Experiments were conducted with isolated protoplasts of wild oat (Avena fatua L. # AVEFA) and isolated chloroplasts of wild oat and wheat (Triticum aestivum L.), to determine if the methyl sulfate salt of difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) might influence photoreactions in these species. Difenzoquat did not affect CO2 fixation, uncoupled electron transport, or proton uptake. At concentrations of 0.5 mM and 1 mM, difenzoquat caused a slight, but statistically significant, inhibition of photophosphorylation. Experiments assaying coupled electron transport indicated that inhibition of photophosphorylation occurred not through uncoupling, but by an energy-transfer inhibition. This same effect was observed in isolated mitocondria of both species, with about 50% inhibition of state 3 respiration rates occurring with 10 μM difenzoquat. However, no important differentials were observed in the relative susceptibilities of wheat and wild oat mitochondria. Difenzoquat also functioned as a weak autooxidizing electron acceptor in photosynthetic electron transport. Therefore, difenzoquat-induced leaf chlorosis and necrosis may result from a bipyridilium-type electron acceptor activity if sufficient herbicide is absorbed.

Storage of intact Texas gourd [Cucurbita texana (A.) Gray] pepos for 21 days after harvest increased germination of seeds from pepos collected 15 to 47 days after flowering. Germination increased as day length decreased and as osmotic potential of germination media increased. Temperatures of 20, 25, and 30C resulted in 72, 93, and 99% germination, respectively. No seeds germinated at 10 or 40C. Seedling emergence decreased as planting depth increased, with no emergence from 12.5 cm. Control of Texas gourd in soybeans [Glycine max (L.) Merr.] was achieved with preemergence applications of metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one], metribuzin plus alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)-acetanilide], and oxadiazon [2-tert-butyl-4 (2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one], with successful control partially dependent on soil and climatological conditions. Postemergence treatments that resulted in adequate control included applications of acifluorfen {5-[2-chloro-4-(trifluoromethyl)-phenoxy]-2-nitrobenzoic acid}, oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene], and metribuzin plus 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] applied at an early soybean growth stage and repeated.

Glyphosate [N-(phosphonomethyl)glycine], dalapon (2,2-dichloropropionic acid), or paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) applied for edging control of bermudagrass [Cynodon dactylon (L.) Pers. ‘common ‘ # CYNDA] did not injure any of the eight woody ornamental species included in a 3-yr study. Paraquat applied in seven applications per year did not effectively control bermudagrass. Bermudagrass control was variable with glyphosate and dalapon during spring and summer; but repeated treatments at approximately 4-week intervals maintained effective control. In most instances, bermudagrass control was higher with glyphosate than with dalapon during September and October.

Napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide]-binding in excised root segments of corn (Zea mays L. ‘NC + 59′) was confined to cell wall fractions (residue and 500 g pellet) remaining after homogenization and to components of the 100 000 g supernatant. Binding increased in both the cell wall and soluble fractions with continued exposure to napropamide. Microautoradiographs revealed that the napropamide bound in the cell walls was located in epidermal, cortical, and stelar tissue. Various proteins were capable of binding napropamide in vitro; however, protease treatment did not liberate the radioactivity bound in the cell wall fragments. Carbohydrate release from the cell wall material with cellulase was not correlated with the solubilization of bound radioactivity and wall carbohydrate monomers did not appear to bind to napropamide in vitro. A portion of the radioactivity found in the soluble components (at 100 000 g) was associated with a molecule of MW > 600. The continued influx of napropamide was due to binding to cell wall components and molecules within the cell.

Research was conducted at Rosemount, Minnesota in 1979 and 1980 to evaluate the effect of soil moisture on quackgrass [Agropyron repens (L.) Beauv. # AGRRE] interference in soybeans [Glycine max (L.) Merr.]. Four treatments were studied: 1) nonirrigated soybeans, 2) irrigated soybeans, 3) nonirrigated soybeans, quackgrass-infested, and 4) irrigated soybeans, quackgrass-infested. Percent N, P, and K of soybeans was not affected by quackgrass interference. Irrigation did not increase the yield of quackgrass-free soybeans. The yield of quackgrass-infested soybeans was increased by irrigation when soil moisture was limited, but yields were always less than quackgrass-free soybeans. Quackgrass was nearly the same height or taller than the soybeans at all stages of soybean development and offered substantial competition for light throughout the growing season. This research indicates that an adequate supply of soil moisture can reduce quackgrass interference in soybeans, but cannot eliminate it, since quackgrass apparently continues to compete with soybeans for light.

Freshly harvested smallflower morningglory [Jacquemontia tamnifolia (L.) Griseb. # IAQTA] seed germinated best after 25 to 60 s of scarification in an electric scarifier equipped with 100 to 120 grit emery cloth. Optimum temperature for germination was 25C. At 10 and 45C no germination occurred for up to 7 days. Eight and 12 days after planting in silt loam soil there was 85 and 98% emergence of smallflower morningglory from depths of 0.5 to 1 cm, whereas no emergence was observed from depths of 6 cm or greater 12 days after seeding.

