PLANT GROWTH STIMULATION BY SUBLETHAL CONCENTRATIONS OF HERBICIDES*

Summary. Significant stimulation of root or shoot growth of oats (Avena sativa L.) resulted from pre-emergence applications of eleven herbicides at sublethal doses. Two additional herbicides stimulated cucumber (Cucumis sativus L.) root growth. Several types of herbicides with different mechanisms of lethal action were represented. Three herbicides failed to stimulate plant growth significantly in these studies, although all of them have been observed to cause growth stimulation in other experiments. Studies on oat seedling respiration, photosynthesis, protein content, free amino acid content, and total available soluble carbohydrates failed to provide any consistent explanation for stimulation. These results provide further evidence of the validity of the Arndt-Schulz hypothesis which states that all poisons are stimulatory at sublethal concentrations. Stimulation de la croissance des plantes par des concentrations sublétales d'herbiddes Résumé. Une stimulation significative de la croissance des racines ou des tiges de I'avoine (Avena sativa L.) a été provoquée par l'application en pré-levée de onze herbicides à des doses sublétaies. Deux autres herbicides ont stimulé la croissance des racines de concombre. Plusieurs types d'herbicides possédant des mécanismes diffrénts d'action létale étaient représentés. Trois herbicides n'ont pas provoqué de stimulation significative de la croissance au cours de cette étude, bien qu'ils aient provoqué une stimulation dans d'autres expériences. Des recherches sur la respiration, la photosynthése, la teneur en protéines, en amino-acides libres et le total disponible des hydrates de carbone solubles dans la plantule d'avoine n'ont fourni aucune explication logique de la stimulation. