The impact of a weevil (Rhinocyllus conicus Froel.) (Coleoptera: Curculionidae) on Carduus thistles in Virginia was evaluated in terms of seed reduction and viability during 1973 and 1974. Musk thistle (Carduus nutans L.) seed production from terminal and first lateral heads was reduced by 10% in 1973 and 75% in 1974 due to larval feeding of R. conicus. The greater seed reduction in 1974 was caused by heavy infestation (45% in 1973, 70% in 1974); there was a five-fold increase in the number of weevil pupation chambers per head over the previous year. Total seed production per plant decreased by 35 to 36% in both years despite increased plant vigor due to better growing conditions in 1974. Larval feeding reduced viability of mature musk thistle seeds. Although individual heads of plumeless thistle (Carduus acanthoides L.) were frequently destroyed by larval feeding, seed production from early heads of this thistle decreased by only 5% in 1973 and 4% in 1974 due to low rates of infestation (9% in 1973, 5% in 1974). Total seed reduction per plant for each of the two years was less than 0.2%. Infested heads of plumeless thistle did not produce sufficient seeds for evaluation of the weevil's impact on seed viability.

The uptake and distribution of 14C-bifenox [methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate] was different among corn (Zea mays L.), soybean (Glycine max (L.) Merr.) and velvetleaf (Abutilon theophrasti Medic.) following preemergence application to a greenhouse soil mix. Autoradiographs of seedlings harvested 14 days after treatment, showed the 14C to be in (or on) those areas of the crop plant in contact with the treated soil. Velvetleaf translocated 14C residue throughout the shoot. Absorption of 14C-compound(s) from treated nutrient solution accumulated in the roots of the three species but to a greater extent in soybean. There was no difference in the concentration of 14C in the shoots. However, in corn and soybean the 14C-compound(s) was confined to the primary and secondary leaf veins while velvetleaf showed a general distribution throughout the leaf tissue. Velvetleaf absorbed and translocated bifenox from shoot zones to a greater extent than the crop plants. Some acropetal movement was noted following leaf application to corn and velvetleaf but movement was only 3% of applied 14C from the treated leaf. No movement was detected in soybean.

Postemergence difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) for wild oat (Avena fatua L.) control in spring wheat (Triticum aestivum L.), durum wheat (Triticum durum Desf.), and barley (Hordeum vulgare L.) was evaluated in the field, greenhouse, and controlled environmental chamber. Wild oat control with difenzoquat was greater at the five- that at the three and one-half or two-leaf stages of growth. Barley tolerance to difenzoquat was excellent; however, spring wheat tolerance was influenced by cultivar. Durum wheat generally was more tolerant of difenzoquat than spring wheat. Tank mix combinations of broadleaf herbicides with difenzoquat had no effect on crop injury or wild oat control. Wild oat control with difenzoquat was greatest with adequate soil moisture, adequate fertility, warm air temperatures and high relative humidity. A simulated rainfall of 0.25 mm within ½ h or 1 mm within 4 h of application reduced wild oat control with difenzoquat.

EPTC (S-ethyl dipropylthiocarbamate) metabolism in corn (Zea mays L. ‘inbred B37’) was studied utilizing carbonyl-14C-EPTC and propyl-1-14C-EPTC. Two radioactive compounds were found in the organic-soluble fraction, namely, EPTC and EPTC-sulfoxide. Five metabolites were found in the water-soluble fraction. Amino acid analysis indicated that one water-soluble metabolite was a glutathione conjugate [S-(N,N-dipropylcarbamyl)glutathione] and that three other metabolites were probably degradation products of the glutathione conjugate. It was determined that EPTC-sulfoxide reacts chemically with reduced glutathione, yielding the conjugate. There was no detectable glutathione S-transferase enzyme activity associated with the sulfoxide cleavage.

Growth of sugarbeet (Beta vulgaris L. ‘Mono Hy A1’ and ‘Mono Hy D2′) and (B. patellaris Moq.) seedlings in cycloate (S-ethyl N-ethylthiocyclohexanecarbamate)-amended soil infested with the sugarbeet nematode (Heterodera schachtii Schmidt) was reduced (P = 0.05) at a concentration of 4 jug cycloate/g soil. Although the combination of cyloate with aldicarb [2-methyl-2-(methylthio) propionaldehyde-O-(methylcarbomyl) oxime] resulted in a significantly (P = 0.05) reduced growth of both sugarbeet cultivars and B. patellaris, it did not affect the nematicidal properties of aldicarb. Cycloate alone or in combination with aldicarb did not affect the growth of B. procumbens Chr. Sm. seedlings.

