The conversion of 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) to N-chloro-4-phenyl-3(2H)-pyridazinone glucosamine (hereinafter referred to as N-glucosyl pyrazon) in intact seedlings and in leaf discs of red beets (Beta vulgaris L., var. Detroit Dark Red) was significantly greater in the light than in the dark. Pyrazon conjugation with glucose was dependent on the carbohydrate status of the leaf tissue, since the formation of the N-glucoside in the dark was further reduced with dark pretreatment but could be restored to the level observed in the light by infiltrating the leaf discs with supplemental sucrose.

Compared to corn (Zea mays L.) (resistant), oats (Avena sativa L.) (susceptible), and giant foxtail (Setaria faberii Herrm.) (susceptible), fall panicum (Panicum dichotomiflorum Michx.) and large crabgrass (Digitaria sanguinalis (L.) Scop.) metabolized 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) at an intermediate rate. The order of tolerance of these five species (corn > fall panicum and large crabgrass > giant foxtail > oats) is identical to the order of their ability to metabolize atrazine. In 6 hr, corn, fall panicum, large crabgrass, giant foxtail, and oats metabolized 96, 44, 50, 17, and 2%, respectively, of the 14C-atrazine absorbed from a 10 ppm solution and translocated to the foliage, leaving concentrations of 2.2, 34.8, 30.1, 59.8, and 66.3 mμ moles, respectively, of atrazine per g of fresh weight of shoots. Hydroxyatrazine [2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine] was found in the shoots of corn and giant foxtail. Corn shoots also contained a more hydrophilic metabolite, presumably a peptide conjugate. Hydrophilic metabolites found in the shoots of giant foxtail, fall panicum, and large crabgrass were chromatographically identical to the hydrophilic metabolite found in corn.

Paper chromatographic separation of hydroxydimethylarsine oxide (cacodylic acid), monosodium methanearsonate (MSMA), sodium arsenate, and sodium arsenite was achieved with the aid of four solvent systems. Aqueous extracts of plant tissues removed essentially all the arsenicals applied, but methanolic fractionation was required before the extracts could be analyzed by paper chromatographic procedures. A standard nitric-sulfuric acid digestion procedure was employed for arsenic analyses, but great care was taken to avoid sulfuric-acid-induced charring by first adding relatively large amounts of nitric acid to drive off chlorides present. Depending upon the amount of chloride present, substantial losses of arsenic as arsine chlorides were observed if the samples charred. Five minutes in fuming sulfuric acid to completely break the carbon-arsenic bonds was another critical requirement for the quantitative determination of arsenic from cacodylic acid and MSMA. The silver diethyldithiocarbamate colorimetric method was useful for detecting as little as 0.6 μg or as much as 20 μg of arsenic per sample.

The adsorption of picloram (4-amino-3,5,6-trichloropicolinic acid) was studied for several Canadian prairie soils and for various other adsorbents. The kd values for the soils ranged from 0.09 to 0.75 and were correlated only with soil organic matter. The kd values for other adsorbents varied from 0 to 232, the order of adsorption being activated charcoal > anion exchange resin > peat moss > cellulose triacetate. There was no adsorption of picloram on montmorillonite and kaolinite clays, cation exchange resin, wheat straw (Triticum aestivum L.), or cellulose powder. The differences in the adsorption of picloram were explained on the basis of the relative affinities of the various adsorptive surfaces for the molecular or the ionized forms of the acid.

The differential response of three selections of johnsongrass (Sorghum halepense (L.) Pers.) to different temperatures and dark periods was studied in two experiments conducted in growth chambers. The three selections of johnsongrass were obtained from locations representing different climates. At 20 C all three selections grew equally with respect to most parameters of growth studied; however, at 35 C the selection from the southern climate produced more total fresh weight than the other two selections. Rhizome production and the number of stems also were greater in the southern selection at 35 C. An 8-hr dark period prevented flowering in all three selections and significantly reduced rhizome production in two selections compared to the 12-hr dark period. Flowering occurred most rapidly in the selection from a northern climate and most slowly in the selection from a southern climate. The results are discussed in relation to the possible plant adaptive changes and the possibility of weed control through dark period interruption.

Two new varieties of foxtails, Setaria viridis var. robusta alba Schreiber and Setaria viridis var. robusta-purpurea Schreiber are described. As their names imply, they differ from each other only in the color of their bristles but differ from Setaria viridis (L.) Beauv. and Setaria viridis var. major (Gaud.) Posp. in their robust growth habit, morphology, and physiological responses. A key distinguishes these from other species of similar habit and habitat.

Differential selectivity was shown for 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 2-chloro-4, 6-bis(isopropylamino)-s-triazine (propazine), and S-ethyl diisobutylthiocarbamate (butylate) on giant foxtail (Setaria faberi Herrm.) yellow foxtail (Setaria glauca (L.) Beauv.), giant green foxtail (Setaria viridis var. major (Gaud.) Posp.), robust white foxtail (Setaria viridis var. robusta-alba Schreiber), and robust purple foxtail (Setaria viridis var. robusta-purpurea Schreiber). The differentials obtained could explain the reports of uncontrolled Setaria species and the apparent increase of the latter three varieties. The two new varieties of green foxtail, robust white and robust purple foxtails, were the most tolerant varieties or species to atrazine and propazine with giant green foxtail intermediate between the robust foxtails and green, giant, and yellow foxtail. The ED50 values for the robust foxtails were also higher than for the other varieties and species studied. Yellow foxtail was the most tolerant to butylate. The effective rate, measured as percent of control, was directly related to soil organic matter content.

The absorption and translocation of foliarly applied 14C-labeled (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T-1-14C) in winged elms (Ulmus alata Michx.) as affected by season of application, air temperature, and soil moisture were determined by autoradiography of bark samples and liquid scintillation counting of leaf tissue. Treatments at 3-week intervals throughout the growing season showed highly variable trends in absorption and translocation within and between growing seasons. Seasonal variations in the absorption of 14C-2,4,5-T were similar to the variations in translocation. Translocation into the stem closely correlated with absorption into the leaves. Higher daily temperatures of 24 to 40 C appeared to enhance absorption and translocation. Variations in soil moisture showed little effect on absorption; whereas, a decrease in soil moisture reduced translocation from leaves to roots.