In greenhouse studies, spray adjuvants (vegetable or petroleum oil) were helpful in overcoming the detrimental effects of simulated rainfall. Greenhouse and field studies indicated that soybeans [Glycine max (L.) Merr.] could tolerate bentazon-oil adjuvant combinations.

In field studies, herbicides were applied at various times to different plots during the summer and fall at two locations over a 3-year period to control winter weeds in nonoverseeded bermudagrass [Cynodon dactylon (L.) Pers.] turf. Annual bluegrass (Poa annua L.) control was higher at Griffin for all herbicide applications made in October when compared with herbicide applications made at the same rate in July, August, or September. At Lawrenceville, optimum annual bluegrass control was obtained when bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl) benzenesulfonamide] was applied in August, terbutol (2,6-di-tert-butyl-p-tolyl methylcarbamate) applied in either August or September, benefin (N-butyl-N-ethyl-α,α,α-trifluoro −2,6 dinitro-p-toluidine) applied in September, pronamide [3,5-dichloro-N-(1,1-dimethyl-2-propynyl) benzamide] applied in either September or October, and simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] applied in October. DCPA (dimethyl tetrachloroterephthalate) did not control annual bluegrass satisfactorily at either location, regardless of dates of application. The control of several broadleaf weeds was generally higher when herbicides were applied in October at Griffin and when applied in September or October at Lawrenceville when compared with earlier treatments. Bensulide applied in October was the only herbicide that satisfactorily controlled parsley-piert (Alchemilla microcarpa Boissie Reuter).

Field studies were conducted to evaluate the effectiveness of one, two, and three annual applications of atrazine [2-chloro-4-(ethylamino) −6-(isopropylamino)-s-triazine], 2,4-D [(2,4-dichlorophenoxy) acetic acid], dicamba (3,6-dichloro-o-anisic acid), and a three way mix of dicamba, mecoprop [2-[(4-chloro-o-tolyl) oxy]propionic acid], and 2,4-D at a ratio of 7:5:20 at different stages of development for the control of Canada thistle [Cirsium arvense (L.) Scop.]. Two consecutive annual applications in all atrazine treatments achieved the same level of control as cultivation every 5 weeks. In the year of the last treatment, Canada thistle was controlled with two or more consecutive annual applications of the hormone-type herbicides (2,4-D, dicamba, and the three way mix); however, in the year following the last treatment, regrowth occurred.

The volatilities of iso and normal butyl esters of 2,4-D [(2,4-dichlorophenoxy)acetic acid] in a commercial formulation applied as thin films on pyrex and as aqueous droplets on pyrex and leaf surfaces increased directly with the available surface area/applied dose ratio (Q), and inversely with the adsorptive and absorptive characteristics of the surface, under the same conditions of temperature (39 ± 1.5 C), relative humidity (RH) (0%), geometry, airflow rate (750 ± 7 ml/min) and light. Partial pressures and rates of volatilization were computed. Herbicide in droplets below 200μ in diameter tended to volatilize faster than it penetrated, but the reverse occurred above this diameter.

The uptake of 14C labeled bromacil [5-bromo-3-sec-butyl-6-methyluracil] by wheat plants (Triticum aestivum L. ‘Gaines’) grown in a Woodburn silt loam was studied at soil water potentials of −0.35 and −2.50 bars, and in solutions containing 2.0 and 4.5 μg/ml bromacil. Transpiration rate, shoot and root dry weight, and bromacil content were measured as a function of time. Bromacil uptake into the root and foliar portions of the wheat plants increased with time. At the low bromacil concentration, 70%, and at the high concentration, 42%, more bromacil was taken up by the plant at the higher soil water potential. Uptake of bromacil increased concurrently with increased transpiration of water. The bromacil concentration in the transpiration stream was greater at the −0.35 bar than at the −2.50 bar soil water potential at both bromacil application rates. Transpiration rates of the plants treated with bromacil were nearly the same after a 40-hr exposure at both soil water potentials. The rate of bromacil uptake and accumulation may be influenced by the effect of soil water potential on the apoplastic movement of water and solutes in the roots.