Germination of common mullein (Verbascum thapsus L.) in relation to constant and alternating temperatures, and light quality and duration was studied. In the dark, optimum germination occurred with 8-h warm periods of 30 to 40 C alternating with 16-h cold periods of 15 to 35 C. In the dark, no germination occurred below 10 C. With light during the 8-h warm periods, germination occurred at temperatures from 2 to 40 C, alternating with 0 C cold periods. The range of optimum temperatures for germination was also greatly expanded with light. Exposures to 24-h periods of red light, followed by incubation in the dark, produced the same germination response as 8 h of white light daily. Common mullein seeds germinated on the surface of the soil even though the seeds did not have mucilage.

Yellow nutsedge (Cyperus esculentus L.) tuber maturity was studied to determine its influence on accumulation of 14C from urea and NAA (naphthaleneacetic acid). Radioactive carbon from the above sources accumulated in tubers in decreasing amounts as tubers became more mature when the plants to which they were attached were treated. Tubers that were young at treatment accumulated the highest concentration of radioactivity and parent tubers (most mature) accumulated the least 14C. Tubers that were classified as mature, but not parents, accumulated insignificant amounts of radioactive carbon.

Herbarium records indicate that Russian pigweed (Axyris amaranthoides L.) entered the flora of Manitoba in 1886, spreading from there, by its own devices and by secondary introductions, to other provinces of Canada and to the United States. It is best established (to the extent of being considered a weed) in North Dakota and the prairie provinces of Canada.

Terbacil (3-tert-butyl-5-chloro-6-methyluracil) was applied to highbush blueberry plants (Vaccinium corymbosum L. ‘Pemberton’, ‘Rancocas', ‘Jersey’, and ‘Concord’) growing in a Rifle peat, Camas clay loam, or Mossy Rock silt loam for control of quackgrass [Agropyron repens (L.) Beauv.]. Control was 80 to 100% from applications made in April after the blueberry plants broke dormancy. Higher dosages proved phytotoxic from these applications on Camas clay loam. Applications in February or March while the blueberry plants were still dormant caused no phytotoxicit; to the blueberry plants and provided 80 to 90% quackgrass control. Four consecutive yearly applications caused no residual buildup to the point of phytotoxicity to blueberry plants. Carry-over of terbacil in the soil from year to year did occur.

Absorption and translocation of 14C-mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl] amino] phenyl] acetamide} in soybeans [Glycine max (L.) Merr. ‘Lee 68’], common cocklebur (Xanthium pensylvanicum Wallr.), and johnsongrass [Sorghum halepense (L.) Pers.] were evaluated under different environmental conditions with and without adjuvants. At a constant level of 40 or 100% relative humidity (RH), an increase in air temperature from 22 to 32 C resulted in a two- to three-fold increase in absorption and a four- to eight-fold increase in translocation of the 14C in soybeans following application to the second trifoliolate. At constant 22 or 32 C an increase from 40 to 100% RH resulted in less than a two-fold increase in absorption or translocation of 14C in soybeans. Autoradiograms indicated that movement of the 14C was primarily into leaves above the treated area. Translocation of 14C was significantly greater following application to the lower stem than to leaves. In common cocklebur, 14C absorption increased about three-fold at both 22 and 32 C with an increase from 40 to 100% RH following application to the second alternate leaf. At both levels of RH, absorption and translocation increased as the temperature was increased from 22 to 32 C. The addition of an adjuvant increased absorption and translocation in common cocklebur under all environmental conditions. When 14C-mefluidide was applied without an adjuvant to johnsongrass, absorption increased five- to six-fold at both 22 and 32 C as RH was increased from 40 to 100%. Translocation in johnsongrass was often affected less by variations in temperature than it was in soybeans or common cocklebur. The adjuvant increased absorption and translocation of the 14C-label of mefluidide in johnsongrass. The 14C-label accumulated primarily in the distal leaf of johnsongrass or in leaves above the treated area.