Field and greenhouse experiments in 1981 and 1982 determined the potential interactions of three preemergence and three postemergence herbicides with four granular insecticides in soybeans [Glycine max (L.) Merr.]. Generally, metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] increased soybean injury and lowered yields when applied to plots treated with an organophosphate insecticide at planting. Soybean injury from these treatments and from aldicarb [2-methyl-2-(methylthio)-propionaldehyde-o-(methylcarbamoyl)oxime] plus metribuzin applied in the field was greater in 1982 than 1981 due to excessive rainfall immediately after planting. Oryzalin (3,5-dinitro-N4,N4 -dipropylsulfanilamide) plus several of the in-furrow insecticide treatments in the greenhouse increased injury to soybeans. Other than this, the method of insecticide application, banded or in-furrow, had no effect on that caused by each pesticide combination.

Rosering gaillardia (Gaillardia pulchella Foug. # GAIPU) and other herbaceous broadleaf plants were effectively controlled for one season by sprays of 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 1.1 kg ae/ha or glyphosate [N-(phosphonomethyl)glycine] at 1.1 kg ai/ha, or a 4:1 combination of 2,4-D and picloram (4-amino-3,5,6-trichloropicolinic acid) at 0.7 kg ae/ha applied in late March in the southern Rolling Plains of Texas. Production of perennial warm-season grasses increased 428, 480, 728, and 1440 kg/ha on a clay site 7 months after spraying with 2,4-D, 2,4-D plus picloram (4:1), atrazine [2-chloro-4-(ethylamino)-6-isopropylamino-s-triazine], and glyphosate, respectively. Application of 4.4 kg ae/ha of dalapon (2,2-dichloropropionic acid) severely damaged perennial warm-season grasses. Annual cool-season grasses were effectively controlled with sprays of atrazine or glyphosate at 1.1 kg ai/ha or dalapon at 4.4 kg ae/ha. Texas wintergrass (Stipa leucotricha Trin. & Rupr.) production was greatest on rangeland treated with 2,4-D or 2,4-D plus picloram (4:1).

Field studies were conducted in 1979 and 1980 to determine yield losses caused by perennial sowthistle (Sonchus arvensis L. # SONAR) in rapeseed (Brassica napus L., B. campestris L.) fields in Saskatchewan and Manitoba. The relationship between percentage yield loss and density of perennial sowthistle was expressed by the linear regression equation y = −3.81 + 13.76 rdx. Weed survey data indicated that perennial sowthistle occurred in 39% of the rapeseed fields but infested only 7% of the hectares surveyed. Using both the survey data and the yield loss equation, the average annual loss in rapeseed yield was estimated to be 9.4 million kg in Saskatchewan and 6.1 million kg in Manitoba, with a value of 2.6 million and 1.7 million dollars (Cdn.), respectively. Perennial sowthistle occurs with a similar frequency and density in other crops so that the total loss from this weed would be much greater.

The adsorption of naphthalene by a Bosket loam soil was studied at 6.5, 15, 25, and 37C. Because the solubility and vapor pressure of naphthalene are precisely known over this temperature range, a complete thermodynamic description of the differences between standard vapor, crystal, solution, and soil-adsorbed states is possible. The results indicate that enthalpies and entropies of the solution and surface standard states are quite similar (though very different from the vapor state) resulting in a near-zero standard enthalpy difference and a small standard entropy increase for adsorption from solution. Considering naphthalene as a model for herbicides and as a probe into the nature of the soil surface, the results emphasize the importance of the unique structured nature of water acting as a solvent, and the competition of water for adsorption sites.

Effects of temperature, sunlight, soil incorporation and surface irrigation on the phytotoxicity of oryzalin (3,5-dinitro-N4,N4 -dipropylsulfanilamide) were studied. The activity of oryzalin applied 4 to 6 weeks prior to planting was enhanced by covering the soil with plastic as measured by the inhibition of grain sorghum [Sorghum bicolor (L.) Moench. 'Sexauer G-701′] root growth. Growth chamber studies demonstrated that oryzalin phytotoxicity to grain sorghum was greater at 20 and 25 C than at 30C. The control of foxtail millet [Setaria italica (L.) Beauv. #5 SETIT] bristly foxtail [Setaria verticillata (L.) Beauv. # SETVE], redroot pigweed (Amaranthus retroflexus L. # AMARE), and smooth pigweed (Amarantbus hybridus L.), and injury to grain sorghum increased as the thoroughness of mechanical incorporation of oryzalin into soil increased. The phytotoxicity of surface-applied oryzalin increased with increasing amounts of irrigation water until it equaled the level of a preplant-incorporated treatment.