The influence of some s-triazine herbicides on acid phosphatase (acid Pase) and phosphodiesterase (PDase) from corn (Zea mays L. var. ‘Orfeo’) roots was investigated. Terbutryn [N-(1,1-dimethylethyl)-N′-ethyl-6-(methylthio)-1,3,5-triazine-2,4-diamine] stimulated both phosphatases, whereas prometryn [N,N′-bis(1-methylethyl)-6-(methylthio)-1,3,5-triazine-2,4-diamine] stimulated only the PDase. Atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] and desmetryn [N-methyl-N′-(1-methylethyl)-6-(methylthio)-1,3,5-triazine-2,4-diamine] inhibited both phosphatases to varying degrees. Atraton [N-ethyl-6-methoxy-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine], prometon [6-methoxy-N,N′-bis(1-methylethyl)-1,3,5-triazine-2,4-diamine], and simazine (6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine) inhibited acid Pase. No effect was exerted by ametryn [N-ethyl-N′-(1-methylethyl)-6-(methylthio)-1,3,5-triazine-2,4-diamine]. The enzyme assays and the kinetic parameters demonstrated that the interferences observed were due to an action on the synthesis of one or both enzymes rather than on the enzyme reactions. The types of the N-alkyl and the C1-substituent groups in the structures of the s-triazines tested appear important in determining the degree of the interference.

Absorption and translocation of glyphosate [N-(phosphonomethyl)glycine] with and without adjuvants were examined in field bindweed (Convolvulus arvensis L. # CONAR) to develop an understanding of the influence of selected adjuvants and environment before application on glyphosate activity. Light intensity and humidity during plant development resulted in differences in 14C-glyphosate absorption. When applied in water or with an oxysorbic (20 POE) (polyoxyethylene sorbitan monolaurate) adjuvant, an average of 9% of the glyphosate was absorbed in plants grown in high light intensity, low humidity (HLLH) before treatment, compared to an average of 21% in plants grown in low light, high humidity (LLHH) before treatment, respectively. Amounts of epicuticular wax on HLLH field bindweed were almost three times as great as on LLHH leaves and may explain absorption differences. No differences in glyphosate absorption were observed between glyphosate applied with oxysorbic or no adjuvant even though the oxysorbic adjuvant effectively reduces surface tension. Absorption was increased two- to threefold with a polyethoxylated tallow amine adjuvant (MON 0818) compared to no adjuvant. Unlike absorption without adjuvant or with oxysorbic adjuvant, there were few absorption differences in plants grown in different environments before application. Absorption continued for 24 to 36 h after application regardless of adjuvant. Reductions in MON 0818 concentration and subsequent necrosis resulted in increased movement of radioactivity away from the site of application.

To develop an understanding of how adjuvants might enhance glyphosate [N-(phosphonomethyl)glycine] activity, absorption and translocation of a polyethoxylated tallow amine amphoteric surfactant (MON 0818) were examined in field bindweed (Convolvulus arvensis L. # CONAR). Scanning electron microscopy did not reveal any physical disruption of the epicuticular waxes from spray applications of MON 0818, an oxysorbic (20 POE) (polyoxyethylene sorbitan monolaurate) surfactant, or glyphosate. Radioactive MON 0818 absorption was rapid during the first 6 h. Maximum absorption (84%) occurred by 24 h after application. Less than 3% of the applied radioactivity was recovered from the epicuticular wax of treated leaves. Movement of radioactivity away from the treated area was limited predominantly to movement within the treated leaf. Altering light intensity or humidity in which the plants developed before treatment did not influence MON 0818 absorption.

Hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] toxicity, absorption, translocation, metabolism, and effect on photosynthesis were investigated with rooted cuttings of highbush blueberry (Vaccinium corymbosum L.), rabbiteye blueberry (V. ashei Reade), and hollow goldenrod (Solidago fistulosa Miller # SOOFI). Highbush and rabbiteye blueberry plants were three times more tolerant to root applications of hexazinone than hollow goldenrod. Blueberry plants absorbed an average of 7.9% of root-applied 14C-hexazinone and hollow goldenrod absorbed an average of 10.1%. An average of 6.8% of root-absorbed hexazinone (14C-label) was translocated from the roots of blueberry to stem and leaves. Radioactivity in hollow goldenrod was distributed equally between roots and shoots. The majority of radioactivity in both species was recovered as hexazinone. Root-absorbed hexazinone caused a rapid inhibition of photosynthesis in intact hollow goldenrod leaves. Root-absorbed hexazinone was capable of inhibiting photosynthesis in intact blueberry leaves; however, this occurred only when roots were exposed to high concentrations of hexazinone.

