Freshly-harvested seeds of several common weeds showed little or no promotion of germination by light. However, after burial for 6 months, germination becomes entirely dependent on exposure to light. Red light promoted the germination of the buried seeds, and this promotion was reversed by far-red light, indicating phytochrome involvement. Freshly-harvested seeds were made light-requiring by treatment with mannitol. The germination of these light-requiring seeds was promoted by red light, gibberellic acid (GA), acetylcholine (ACh), and adenosine 3′,5′-monophosphate (cyclic AMP). The phytochrome response may trigger ACh synthesis which causes the release of GA from a bound form and/or GA synthesis which enhances the production of cyclic AMP which initiates the germination response.

Reserve carbohydrates of Dalmatian toadflax (Linaria dalmatica (L.) Mill.) in eastern Washington were at their highest levels in autumn at the end of the growing season, and the lowest point occurred at the beginning of flowering about June 15. A one-time removal of first-year floral stems (June 11, 1964) did not significantly lower reserve carbohydrates when measured in September, but similar clipping of floral stems the second year (June 16, 1965) did cause a significant reduction. Reserves were reduced by 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) at 1.12 or 1.68 kg/ha but were not reduced by 4-amino-3,5,6-trichloropicolinic acid (picloram) at the same rates. Combinations of equal weights of the two herbicides to total 1.12 or 1.68 kg/ha caused a significant reduction in reserve carbohydrates. The combinations of silvex and picloram appeared to have an additive toxic effect, but the reduction of reserve carbohydrates was no greater than that caused by silvex alone at 1.12 or 1.68 kg/ha. Lethal action of the herbicides did not appear to be caused by reserve carbohydrate depletion. Glucose and fructose were the major reducing sugars detected in chromatographic analysis.

A liquid scintillation counting solution was developed which optimized the direct assay efficiencies of 14C-labeled 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 3,6-dichloro-o-anisic acid (dicamba), and α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) in soil. In this counting technique, 3-g soil samples containing 14C-labeled herbicide were placed directly into a liquid scintillation vial containing a phosphorescent counting solution. Samples were shaken and allowed to settle before assaying using a liquid scintillation spectrometer. This direct radioassay was as efficient or more efficient than double or single extraction processes. Automatic external standardization in conjunction with the liquid scintillation counter was an effective tool for estimating the 14C present in soil samples.

Shoot apices of 7-day old foxtail millet (Setaria italica (L) Beauv.) seedlings treated with 2 and 20 mg/L of dimethyltetrachloroterephthalate (DCPA) were examined under the electron microscope. Cell division is interrupted. The nucleus and nucleolus do not disintegrate and chromosomes do not differentiate. Instead, giant nuclei and giant nucleoli occupy most of the cell volume in the meristematic regions. Several nucleolar caps form on the giant nucleolus; and in the advanced stages, they separate and are encircled by a nuclear membrane to form multiple nuclei. Other organelles are also affected. Cristae and thylakoid membranes of mitochondria and chloroplasts degenerate and multiple vacuoles form. Cell walls are markedly more osmophilic after DCPA treatment. Treated cells are less turgid than controls.

The foliar uptake of 4-amino-3,5,6-trichloropicolinic acid (picloram) and its phytotoxicity in mixtures with several phenoxy herbicides were studied using bean (Phaseolus vulgaris L. ‘Red Kidney’). The greatest accumulation of picloram occurred in the growing point, stem, and axillary buds. Transport from the treated leaf occurred within 6 hr and continued for at least 7 days. The effectiveness of herbicide combinations containing picloram was related to the particular plant part measured. A synergistic reduction in fresh and dry red kidney bean weight was obtained with (2,4-dichlorophenoxy) acetic acid (2,4-D) or 2-[(4-chloro-o-tolyl)oxy]propionic acid (mecoprop) when applied in combination with picloram, whereas 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) and picloram gave an antagonistic response. An investigation of the antagonistic reaction of 2,4-DB with picloram indicated that picloram prevented the movement of 2,4-DB, while 2,4-DB increased both the distribution and the amount of picloram translocated from the point of application.

The leaching of α,α,α-trifluoro-2,6-dinitro-N,N,-dipropyl-p-toluidine (trifluralin) and 3,5-dinitro-N4,N4-dipropylsulfanilamide (oryzalin) with and without surfactants was studied in soil columns. In dry soil without surfactants leaching of trifluralin was less than that of oryzalin and did not amount to more than a few centimeters despite the use of light soil and large amounts of herbicide. In wet soil trifluralin leached more than twice as deep as in dry soil with the same amount of water. The addition of surfactants at a concentration of 2% of the spray volume increased both depth of water penetration and herbicide movement into the soil. The most pronounced effect of surfactants was the increase in movement of trifluralin in dry soil, but they also increased trifluralin movement in wet soil. There was no direct relationship between the ability of the surfactants to improve water penetration and their effects on leaching of the two herbicides. It was therefore concluded that increased leaching was due to an effect of surfactants on the sorption-desorption balance rather than on improved penetration of water. The improved movement of trifluralin into the soil as a result of surfactant action was also evident from another experiment in which surfactants increased the herbicidal activity of trifluralin sprayed preemergence on the soil surface.

