Translocation, distribution, and metabolism of 14C-carboxy-labeled dicamba (3,6-dichloro-o-anisic acid) in western bracken [Pteridium aquilinum (L.) Kuhn var. pubescens Underw.] were determined in field and greenhouse trials by liquid scintillation radioassays, autoradiographs, and paper chromatography. Absorption and translocation of 14C readily occurred from 14C-labeled dicamba applied to frond buds, pinnae of new leaves, and rhizome tissue. The translocated 14C tended to accumulate in opened fronds or if fronds had not emerged, in frond buds and rhizome apices. Dicamba applied to living tissue of a quasi-dormant rhizome in the field in spring was translocated to rhizome apices and metabolized to 5-hydroxy-3,6-dichloro-o-anisic acid and 3,6-dichlorogentisic acid 10 days after application.

A synergistic interaction occurred when sugarbeets (Beta vulgaris L. ‘Mono-Hy Al’) were treated with mixtures of ethofumesate (2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulphonate) and desmedipham [ethyl m-hydroxycarbanilate carbanilate (ester)]. Depending on the stage of weed growth synergistic interactions were also observed on two weed species: wild mustard [Brassica kaber (DC.) L.C. Wheeler ‘pinnatifida’ (Stokes) L.C. Wheeler] and wild oat (Avena fatua L.). Desmedipham penetrated the foliage more slowly than did ethofumesate. The rate of desmedipham penetration was positively correlated with the concentration of its formulants (solvents and adjuvants) in the spraying emulsion, and to a lesser extent with the formulants of ethofumesate. Increasing the spray volume also increased desmedipham penetration. None of these factors affected penetration by ethofumesate. 14C-labeled ethofumesate and desmedipham did not translocate out of treated leaves regardless of the concentration of formulants or active ingredients. These data suggest that the synergistic interaction is mainly due to the increased penetration by desmedipham when applied with ethofumesate.

Freshly-produced, mature prickly sida (Sida spinosa L.) seeds (18 to 21 days after anthesis, < 20% water content) were dormant and neither imbibed water nor germinated when incubated for up to 4 weeks under several light and temperature conditions. Over 80% of the freshly-produced, immature seeds (12 to 16 days after anthesis, > 20% water content) germinated when removed from the mother-plant before dehydration and incubated in alternating 20 to 30 C for 4 weeks. The onset of dormancy coincided with the later stages of seed dehydration and coat-hardening. Over 90% of the mature seeds imbibed water and germinated when incubated at 35 C after 4 months dry storage at 25 C. A puncture through the seed coat, either over the radicle or cotyledons, permitted water imbibition by all mature seeds, but the puncture over the radicle was significantly more effective in inducing germination. Seed coat impermeability was important, but was not the only factor responsible for prickly sida dormancy.

Ultraviolet (UV) absorption spectra were recorded of chloramben (3-amino-2,5-dichlorobenzoic acid) and selected relatives in solutions of different pH's. From these spectra, the Broensted acid-base properties of chloramben were deduced. Interpretations of solution spectra were applied to UV absorption spectra of chloramben adsorbed onto Ca-montmorillonite at low water content. Infrared (IR) transmittance spectra were recorded of chloramben and selected derivatives in KBr pellets and band assignments were made. Interpretations of these spectra were also applied to IR spectra of chloramben adsorbed onto Ca-montmorillonite at low water content. Both UV and IR measurements indicated that protonation of the amino group occurs and that the carboxyl group of chloramben is strongly hydrogen-bonded to the hydration water of the interlayer cations.

The persistence of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl] amino]-2-methylpropionitrile} both applied at 2.24 and 4.48 kg/ha was studied in the field on two soils. A greenhouse bioassay using cucumber (Cucumis sativus L. ‘Wisconsin SMR-18′) showed no reduction in growth when plants were grown in soil taken from cyanazine and atrazine treatments at the end of the season. Similarly, fall-sown rye (Secale cereale L.) was not injured. The yields of transplanted tomatoes (Lycopersicum esculentum L. ‘Campbell 28′) and transplanted watermelons (Citrullus vulgaris ‘Crimson Sweet’) were not significantly reduced when grown 1 yr after the initial application of either herbicide.

