Two wild oat (Avena fatua L.) biotypes and two barley (Hordeum vulgare L.) varieties known to have intraspecific differential response to foliarly-applied 4-chloro-2-butynyl m-chlorocarbanilate (barban) were studied. When barban was applied to the roots, the intraspecific differential response (measured by shoot retardation) was maintained in both species but to a much lesser extent than previously observed with foliar application. Wild oat maintained a greater differential response than barley. Therefore, the factors causing the differential response to foliarly-applied barban may reside primarily in the leaves of both species but to some extent elsewhere (perhaps at the plant apex) in the wild oat biotypes and to a lesser extent elsewhere in the barley varieties. Differential response to foliar applications was not caused by differential uptake, but may be caused primarily by the susceptible biotype or variety's reduced ability to degrade barban beyond 3-chloroaniline. This might cause the greater build-up of compound X (a water-soluble 3-chloroaniline-containing metabolite of barban) observed in the susceptible biotype or variety. Compound X appeared to be nonphytotoxic. The build-up of compound X in turn may reduce the rate of metabolism of barban resulting in the greater amount of free barban found in the treated leaf of the susceptible biotype or variety 12 to 24 hr after treatment. This greater amount of free barban in the leaf of the susceptible biotype or variety may be responsible for the differential response to foliar applications of barban. Evidence for this partial explanation of the differential response was better for barley than for wild oat.

Primary leaves of 17-day-old-bean (Phaseolus vulgaris L. ‘Black Valentine’) were treated with 14C-labeled dimethylsulfoxide (DMSO), 3,6-dichloro-o-anisic acid (dicamba), 1,1′-dimethyl-4,4′-dipyridinium salt (paraquat), and 2-chloro-4-(ethylamino)-6-(isopropylamino-s-triazine (atrazine). Each herbicide was tested alone, and in combination with 30% DMSO, 0.25% Tween 80 (nonionic surfactant containing polyoxyethylene sorbitan monooleate), or both. DMSO at concentrations of 25% or more caused varying degrees of acute toxicity. However, a small amount of radioactive carbon generally was distributed throughout the plant 5 days after application of DMSO-14C, as determined by autoradiography and counting. Tween 80 enhanced whereas DMSO had little effect on the absorption and translocation of dicamba, a phloem-mobile herbicide. The contact toxicity and apoplastic movement of paraquat was increased with DMSO. Tween 80 enhanced eight-fold and DMSO, two-fold, the foliar uptake and (apoplastic) movement of atrazine within the treated leaves.

Corn (Zea mays L. ‘Dixie 18′) leaf discs were incubated in light or darkness in dilute solutions of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) with and without 6-furfurylamino-purine (kinetin). Kinetin decreased chlorophyll loss in light whereas atrazine had no effect. In darkness atrazine at a concentration of 5 × 10−8M increased clorophyll a retention in the absence of exogenous kinetin; but in the presence of 1.5 μg/ml of kinetin, the herbicide increased loss of chlorophyll a. Increasing the kinetin concentration to 15 μg/ml relieved the effect of 5 × 10−8M atrazine, but 10−7M atrazine increased chlorophyll loss. Higher concentrations of kinetin (150 and 1500 μg/ml) prevented all effects of atrazine. Factorial analysis revealed a highly significant interaction between atrazine and kinetin.

The absorption by bean (Phaseolus vulgaris L. ‘Black Valentine’) of 2,4-bis-(isopropylamino)-6-(methylthio)-s-triazine (prometryne) at 1 μM concentration was increased in the presence of 10, 1, or 0.1 μM O,O-diethyl S-(ethylthio) methyl phosphorodithioate (phorate). An increase in absorption of 10 μM prometryne with addition of 1 μM phorate was recorded after 72 hr, but no increase was seen after 96 hr of absorption. Both prometryne and phorate inhibited state 3 respiration of mitochondria isolated from 6-day-old bean hypocotyls. Inhibition increased with increasing pesticide concentrations. When the pesticides were applied simultaneously, no interactions affecting state 3 respiration were observed. Neither prometryne nor phorate alone significantly affected phosphate accumulation by bean shoot mitochondria.

Upon germination, one or more rhizomes grew from the apical end of each yellow nutsedge (Cyperus esculentus L.) tuber. Each rhizome developed a basal bulb upon exposure to light. No significant differences in germination percentages existed between four lots of tubers which differed about fivefold in weight. The weight of plant material produced correlated significantly with the fresh weight of the tuber from which it emanated. When tubers germinated three successive times, over 60% of the tuber dry weight, carbohydrate, oil, starch, and protein were consumed during the first germination; but less than 10% of these constituents were uitlized during each of the next two germinations. Plants weighed significantly more after 43 and 91 days of growth with tubers attached throughout the period than when tubers were detached after emergence.

Achenes of Scotch thistle (Onopordum acanthium L.) contain a water-soluble germination inhibitor and are sensitive to differences in light quality. Germination of these achenes can be enhanced by the addition of 0.14 mmole of gibberellic acid and 1.0 mmole of potassium nitrate to the substrate. Dissected embryos exhibit germination responses similar to those observed for achenes. Naturally-distributed achenes recovered from the soil in the field increased in germination under fluorescent light and after washing. Achenes will not germinate on the surface of a constant-moisture-supplying substrate when exposed to an unsaturated atmosphere. The physical environment of the seedbed apparently is paramount in controlling germination and persistence of achenes of Scotch thistle.

