The effect of 1,4-naphthoquinone, 1,4-benzoquinone, and several CI and NH2-substituted quinones has been studied on growth, chlorophyll concentration, and oxygen evolution in Chlorella pyrenoidosa Chick. (Emerson strain). Drastic decrease of the studied parameters usually was noted after 24 to 48 hr treatment at 3×10–5 M concentration. The effect of the quinones was compared with that of 6,7-dihydrodipyrido [l,2-a:2,l-c-]pyrazidinium salt (diquat) and 3-(3,4-dichlorophenyl)-l,l-dimethylurea (diuron). Diuron inhibited oxygen evolution immediately after addition, but could be washed out and the effect was reversible. Diquat had no inhibitory effect on oxygen evolution and chlorophyll content but caused a slight decrease in cell number. Although some quinones have an almost immediate effect on the oxygen-evolving mechanism, it seems more likely that the overall effect of the quinones is on the total physiological activity of the algal cells. Oxygen evolution seems to affected earlier than chlorophyll destruction, and the observed long-term damage is irreversible. Most of the compounds studied could be classified as algicidal, with the exception of diuron, diquat, and 1,4-benzoquinone which may be considered to be algistatic.

Combinations of 3-(3,4-dichlorophenyl)-l,l-dimethylurea (diuron) with O,O-diethyl S-2-(ethylthio)-ethyl phosphorodithioate (disulfoton) or O,O-diethyl S-(ethylthiomethyl) phosphorodithioate (phorate) in soil resulted in synergistic phytotoxicities. These synergistic phytotoxicities persisted 21 to 27 weeks in alternately fallow-cropped soils treated with 0 to 12 ppm disulfoton or phorate and 0 to 1.0 ppm diuron where oats (Avena sativa L., var. Mark-ton) was the bioassay plant, and persisted 5 to 15 weeks in alternately fallow-cropped soils treated with 0 to 12 ppm disulfoton or phorate and 0 to 1.33 ppm diuron where corn (Zea mays L., var. US 13) was the bioassay plant. The persistence of the combined pesticides corresponded closely with persistence of the individual pesticides. Corn and cotton (Gossypium hirsutum L., var. Acala 4-42) were more tolerant than was oats to diuron and diuron-insecticide combinations.

The depths of leaching of S-ethyl dipropylthiocarbamate (EPTC), S-propyl butylethylthiocarbamate (pebulate), S-propyl dipropylthiocarbamate (vernolate), S-ethyl hexahydro-lH-azepine-l-carbothioate (molinate), and S-ethyl cyclohexylethylthiocarbamate (hereinafter referred to as R-2063) were compared in five different types of soils contained in glass columns. The depths of leaching in mineral soils were directly correlated with the water solubilities of the herbicides. The order of leaching from greatest to the least was molinate, EPTC, vernolate, pebulate, and R-2063. With all compounds tested, the depth of leaching decreased as the clay content of the soil increased. Leaching depth also decreased as organic matter increased. In peat soil containing 35% organic matter, no movement out of the treated zone could be detected with any of the thiocarbamate herbicides tested when leached with 8 in of water.

Quackgrass (Agropyron repens (L.) Beauv.) was defoliated for 25 to 30 days with applications of 1.0 lb/A of l,l′-dimethyl-4–4′-bipyridinium salt (paraquat). Applications were more effective made prior to darkness than at midday. Phytotoxicity was increased by adding surfactants in the field, and experiments utilizing 14C-paraquat under controlled environmental conditions indicated that the surfactant X-77 increased foliar absorption by 20%. Quackgrass plants grown in nutrient solutions exhibited chronic paraquat toxicity which increased as the nitrogen levels increased. Paraquat also inhibited the growth of lateral buds on quackgrass rhizome segments cultured in the dark. Greater movement of 14C-paraquat in quackgrass leaves occurred under 6 hr of light as compared to 6 hr of darkness following application. However, a 6-hr dark period after application prior to the light period further enhanced the movement from the treated leaf.

Oxygen uptake and oxidative phosphorylation were inhibited by 10–4 M of α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) in isolated mitochondria of corn (Zea mays L., var. Dixie 18), Sorghum (Sorghum vulgare Pers., var. Early Hegari) and Soybean (Glycine max L., var. Lee). Little or no inhibition was detectable at 10–5 and 10–6 M in corn and sorghum. Data for 4-(methylsulfonyl)2,6-dinitro-N,N-dipropylaniline (nitralin) were more variable but similar. The effects on these processes do not seem to be related to the selectivity of trifluralin since it caused a greater reduction in oxygen and phosphate uptake in resistant species (soybean) than the susceptible species (sorghum).