Microscopic examination of central and soft offset bulbs of wild garlic (Allium vineale L.) at senescence of the parent plants in May and June revealed embryonic plants with numerous root primordia and four or five shoot primordia. Hardshell bulbs and aerial bulblets contained only one or two root primordia and three leaf primordia. The embryonic plants of central, soft offset, and hardshell bulbs elongated slowly during the after-ripening period. Rapid cell division, cell elongation, and initiation of new leaves took place after termination of the after-ripening period in all but the dormant hardshell bulbs. In November, new hardshell bulbs could be seen at the base of plants developed from central and soft offset bulbs.

Flooding soil with 5 to 10 cm of water for 7 to 14 days killed all freshly planted johnsongrass (Sorghum halepense (L.) Pers.) rhizomes in greenhouse and field experiments. A delay in flooding until culms emerged greatly reduced control. Flooding the soil in which 4-week-old johnsongrass plants grew had little effect at 15 C, but plants were killed after 8 weeks of flooding at 40 C. Death of buds on immersed johnsongrass rhizomes occurred more rapidly at 40 C than at 10, 20, 25, or 30 C. Flooding for 8 days at 40 C killed all rhizomes, but 16 days of flooding were required to kill all rhizomes at 30 C. Few buds were killed when flooded at 10 or 20 C, but germination was delayed. Immersing rhizomes in water and soil provided better control than immersing them in water without soil.

Cottonseed (Gossypium hirsutum L. ‘Atlas 67′) oil quality was measured by gas-liquid chromatography. Postemergent applications of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) (0.22, 0.34, or 0.45 kg/ha); 1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea (fluometuron) (0.56, 1.12, or 1.68 kg/ha); or 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne) (0.22, 0.45, or 0.90 kg/ha) in phytobland oil (4.7, 9.3, or 14.0 L/ha) did not modify the percentage myristic, palmitic, palmitoleic, stearic, oleic, linoleic, linolenic, or arachidic acids when compared to cotton treated with phytobland oil alone or the three herbicides without oil.

The phytotoxicities of four substituted dinitroanilines, N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine (benefin), 2,6-dinitro-N,N-dipropylcumidine (isopropalin), 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin), and α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), to eggplant (Solarium melongena L. ‘Black Beauty’), pepper (Capsicum annuum L. ‘Vindale’), and tomato (Lycopersicon esculentum Mill. ‘VF 145-B-7879′) were studied. Nitralin and trifluralin were most active in inhibiting root elongation and top growth of these plants, the effect of benefin was intermediate, and isopropalin was the least active herbicide. The order of crop tolerance was as follows: tomato > pepper > eggplant. The effect of these herbicides on two pathogenic fungi, Rhizoctonia solani Kuehn and Fusarium oxysporum f. sp. lycopersici (Sacc.) Snyd. and Hans. was tested in culture and was found to be quantitatively and qualitatively different from that on plants. With both fungi benefin and trifluralin were more toxic than isopropalin, while nitralin showed a very low toxicity. R. solani was the less sensitive fungus.

Early spring spray applications of the potassium salt of 4-amino-3,5,6-trichloropicolinic acid (picloram) and certain formulations of 1:1 mixtures of picloram plus (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) controlled yaupon (Ilex vomitoria Ait.). Ester formulations of picloram or picloram plus 2,4,5-T were ineffective. Combinations of surfactant and oil: water carriers usually did not improve herbicide performance over water carriers. Granular picloram was superior to sprays when applied as soil treatments at equal rates and controlled yaupon at most dates of application. Post oak (Quercus stellata Wangenh.) and blackjack oak (Quercus marilandica Muenchh.) were controlled more effectively by picloram or picloram plus 2,4,5-T sprays on the foliage than by granular picloram as a soil treatment. Picloram granules usually killed winged elm (Ulmus alata Michx.) regardless of date of application.

We investigated the forces involved in the adsorption and desorption of 4-amino-3,5-6-trichloropicolinic acid (picloram), 1,1-dimethyl-4,4′-bipyridinium ion (paraquat), and α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) using cationic, anionic, and nonionic exchange resins. The anionic resin (Cl-form) adsorbed 375, 0.08, and 0.67 mg of picloram, paraquat, and trifluralin, respectively, per gram of oven-dry resin. The nonionic resin adsorbed 4.0, 0.34, and 10.0 mg of picloram, paraquat, and trifluralin, respectively, per gram of oven-dry resin, while the cationic resin (H-form) adsorbed 2.3, 226, and 0.17 mg of picloram, paraquat, and trifluralin, respectively. Other cationic resins (Na-form and Ca-form) performed similarly to the hydrogen form. Desorption studies indicated that picloram was adsorbed mainly in the anionic form by coulombic forces (electrostatic) and to a lesser degree by weak physical bonding (van der Waal's forces). Paraquat was adsorbed as a cation through coulombic forces. Trifluralin was mainly absorbed by physical bonds at sites on the resins where there were no coulombic forces.