In a 2-yr field study, selective application of a 2.5% (v/v) solution of the ammonium salt of fosamine [ethyl hydrogen(aminocarbonyl)phosphonate] plus 0.5% (v/v) nonionic surfactant to multiflora rose (Rosa multiflora Thunb. # ROSMU) demonstrated leaves to be the major site of uptake for suppressing growth. In greenhouse studies, 14C-fosamine was absorbed in decreasing order by axillary bud, leaf, and stem treatments, respectively. 14C was rapidly translocated throughout multiflora rose plants when applied to leaf, stem, or bud tissue. The highest 14C concentration always occurred at the site of uptake. In a 32-day study, the treated leaf, the treated bud, and treated stem had the highest 14C concentration when 14C-fosamine was leaf, bud, or stem applied, respectively.

In laboratory experiments, the safener CGA-92194 {α-[(1,3-dioxolan-2-yl-methoxy)imino] benzeneacetonitrile} increased the in vitro chemical reactivity of the herbicide metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] for glutathione (GSH) when tested at 1, 50, and 100 μM. Pretreatment of sorghum [Sorghum bicolor (L.) Moench. cv. ‘G623’] seeds with the safener CGA-92194 (1.25 g ai/kg of seeds) enhanced significantly the amount of 14C-metolachlor absorbed by the roots and translocated to the shoots and leaves of grain sorghum seedlings grown hydroponically in a nutrient solution. Thin-layer chromatographic analysis of methanol-soluble extracts from roots or shoots and leaves of sorghum seedlings treated with 14C-metolachlor revealed the detection of 8 to 10 metabolites of this herbicide. One of the major metabolites detected was tentatively identified as the conjugate of metolachlor with GSH. A safener-induced stimulation of metolachlor metabolism via conjugation to GSH was observed in sorghum seedlings grown from seeds pretreated with CGA-92194. Addition of tridiphane [2-(3,5-dichlorophenyl)-2-(2,2,2-trichloroethyl)oxirane], a potent inhibitor of plant GSH-S-transferase enzymes, to the nutrient solution of hydroponically grown sorghum seedlings reduced the formation of GS-metolachlor in both control and safener-treated seedlings and minimized the stimulatory effect of the safener CGA-92194 on the conjugation of metolachlor to GSH. It is suggested that the safener CGA-92194 may protect grain sorghum against injury from the herbicide metolachlor by stimulating the spontaneous and enzymatic conjugation of this herbicide with GSH.

Akinetes (spores) of the green, filamentous alga Pithophora oedogonia (Montagne) Wittrock were more copper resistant than filamentous cells, tolerating copper concentrations as high as 4 μg·ml-1 (16 μg·ml-1 copper sulfate pentahydrate). The localization of copper in viable and nonviable cells was conducted using cell fractionation and cytochemical/ultrastructural methods. In copper-exposed viable akinetes, copper was bound primarily to the outer layers of the cell wall. In nonviable cells, copper was found randomly distributed throughout the cytoplasmic and vacuolar regions. No evidence for compartmentation of copper as vacuolar or intranuclear deposits was demonstrated. Copper uptake into the cell wall was associated with release of equimolar amounts of calcium, magnesium, and zinc. When viable copper-treated akinetes were allowed to recover in copper-free medium, the copper was gradually released from the cell wall, presumably to the culture medium. A portion of the copper also appeared to be redistributed to new cell wall material during the akinete germination process. The differential tolerance of P. oedogonia akinetes to copper in comparison to filamentous cells appears to be due to a combination of factors that include cell surface/volume ratios, metabolic activity, and cell wall copper-binding components.

Partially purified glutathione-s-transferase (GST) isolated from corn (Zea mays L.) seedlings was about 14-fold higher in specific activity than GST isolated from giant foxtail (Setaria faberi Herrm. # SETFA) seedlings. Greater amounts of GST activity were present in leaf tissue than in stem tissue. Four-leaf giant foxtail seedlings contained about threefold more reduced glutathione per gram fresh weight in the leaves than one- to two-leaf giant foxtail seedlings. When atrazine and reduced glutathione were used as substrates, tridiphane [2-(3,5-dichlorophenyl)-2-(2,2,2-trichloroethyl)oxirane] inhibited isolated GST from corn with an I50 of about 5 μM and from giant foxtail with an I50 slightly lower. Tridiphane inhibited the metabolism of atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] to water-soluble metabolites in giant foxtail leaves but not in corn leaves. Unmetabolized atrazine levels tended to be greater in giant foxtail seedlings treated with tridiphane plus atrazine than in plants treated with atrazine alone. Tridiphane applied 12 h before atrazine increased the uptake of atrazine in both corn and five-leaf giant foxtail seedlings. The amount of atrazine metabolism to water-soluble metabolites increased in corn leaves but remained constant in giant foxtail leaves when atrazine uptake was increased. Tridiphane and atrazine combinations impaired net photosynthetic rates more than atrazine alone in giant foxtail seedlings but did not increase chlorophyll fluorescence. There was no decrease in net photosynthetic rate 12 h following applications of atrazine or tridiphane plus atrazine on corn leaves. Tridiphane did not decrease photosynthesis or increase chlorophyll fluorescence in either species when applied alone.