Herbicide tests conducted over a period of 3 years indicated that 3-(3,4-dichlorophenyl)-l,l-dimethylurea (diuron) at 2.5 lb/A preemergence, or a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) at 2.0 lb/A preemergence, incorporated, are safe and effective herbicides for weed control in gladiolus (Gladiolus grandiflorus). Applications of dimethylamine salt of 2,4-dichlorophenoxyacetic acid (2,4-D) applied as directed sprays at rates of 0.5 to 1.0 lb/A prior to spiking controlled late season weeds without apparent injury to the plants.

The uptake and transport of carboxyl-labeled and unlabeled butoxyethyl esters and ammonium salts of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) by honey mesquite (Prosopis juliflora (Swartz) DC, var. glandulosa (Torr.) Cockerell) leaves were compared as measured by liquid scintillation counting and gas chromatography. Absorption of 2,4,5-T was determined by assaying leaf-rinsing solutions and extracts of treated leaves. Transport of 2,4,5-T was measured by determining amounts of 2,4,5-T found in stem tissue. The methods of analysis gave comparable results when extraction, cleanup, and analytical procedures were identical. When cleanup and methylation procedures were eliminated for the radioisotopic analyses, radioisotopic analyses gave significantly higher values for extracts of treated leaves than did gas chromatographic analyses. Larger amounts of 2,4,5-T were recovered from leaves treated with the butoxyethyl esters of 2,4,5-T than with ammonium salts.

Requirements for germination of 23 medusahead (Taeniatherum asperum (Sim.) Nevski) selections were investigated in relation to temperature and afterripening requirements, and were compared with the germination characteristics of other grasses. Medusahead germinated best at 10 to 15 C. Germination percentages were markedly lower at 20 and 25 C. Unlike medusahead, germination of all competing or replacement species tested was markedly decreased at lower temperatures (10 C). Above 15 C, medusahead selections had strong afterripening requirements which decreased over time. Shortly after maturity, medusahead caryopses germinated only at low temperatures (10 and 15 C). Germination temperatures became less dominant after a 180-day afterripening period.

The hypothesis that plants treated with 2,4-dichlorophenoxyacetic acid (2,4-D) die as a consequence of abnormal growth has been examined. Cocklebur (Xanthium sp) plants spot treated on one leaf with 2,4-D show three phases of growth toward death. For the first 2 days after treatment, there is a net weight increase, largely due to abnormal growth of the axis (apex, stem, and tap root). Root and leaf growth are drastically curtailed. Between 2 and 7 days, axis growth continues primarily at the expense of leaf tissue which is induced to senesce, especially the cotyledons. The last phase between 7 and 10 days leads to collapse and withering of plants, and was not examined in detail.

Analyses for nitrogenous constituents show the usual mobilization to the axis, with early and large increases in nucleic acid. Both photosynthesis and ion absorption are initially stimulated but decline sharply after the first day. Translocation to leaves and roots is drastically reduced in favor of the proliferating axis.

The death of the plant appears to be due to suppression of normal apical growth coupled with induction of abnormal axis growth. Failure to produce new root and leaf tissue plus inadequate nutritional maintenance of existing roots and leaves lead to lack of autotrophism and eventual death. The biochemical basis for these responses appears to be with aberrant nucleic acid metabolism.

Laboratory experiments and field observations were made to study reproduction and overwintering of cabomba (Cabomba caroliniana Gray) in New Jersey. Flowering begins in late June and continues until frost. Overwintering is accomplished chiefly by means of vegetative portions of the plant. No evidence of reproduction by seed was found in the field. No seeds germinated in the laboratory under any of the environmental conditions imposed on them. Microscopic sections of seeds were prepared and examined; no embryos were present in these sections.

A survey of the phytophagous insect fauna of Russian thistle (Salsola kali L., var. tenuifolia Tausch) showed that this weed serves as an alternate feeding and/or breeding host to a number of economically important insects in southern California.

Rates of 0 and 5 lb/A of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) or 2-chloro-4,6-bis(ethylamino)–s-triazine (simazine) were combined with O and 200 lb/A of nitrogen fertilizer as preemergence applications on plots planted to corn (Zea mays L., var. Mo. 880) in May of 1964 and 1965. Soil samples collected in December, 1965, and again in February, 1966, were plated on Difco potato dextrose agar and nutrient agar to determine the growth of fungal and bacterial colonies. There was no difference in the total number of fungal colonies grown on media seeded with soils from the field studies, yet variation in individual species occurred. The number of bacterial colonies increased on plates seeded with soil from plots treated with 200 lb/A of nitrogen plus 5 lb/A of simazine but not from simazine-treated soil without nitrogen.