Various growth regulators, carrier systems, and ammonium thiocyanate (NH4SCN) additions in combination with herbicide mixtures were evaluated for their foliar phytotoxicity to winged elm (Ulmus alata Michx.). Silvex [2-(2,4,5-trichlorophenoxy)propionic acid] and 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] were more effective than the dichlorophenoxy herbicides. Additions of NH4SCN to the ester of 2,4,5-T consistently increased control. Picloram (4-amino-3,5,6-trichloropicolinic acid) was the most effective herbicide for killing the trees, and in mixtures with the phenoxy herbicides consistently produced good tree kill. No increase in 2,4,5-T activity could be attributed to additions of growth regulators, concentrated nutrient solutions, or to type of carrier system used.

The effectiveness of postemergence applications of triallate [S-(2,3,3-trichloroallyl)diisopropylthiocarbamate] for wild oat (Avena fatua L.) control in spring wheat (Triticum aestivum L. ‘Waldron’) was evaluated in the field and greenhouse. The stage of the wild oat plants at the time of treatment did not appear to influence wild oat control with postemergence applications of triallate in the field; however, in the greenhouse, wild oat plants became more resistant with increased maturation. Granular triallate was more effective than the emulsifiable concentrate for postemergence wild oat control. Fair season-long postemergence wild oat control was obtained with the granular formulation of triallate at rates of 2.24 kg/ha or greater. However, some wheat injury was observed in the field with the 2.80 and 3.36 kg/ha rates of granular triallate. Moisture and temperature influenced postemergence wild oat control with triallate.

Studies were conducted to examine over time the effects of propachlor (2-chloro-N-isopropylacetanilide) on the growth of cucumber (Cucumus sativus L. ‘Straight Eight’) roots and associated biosynthetic reactions. Complete inhibition of root elongation occurred within 16 hr after exposure to propachlor. Inhibition of growth was not found to be a result of an effect on ATP formation or respiration. Protein biosynthesis was reduced several hours before the observed inhibition of growth therefore implicating it as the causal factor. Inhibition of protein synthesis occurred prior to an observed reduction in RNA synthesis suggesting that the primary effect of propachlor is on protein biosynthesis and that its effect on nucleic acid synthesis is secondary. It is concluded that the primary mechanism of action of propachlor is its effect on nascent protein biosynthesis.

Pronamide [3,5-dichloro-N-(1,1-dimethyl-2-propynyl)benzamide] was most phytotoxic to oat (Avena sativa L.) when placed in the seed zone and to quackgrass (Agropyron repens (L.) Beauv.), when placed in the rhizome zone. Inhibition of part of the buds by pronamide on detached quackgrass rhizome sections did not influence other buds. Foliar applications of pronamide were not phytotoxic to established oat or quackgrass. Foliar-applied 14C-pronamide showed little uptake by quackgrass. Application to the roots of established plants showed rapid root uptake and movement to the foliage. 14C-pronamide was rapidly absorbed by oat seedlings for the first 0.5 hr and subsequently at a much slower rate. Over 60% of the pronamide taken up after 1 hr was exchangeable. Pronamide was adsorbed to the cell walls of treated roots, but little was associated with nuclear, mitochondrial, microsomal, or soluble protein fractions. Pronamide was adsorbed to varying degrees depending on soil type. Adsorption was more highly correlated with soil organic matter content than with cation exchange capacity, clay content, or pH.

Pronamide [3,5-dichloro-N-(1,1-dimethyl-2-propynyl)benzamide] inhibited root and shoot growth, but had little effect on the germination of oat (Avena sativa L.) or cucumber (Cucumis sativus L.), and sprouting of quackgrass [Agropyron repens (L.) Beauv.] buds. Root growth was more sensitive than shoot growth. Pronamide decreased the longitudinal growth rate and caused radial enlargement in the elongation region of the roots of oat seedlings within 4 hr. Dry weights of the swollen root tips increased 6% over the controls after 4 hr. Pronamide stopped the growth of established oat plants within 24 hr when added to nutrient culture medium. It caused a slight increase in 86Rb uptake by excised oat roots. Pronamide stopped normal mitosis in treated oat roots within 0.5 hr. Examination of treated root tips under a microscope showed numerous cells in arrested metaphase, c-pairs, multinucleate cells, polyploidy and swollen and misshapen nuclei. Incorporation of 14C-glucose into oat root cell walls and 14C-leucine into protein were increased by 26 and 20% respectively, following 4-hr incubations in pronamide. The primary mode of action of pronamide is mitotic poisoning.