The germination of caryopses on water or GA3 solutions was used to characterize the degree of primary dormancy present in the seed progeny of 10 genetically pure lines of wild oats (Avena fatua L. # AVEFA). These 10 lines represented a range of types from lines exhibiting no dormancy to those with a high degree of dormancy. Repeated propagation of these pure lines under constant environmental conditions identified several genetically inherited characters that were associated with the inherited differences in degree of primary dormancy. Correlation of the seed development period, number of primary caryopses produced, and caryopsis moisture content to the degree of primary dormancy shows: a) Lines characterized by low degrees of primary dormancy were, in general, those that had a short seed development time and produced few heavy seed low in percent water; and b) lines characterized by high degrees of primary dormancy were, in general, those that had a long seed development time and produced many light seed high in percent water. The adaptive advantage of the coupling of physiological and morphological characters with degree of dormancy is discussed and the possibility that some characters are determined by others is indicated.

Percent germination and germination rates of seeds of atrazine (6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine)-resistant and -susceptible biotypes of redroot pigweed (Amaranthus retroflexus L. # AMARE) and Powell amaranth (A. powellii S. Wats. # AMAPO) from southern Ontario were compared in petri dishes using a 100-cell germination plate. The plate provided 100 separately controlled, alternating temperature combinations ranging from 0 to 45 C in increments of 5 C. The experiment was conducted under alternating light and dark conditions for 21 days and under constant dark conditions for 7 days. Initial seed viabilities exceeded 90% for all four biotypes. Under alternating light and darkness, the resistant biotype of Powell amaranth had significantly lower total germination and a slower rate of germination than the susceptible biotype, whereas the biotypes of redroot pigweed did not differ in germination response. Germination rate and total germination were positively correlated for all four biotypes. In constant darkness, the atrazineresistant biotypes of both species had significantly lower germination percentages compared to the susceptible biotypes. In general, percent germination of Powell amaranth was greater than that of redroot pigweed for day and night temperatures <25 C, whereas redroot pigweed had greater germination at higher temperatures. Greater seed dormancy of the resistant biotypes under some light and temperature combinations may have implications for the persistence of resistant populations in the field.

Giant foxtail (Setaria faberi Herrm. # SETFA) seed germination was about 55% in water but increased to >90% after pretreatment in polyethyleneglycol 8000 (PEG) at water potentials of −0.3 MPa or less. Pretreatment at 20 C required about 24 h exposure to PEG for maximum effect, but at 35 C shorter times (4 to 8 h) gave a partial effect. Treatment with PEG can begin at the time of seed wetting or after the seeds have imbibed water for 24 h. Continuous exposure to a water potential of −0.5 MPa PEG (or less) imhibited germination. Other methods of applying temporary water stress to the seeds, such as slow hydration in a humid atmosphere, or drying after partial hydration, increased germination in a manner similar to PEG treatment. The relatively slow response kinetics with PEG suggest that increased germination was caused by physiological adaptation to water stress, possibly by observed adjustments in seed water potential. It is suggested the water stress mechanism could operate under field conditions where wetting-drying cycles are common.

Texas panicum (Panicum texanum Buckl. # PANTE) is a native of the Southwest, now increasing as a weed throughout the southern United States, whereas wild proso millet (Panicum miliaceum L. # PANMI) is an introduced weed currently increasing in importance in the northern Midwest. In controlled-environment chambers, both species produced more tillers, greater leaf area, and more total dry weight at 30/24 C day/night (simulated growing season temperature in Georgia) than at 24/18 C (simulated growing season temperature in Minnesota). Texas panicum accumulated more dry matter at 30/24 C than did wild proso millet, while wild proso millet accumulated more dry matter at 24/18 C than did Texas panicum. When the two species were grown together, Texas panicum was the superior competitor at 30/24 C while wild proso millet was superior at 24/18 C. Exposure to short photoperiods at an intermediate temperature of 27/21 C accelerated flowering and limited vegetative growth in both species. In the range of photoperiods (10 to 16 h) examined, wild proso millet always flowered earlier and, consequently, produced less vegetative growth than Texas panicum. Its responses to temperature and photoperiod indicate that wild proso millet probably would be competitively inferior to Texas panicum and other adapted grass weeds in the southern United States.