Effects of temperature on response of transplanted tomatoes (Lycopersicon esculentum Mill. ‘Campbell 17′) to trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine], and isopropalin (2,6-dinitro-N,N-dipropylcumidine) were investigated in field studies. Trifluralin and nitralin caused greater reductions in growth and yields of tomatoes transplanted early in April than to tomatoes transplanted around May 1. Responses to profluralin were similar but total yields of early transplanted tomatoes were not reduced although initial yields were below those of tomatoes treated with isopropalin. In controlled environment chamber studies, percent phosphorus of plant tops was reduced by trifluralin at low temperatures but was not influenced by trifluralin at high temperatures. Tomoto responses to phosphorus as reflected by plant fresh weight, dry weight and phosphorus content (mg/plant) were reduced by trifluralin at low and high temperatures.

The phenetic relationships of green foxtail [Setaria viridis var. viridis (L.) Beauv.] and its allies were examined by numerical and chemotaxonomic methods. Correlation coefficients and taxonomic distances based on quantitative data from 31 characters displayed close phenetic similarities among green foxtail, its varieties and foxtail millet [S. italica (L.) Beauv.]. Isolation and separation of 35 alcohol-soluble compounds by two dimensional paper chromatography supported the numerical comparisons. By combining all characters examined, the resulting cluster analysis displayed the closest similarity between robust white (S. viridis var. robusta-alba Schreiber), robust purple (S. viridis var. robusta-purpurea Schreiber) and giant green foxtail [S. viridis var. major (Gaudin.) Posp.] indicating that the robust foxtails may be subvarieties of giant green foxtail rather than of green foxtail. The numerical, morphological and chemical comparisons support the proposed phylogeny of the Old World foxtails and indicate green foxtail as the probable center of ancestorial origin.

Aseptic cultures of isolated corn (Zea mays L. ‘North Dakota KE47101′) shoots and roots and soybean [Glycine max (L.) Merr. ‘Hawkeye’] seedlings absorbed and metabolized atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] similarly to plants grown and treated in nutrient solution under non-sterile conditions. Atrazine injured susceptible soybean seedlings more rapidly than can be explained on the basis of starvation alone. It is postulated that the herbicidal activity of atrazine is partly due to toxic secondary factor(s) which may be of biochemical or photochemical origin. The effect of the toxic secondary factor(s) was reversed by added sucrose independent of light.

Preemergence applications of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], chloramben (3-amino-2,5-dichlorobenzoic acid), fluometuron [1,1-dimethyl-3-(α,α,α-trifluro-m-tolyl)urea], propachlor (3-chloro-N-isopropylacetanilide), and trifluralin (α,α,α-trifluro-2,6-dinitro-N,N-dipropyl-p-toluidine) were compared in 10 North Carolina soils and the relationship of activity to soil physical and chemical properties appraised. Oats (Avena sativa L. ‘Carolee’) were used as the indicator plant in bioassays under greenhouse conditions. Fifteen soil properties were measured and correlated with herbicide I50 (50% fresh weight inhibition) values. Organic matter was the soil variable most highly correlated with herbicide phytotoxicity. There was an inverse relationship between herbicide water solubility and inactivation by organic matter. Volume weight determinations and water holding capacity values (0.1 bar) provided relatively good estimates of soil organic matter contents, but were not as highly related to herbicide activity as organic matter content.

Leaf surfaces of fifteen plant species contained a large variety of biological and nonbiological structures of various sizes and shapes, which are not a part of the leaf surface but are significant features of all field-grown plants. Some of these structures were fungal hyphae, soil, pollen grains, bacteria, smut teliospores, and many others which could not be identified. This profusion of extraneous material indicates that in-depth studies will have to be made concerning the influence of these materials on agricultural chemicals before the fate of the chemical can be determined with any certainty.

The response of net photosynthetic rate to temperature and light, the rate of photorespiration, the compensation concentration for CO2, and the pathway of CO2 fixation in smooth pigweed (Amaranthus hybridus L.) were investigated using infrared gas analysis and 14CO2. Maximum net photosynthetic rates of whole shoots were 45 mg CO2 dm-2 hr-1 at 30 C and 7.8 klux. Intact whole shoots were not light saturated at 10 klux. The optimum temperature for net photosynthesis was between 30 C and 40 C. Photorespiration was low and the CO2 compensation concentration was 7 ppm. After a 5-sec exposure to 14CO2 in the light, label was detected in oxaloacetate, malate, and aspartate. It was concluded that smooth pigweed has the gross photosynthetic characteristics and CO2 fixation pathway typical of C4 or Hatch-Slack plants.