Annual herbicide treatments are usually necessary for acceptable control of grassy weeds in turfgrasses and it is important that repeated treatment do not injure the turf. Seven herbicides were applied annually for 4 yr at recommended and three times recommended rates to ‘Emerald’, ‘Meyer’, and ‘Matrella’ zoysia (Zoysia spp.) and three herbicides were applied annually for 3 yr at similar rates to Tifway′, ‘Tifgreen’, ‘Tifdwarf’ and ‘Ormond’ bermudagrass [Cynodon dactylon (L.) Pers.]. Herbicide treatments delayed early spring green-up of Emerald and Matrella slightly more than Meyer zoysia when compared with respective untreated checks. Four annual treatments of napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] and profluralin [N-(cyclopropylmethyl)-a,a,a-trifluoro-2, 6-dinitro-N-propyl-p-toluidine] reduced the cover of Meyer more than Emerald or Matrella when final ratings were made. The 10.1 kg/ha rate of prosulfalin {N-[[4-(dipropylamino)-3,5-dinitrophenyl] sulfonyl]-S,S-dimethylsulfilimine} and benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) also reduced the cover of Meyer. Profluralin at 10.1 kg/ha was the only treatment that reduced the stand of Matrella and none of the treatments reduced the stand of Emerald. The 10.1 kg/ha treatments of profluralin and prosulfalin reduced the stand of Tifgreen, Tifdwarf, and Ormond more than Tifway bermudagrass. None of the herbicide treatments reduced the stand of Tifway.

Root uptake and translocation of nitrofluorfen [2-chloro-1-(4-nitrophenoxy)-4-(trifluoromethyl)benzene] and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] were measured in fababean (Vicia faba L.) and green foxtail [Setaria viridis (L.) Beauv.] plants, and metabolism was studied using fababean leaf discs and green foxtail leaf segments. Both herbicides were taken up readily from nutrient solution but translocation was limited. In fababeans, 4.6% of the nitrofluorfen label was translocated to the shoot as compared to 2.2% of the oxyfluorfen label. Less than 10% of the nitrofluorfen or oxyfluorfen taken up in vitro was metabolized after 24 h. This rate of metabolism would not likely influence the herbicidal action of either herbicide.

Several differences between the mode of action of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) and triallate [S-(2,3,3-trichloroallyl)diisopropylthiocarbamate] were observed on wild oats (Avena fatua L.) in growth chamber experiments. Trifluralin exhibited little or no postemergence effect when applied to the soil surface. Surface applications of triallate interfered with deposition of epicuticular wax on leaf surfaces, and caused necrotic lesions, leaf break, and the abortion of the first leaf through the coleoptile. Trifuralin, but not triallate, incorporated in the soil reduced extension of the wild oat coleoptile. Soil-incorporated treatments involving trifluralin induced more extensive swelling of the mesocotyl, coleoptile node, and and coleoptile than triallate applied similarly. Triallate appeared to exert its major effect on cell elongation of the wild oat foliar material enclosed in the coleoptile. Trifluralin caused its greatest phytotoxic effect on the meristematic tissue at the region of the coleoptile node.

Glyphosate [N-(phosphonomethyl)glycine] and EPTC (S-ethyl dipropylthiocarbamate) did not reduce significantly the percent germination of either ‘Saranac’ or ‘Vernal’ cultivars of alfalfa (Medicago sativa L.) grown in petri dishes. Glyphosate at 10−5 M significantly reduced shoot length of both cultivars. Vernal alfalfa appeared to be more susceptible to glyphosate than the Saranac cultivar. Soil applications of glyphosate also had no effect on percent emergence of either cultivar and reduced plant height only of Vernal when applied to the soil at 17.9 kg/ha. Applications of glyphosate at 2.2, 4.5, and 9.0 kg/ha to a Kentucky bluegrass (Poa pratensis L.) sod in a simulated sod seeding alfalfa establishment study in the greenhouse reduced dry weight of both alfalfa cultivars; Vernal was affected more adversely than Saranac. Application of 2.2 kg/ha glyphosate in four management systems showed that a 3-day planting delay after spraying reduced growth inhibition of alfalfa seeded in treated sod. These results were similar to those obtained with paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) in these management systems. Kentucky bluegrass clippings treated with paraquat 3 days or less before contact with alfalfa seedlings significantly reduced seedling dry weight. Clippings treated with glyphosate did not reduce alfalfa seedling dry weights significantly.

The effect of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], desmedipham [ethyl m-hydroxycarbanilate carbanilate(ester)], propanil (3′,4′-dichloropropionanilide), and dibromothymoquinone (DBMIB) (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone) on proton translocation and photophosphorylation in isolated spinach (Spinacia oleracea L.) chloroplast fragments was investigated. In the absence of added cofactors, O2, or artificial electron acceptors, cyclic electron transport occurred, which was coupled to energy conservation. Under aerobic conditions O2 acted as the terminal acceptor in non-cyclic electron transport. Proton translocation and photophosphorylation in the cyclic process were enhanced by diuron, desmedipham, and propanil, while in the non-cyclic process they were inhibited by all three herbicides. DBMIB inhibited proton translocation and photophosphorylation in both processes. Proton translocation and its enhancement increased with increasing light intensities. The finding that the plastoquinone (PQ) antagonist DBMIB disrupted cyclic as well as noncyclic electron flow, while diuron enhanced the cyclic and inhibited the noncyclic process, indicated that the acceptor site for endogenously-cycling electrons must lie between the active site of diuron inhibition and PQ, The close similarity in the behavior of diuron, desmedipham, and propanil suggests that their site of action is the same.