Teliospores of Sphacelotheca holci Jack. [= S. cruenta (Kuhn.) Potter] infected johnsongrass [Sorghum halepense (L.) Pers. # SORHA) systemically after inoculation of cut stems in greenhouse studies. A preliminary host range test in the greenhouse revealed that no infection occurred on four varieties of sorghum (S. vulgare L.) and three cultivars of sudangrass (S. Sudanese L.). Infected johnsongrass plants grown in the greenhouse exhibited reduced vegetative growth and altered morphological characteristics compared to healthy johnsongrass plants. The aboveground biomass and lateral rhizome expansion of smutted johnsongrass field transplants were significantly lower than that of uninfected plants. Significant correlations between fraction of johnsongrass stems infected and plant weight, and basal area of plants were observed in field studies. Corn (Zea mays L.) and alfalfa (Medicago sativa L.) grown in competition with johnsongrass, and johnsongrass infected with S. holci reduced the aboveground biomass and rhizome length of johnsongrass plants significantly, compared to that of uninfected johnsongrass plants grown alone in greenhouse studies. Uninfected johnsongrass plants also exhibited higher plant weight than infected plants when both were grown in competition with alfalfa, regardless of the alfalfa planting density in the greenhouse or when measured after 3 months in field trials.

Clods of three sizes (1.5-, 3.3-, and 5.3-cm diameter) and two hardnesses [soft (0.3 MPa) and hard (2.2 MPa)] were made by incorporating seed from one of the five following weed species: corn poppy (Papaver rhoeas L. # PAPRH), shepherdspurse [Capsella bursa-pastoris (L.) Medic. # CAPBP], smooth crabgrass Digitaria ischaemum (Schreb.) Muehlenb. # DIGIS], common lambsquarters (Chenopodium album L. # CHEAL), and Canada thistle [Cirsium arvense (L.) Scop. # CIRAR], listed by increasing seed size. Under conditions of this experiment, higher germination occurred with larger seed. The higher germination was connected with fewer dormant seed remaining in the clods. Germination significantly decreased (13%) in the larger soft and hard clods with the smaller seed sizes (less germination associated with more dormant seed remaining in the clod). Germination of the two larger seed decreased (23%) only in the larger soft clods but was less significant with both small seed. Non-emerged seedlings increased with larger clods and was most significant with the three large seed in the hard clods and absent with the three large seed in the soft ones. On the average, 70% of the germinated seed emerged. Differences in germination as well as in nonemerged seedlings caused decreased emergence on larger clods. Clod influence in germination and emergence was explained by the volumes of the clod layers involved, and in some comparable aspects corresponded with volumes (depths) of soil layers.

The effects of tobacco thrips (Frankliniella fusca Hinds) control and herbicides on peanut (Arachis hypogaea L. ‘Florigiant’) canopy development and competition with large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA] were examined in field experiments during 1983 and 1984. Greater early-season peanut canopy development generally occurred when tobacco thrips were controlled with aldicarb [2-methyl-2-(methylthio) propionaldehyde-O-(methylcarbamoyl)oxime]. Tobacco thrips control did not affect large crabgrass dry weights or peanut seed yields with no herbicide, alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide], vernolate (S-propyl dipropylcarbamothioate) + benefin [N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine] + alachlor, and handweeding + sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio) propyl]-3-hydroxy-2-cyclohexen-1-one}. Averaged across weed control levels, large crabgrass dry weights with and without aldicarb were 320 and 310 g/m2 in 1983, and 260 and 250 g/m2 in 1984, respectively. Peanut seed yields with and without aldicarb were 1550 and 1630 kg/ha in 1983, and 2870 and 2920 kg/ha in 1984, respectively.

A 2-yr field study was conducted to measure the growth and development of Russian thistle (Salsola iberica Sennen and Pau # SASKR) in the growing crops of winter and spring wheat (Triticum aestivum L.) and after harvest of these crops. In herbicide-free conditions, few Russian thistle seedlings emerged in winter wheat. Only 50% of these plants survived compared to 92 and 95% survival in spring wheat and crop-free treatments, respectively. Compared to growth in the crop-free treatment, both wheat types suppressed oven-dry weight, height, and width of Russian thistle plants during the crop-growing season and after crop harvest. During the crop-growing season, winter wheat suppressed Russian thistle height and width more than spring wheat. After crop harvest, oven-dry weight of Russian thistle plants grown in winter wheat stubble was suppressed 75% compared to plants grown in spring wheat stubble. Russian thistle plants grown in crop-free, spring wheat, and winter wheat treatments produced 152 100, 17 400, and 4 600 seeds/plant, respectively.