The uptake of 14C-labeled butoxyethanol ester of (2,4-dichlorophenoxy)acetic acid (BEE of 2,4-D) from water by three species of fed and fasted fish was studied. Fish were exposed to either 0.3 or 1.0 mg/L of herbicide for up to 168 hr. Combined residues of the 2,4-D ester and its metabolic products were determined radiometrically in eight tissues and organs. Extracts of these organs were examined by thin layer chromatography and autoradiography. Maximum residue concentrations were observed in most organs of fed fish within 1 to 2 hr of exposure, and within 1 to 8 hr of exposure for fasted fish. After maximum residue concentrations were reached, the herbicide and/or its metabolites were eliminated rapidly.

The use of herbivorous fish for the biological control of aquatic weeds has great potential. The susceptibility of most herbivorous fish to low temperature is the principal factor limiting their use in the United States. The white amur (Ctenopharyngodon idella Val.) can tolerate low temperature and other water quality extremes. This fish has a voracious appetite for many aquatic plants, and after attaining a length of 30 mm, it is almost exclusively phytophagous. Factors affecting the feeding habits of the white amur include the species of plants and water temperature. The white amur has been introduced for aquatic weed control in various countries. This fish might ameliorate some of the aquatic weed problems in the United States, and also provide a new source of protein.

Persistence and movement of 4-amino-3,5,6-trichloropicolinic acid (picloram) were studied in silty clay loam soils located at Hays and Newton, Kansas. At Hays, picloram was applied to a Harney silty clay loam at rates of 2.24 and 3.36 kg/ha in 1963, 1964, 1965, 1966, and 1968 and at Newton to a Goessel (tentative) silty clay loam at rates of 1.12, 2.24, and 3.36 kg/ha in 1966. Fifteen, 20, or 30-cm increments of soil were taken from as deep at 2.4 m below the soil surface and bio-assayed with soybeans (Glycine max (L.) Merr. ‘Clark 63′) in 1968 and 1969. In both soils the highest concentration of phytotoxic residue remained near the soil surface, but differences between the two sites were evident. In the Goessel soil phytotoxic residues were detected only near the surface. In the Harney soil movement was uneven, but residues were detected as deep as 2.4 m below the surface. Soil cracks probably contributed to penetration of small amounts of the herbicide to as much as 2.4 m below the surface. Total picloram remaining in both soils diminished with time.

Absorption and translocation of the 14C-labeled herbicide 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione (bioxone) in cotton (Gossypium hirsutum L. ‘Acala 4-42-77′) were studied using autoradiography and counting. Foliar penetration and acropetal distribution of 14C occurred within 3 hr and increased with time. No basipetal translocation of 14C out of treated leaves was detected 6 days after treatment. Radioactivity first occurred in the leaf veins, then more generally in interveinal tissues distally from the point of application. Absorption into roots of 30-day-old plants via nutrient solution was rapid; translocation into stem and leaves occurred 12 to 24 hr after treatment. Translocation of 14C was more rapid in 40-day plants. Radioactivity in leaves of root-treated plants was first located in the veins, then distributed throughout with accumulation of 14C in lysigenous glands and leaf margins. Little 14C moved into young growing points; most accumulated in older leaves. Plants treated with heterocyclic ring-labeled and phenyl ring-labeled bioxone-14C had similar distribution patterns of 14C, characteristic of compounds which move only in the apoplast.

The absorption and translocation of 14C in 14C-ring-labelled 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) at 1 and 7 days after foliar treatment of soybean [Glycine max (L.) Merr.] and cocklebur (Xanthium sp.) were investigated at 3, 5, 7, and 11 weeks after planting by means of radioautography and standard radioassay methods. Partitioning of radioactivity varied with plant age and with treatment time. Although a species difference was not observed in the total uptake of 2,4-DB, the rate of penetration of the herbicide was greater in cocklebur than in soybean. The 2,4-DB was retained in the treated leaf and was not translocated to other plant parts. Translocated radioactivity occurred principally in actively growing parts of both species, but only trace quantities were detected in soybean. No radioactivity was detected in the lower leaves of either plant. Plant response to 2,4-DB may be partially explained on the basis of differential penetration and translocation.

Single applications of 4.48 and 22.4 kg/ha of the ester formulation of (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T ester), 2,4,5-T amine, and 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) to the ground cover and soil under apple (Malus sylvestris Mill.) trees significantly reduced the proportion of broadleaf plants to grasses. After six annual applications of these herbicides, the ground cover consisted of almost pure stands of grasses. Six applications of 2-sec-butyl-4,6-dinitrophenol (dinoseb) + oil at 4.2 kg/ha + 374 L/ha and five times this rate decreased the proportion of broadleaf weeds to grasses, but one application did not change the proportion. One and six annual applications of dinoseb amine at 16.8 and 84 kg/ha significantly reduced the percentage of broadleaf weeds. One application of 3-amino-s-triazole (amitrole) at 4.48 kg/ha and six annual applications of amitrole at 22.4 kg/ha significantly decreased the percentage of broadleaf weeds. Six annual applications of 2,2-dichloropropionic acid (dalapon) + dinoseb amine at 47.6 + 84 kg/ha significantly increased the percentage of broadleaf weeds, especially mouseear chickweed (Cerastium vulgatum L.) and red sorrel (Rumex acetosella L.). Six annual applications of ammonium sulfamate (AMS) at 168 and 840 kg/ha increased the proportion of grasses to broadleaf weeds as did a single application at 168 kg/ha. AMS caused phytotoxic symptoms on young apple replants at the 168-kg/ha rate and also on mature trees at the 840-kg/ha rate. No phytotoxic symptoms were noted with the other herbicides applied.