No differences in the anatomy or bud pattern development were observed between young tap and lateral roots of rush skeletonweed (Chondrilla juncea L.). Shoots and lateral roots arise from meristemic zones that originate from a continuous pericyclic ring. Incubation of excised root segments resulted in rapid development of stem buds which showed geotropic response in 24 h. The development of identifiable leaf initials occurred prior to emergence through the epidermis in 8 days.

Nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] are 2 diphenylether herbicides which are phytoactive on common purslane (Portulaca oleracea L.). The stomata of common purslane are normally open during the day and closed at night. Nitrofen and oxyfluorfen applications to common purslane leaves cause the stomata to close which is a result of increased membrane permeability. A slight increase (0.6 C) in leaf temperature and a decrease (2 bars) in the apparent water potential was evident after 6 h. Membrane degradation caused some cells to collapse and caused the leaves to appear pitted. Ethylene synthesis was stimulated (0.9 ppmv) causing a loss of plastids from the bundle sheath cells and finally leaf abscission, 8 to 24 h after treatment.

In order to germinate successfully, large crabgrass [Digitaria sanguinalis (L.) Scop.] seeds require a period of after-ripening. Some changes, either physical, biochemical or both, must occur in these seeds during this after-ripening process. This paper reports the differences in the activities of several enzymes between dormant (non-after-ripened) and nondormant (after-ripened) large crabgrass seeds at various periods of hydration. The total protein content of dormant seeds does not change during imbibition but increases greatly in nondormant seeds at 48 and 76 h of hydration. Initially, nondormant seeds exhibit high alpha-amylase activity and low peroxidase and acid phosphatase activities. Alpha-amylase activity remains unchanged relatively in both dormant and nondormant seeds up to 36 h of hydration, but increases greatly in nondormant seeds at 48 and 76 h of hydration. Peroxidase activity, which is initially low in nondormant seeds, increases substantially at 48 and 76 h of soaking. Acid phosphatase activity in dormant seeds does not change following hydration but is gradually elevated in nondormant seeds with duration of soaking. Lipase activity in dormant seeds remains fairly constant upon hydration. In nondormant seeds, however, the activity gradually decreases with duration of soaking, the decrease being 3 to 4 fold at 76 h of imbibition. Except for lipase, there is a positive correlation in the activities of alpha-amylase, peroxidase, and acid phosphatases with the increase of total protein content of nondormant seeds.

R-25788 (N,N-diallyl-2,2-dichloroacetamide) had no effect on 14CO2 evolution from carbonyl-14C-EPTC (S-ethyl dipropylthiocarbamate) treated corn (Zea mays L. ‘inbred Oh551’). Treatment with 1.0 ppmw R-25788 increased production of water-soluble and unextractable products from EPTC and increased the rate of disappearance of organic-soluble radioactivity. R-25788 increased levels of reduced and oxidized glutathione in corn roots. Pretreatment of corn in nutrient solution with R-25788 had no effect on glutathione synthetase activity in root tissue, but R-25788 at 5.0 and 500.0 nM showed an in vitro stimulation of the enzyme.

Some genetic and physiological aspects of seed germination of wild and weedy sunflowers were investigated in order to analyze their population differentiation in seed characteristics. Seed germination of six populations classified on the basis of morphology as Helianthus exilis Gray, H. exilis-bolanderi hybrids, and H. bolanderi Gray was studied under red light at 20 C. The average germination of the three groups respectively were 56, 63, and 42%. Germinability of individual plant progenies derived from populations of H. bolanderi and H. exilis was studied under red and far-red light combined with the pretreatments at two temperatures (10 and 20 C). Average germination per progeny reached a maximum of 59% with red light and 10 C in H. bolanderi. Far-red light promoted germination of H. bolanderi but was ineffective with H. exilis. The homogeneity of populations within each taxon and the fact that germinability differences among the H. bolanderi progenies were consistent over replications, suggest a genetic component of variation. However, progenies obtained by crossing selected individuals that germinated under certain light and temperature treatments, were not significantly correlated in germinability with that of their parents. Inheritance of germination characteristics appears to be complex and highly dependent on the environmental conditions.