Ivyleaf morningglory [Ipomoea hederacea (L.) Jacq. # IPOHE], planted in 1984 and 1985 the first of each month from April through August, began emerging in cotton (Gossypium hirsutum L. ‘Acala SJ-2’) 1 week after planting. Morningglory, at a density of 1 plant/2 m of row, emerging in April and May became so competitive to cotton by harvest in September that the total crop was lost. June plantings, although less competitive than earlier plantings, still reduced yields by 11%. Later plantings did not reduce yields of cotton. Morningglory plantings that produced seed (April through July) began flowering within 7 weeks, and viable seed was collected for the first time 9 weeks after planting. Ivyleaf morningglory plants that emerged in April and May produced about 11 000 seed/plant by cotton harvest. This compared to 3000 and 93 seed/plant for morningglory that emerged in June and July, respectively. The earliest that morningglory might be expected to produce seed in cotton planted in early April would be late May to early June, and morningglory emerging as late as the first of July could produce some seed by cotton harvest.

The weedy spurges found in the Delta region of Mississippi, U.S.A., include spotted spurge (Euphorbia maculata L. # EPHMA), nodding spurge (Euphorbia nutans Lag. # EPHNU), prostrate spurge (Euphorbia humistrata Engelm. ex Gray # EPHHT), creeping spurge (Euphorbia serpens H.B.K. # EPHSN), and hyssop spurge (Euphorbia hyssopifolia L. # EPHHS). Nodding spurge was the most common while creeping spurge was the least common. Hyssop spurge, not previously known to be in Mississippi, was found in six of the 17 counties in the Delta of Mississippi. Hyssop spurge occurs with, and had previously been confused with, nodding spurge. Diagnostic characters, special identification features, and illustrations are provided to aid in identification of these five species of weedy spurges, which occur widely in the U.S.

Integration of preplant-incorporated molinate (S-ethyl hexahydro-1H-azepine-1-carbothioate) at 4.5 kg ai/ha and a brief postseeding drainage period in water-seeded rice (Oryza sativa L.) gave the best red rice (Oryza sativa L. # ORYSA) control without a significant reduction in cultivar stand density. This combination of practices provided higher cultivar grain yield and lower red rice grain yield than any water management practice alone. Continuous-flood water management provided a substantial reduction in red rice stand density, but it also caused a significant reduction in the cultivar stand density. Under the reduced stand density conditions, the red rice was very competitive and yielded more than the cultivar. Although brief drainage alone gave a significantly lower level of red rice control, it had no significant effect on the cultivar stand density, and the red rice and cultivar yields were not significantly different from the continuous-flood yields. Prolonged drainage had the highest red rice and cultivar stand densities and the highest red rice grain yield, but the cultivar yield was not significantly different from the other plots that were not treated with herbicide. Although this treatment gave the highest total grain yield, its composition had the highest percentage of red rice. Puddling the seedbed did not alter the stands or yields of red rice or cultivar compared to the nonpuddled plots with the same water management and herbicide rate. The application of molinate as a preplant-incorporated treatment or as a preplant postflood treatment before or after puddling gave results that were not significantly different from each other. The superior performance of preplant application of molinate in water-seeded rice in conjunction with a brief postseeding drainage period provides an excellent tool for red rice suppresion.

The potential for yellow nutsedge (Cyperus esculentus L. var. leptostachyus Boeck. # CYPES) regrowth was reduced by increasing plant age and by glyphosate [N-(phosphonomethyl)glycine] and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene]. Of the amount of glyphosate transported to underground parts, most was found in the tubers, with immature rhizomes, roots, and tubers having 2 to 3 times higher concentrations than comparable mature tissues. Addition of unlabeled oxyfluorfen as a tank mixture with glyphosate increased absorption and translocation, mainly into leaves and new tubers, of radioactivity from 14C-glyphosate in 30-day-old plants. In contrast to the younger plants, the addition of oxyfluorfen decreased 14C-glyphosate detected in 60-day-old plants. The greater effectiveness of glyphosate when applied with oxyfluorfen on yellow nutsedge at the early growth stage has important implications in the field because the tuberization process must be stopped early in the development of the plant for successful control.