Rapid absorption and acropetal translocation of 14C from p-nitrophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether (fluorodifen) labeled with 14C at either the 1 position of the p-nitrophenyl ring (fluorodifen-1′-14C) or the trifluoromethyl carbon (fluorodifen-14CF3) were observed in cucumber (Cucumis sativus L. ‘Ashley’) seedlings after root treatment via nutrient solution. The major degradative products of fluorodifen-1′-14C were p-nitrophenol and Unknown I (possibly a conjugate of p-nitrophenol). Some p-nitrophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether (2-amino-fluorodifen), p-aminophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether (p,2-diamino-fluorodifen), p-aminophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether (p-amino-fluorodifen), and several minor unknowns also were detected. The major degradative product of fluorodifen−14CF3 was Unknown II (possibly a conjugate of 2-amino-4-trifluoromethylphenol). Also detected were some 2-amino-fluorodifen, 2-amino-4-trifluoromethylphenol, p-amino-fluorodifen, p2-diamino-fluorodifen, 2-nitro-4-trifluoromethylphenol, and several minor unknowns. The basic difference in susceptibility to fluorodifen of cucumber and peanut (Arachis hypogaea L. ‘Starr’) appears to be due to the rate of acropetal translocation (cucumber translocates more than peanut) and the rate of degradation (peanut degrades fluorodifen much more rapidly than cucumber).

The control of grasses and broadleaf weeds in sunflowers (Helianthus annuus L. ‘Peredovik’) generally was as good with one or two cultivations during the 3-year period as with chemicals applied alone or in sequence with cultivation. Plant injury was not evident from mechanical treatments or from α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). However, plant injury occurred when plots were treated with 2-chloro-2′6-diethyl-N-(methoxymethyl) acetanilide (alachlor) plus 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne) as a preemergence application in 1 year and from postemergence applications of 2-tertiobutyl-4-(2,4-dichloro-5-isopropyloxyphenyl)-5-oxo-1,3,4-oxodiazoline (RP 17623) and 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) in 2 years. Seed yields from plots cultivated once were as good as yields from plots that received multiple cultivation or herbicide treatments. Other agronomic characteristics were favorable from plots that received one cultivation.

Herbicide content in honey mesquite (Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell) phloem 48 hr after treatment was higher in stems within 20 cm of the foliage than in those near the soil line. Similar levels of (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) occurred from applications of either 0.56 or 1.12 kg/ha, whereas three times as much 4-amino-3,5,6-trichloropicolinic acid (picloram) occurred in plants sprayed with the high rate than in those sprayed with the low rate. Herbicide concentration was highest in June and lowest in August.

The compound α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) inhibited mitosis in onion (Allium cepa L. ‘Yellow Globe’) and wheat (Triticum aestivum L. Thorn’) root tips. Photomicrographs showed that trifluralin affected mitosis in the same manner as colchicine. Arrested metaphases, c-pairs, micronuclei, amoeboid nuclei, and polyploidy were observed at various times after treatment. An increase in the percentage of arrested metaphases and a decrease in anaphase and telophase figures after 3 hr showed that mitosis was being blocked at metaphase. Prophase did not appear to be affected. Centrifugation of treated root tips displaced the chromosomes of arrested metaphases indicating that the spindle apparatus was disrupted.

Tillering, flowering, and rhizome formation of johnsongrass (Sorghum halepense (L.) Pers.) started approximately 2 months after planting seeds or single-node rhizome fragments in the warm season. The minimum temperature for rhizome formation was between 15 and 20 C. Inflorescences were produced only from May to November. No causal relationship was found between flowering and rhizome formation. The bud activity of new rhizomes, as assessed by sprouting of single-node fragments, ranged between 48 and 100%. Sprouting was nil at 10 C, slow below 20 C, and maximum at 28 C. Seed germination required a temperature about 10 C higher than rhizome sprouting. While the initial leaf production of seedlings was more rapid than on plants produced from rhizomes, other differences in growth and development between seedlings and rhizome plants were of only limited practical significance.

Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine (ametryne) were tested for growth regulatorlike effects. In the presence of 10 μg/ml of kinetin, atrazine had no effect on the growth of callus tissue of soybean (Glycine max Merr. ‘Lee’), but ametryne at 10−14M concentration stimulated callus growth and the production of roots. High concentrations of both atrazine and ametryne inhibited the growth of excised roots of tomato (Lycopersicon esculentum Miller ‘Atkinson’). Ametryne, and to a lesser extent atrazine, increased percent germination of seed of lettuce (Lactuca sativa L. ‘Grand Rapids’) and tobacco (Nicotiana tobaccum L. ‘Sansum’) exposed to only 4 min of red light. Both atrazine and ametryne stimulated adventitious root formation by excised hypocotyls of mung beans (Phaseolus aureus Roxb.) in the absence of 10 ppm of exogenous indoleacetic acid (IAA) but not in its presence. A high concentration of atrazine (10−6M) in the presence of IAA decreased root initiation in comparison with the IAA-treated controls.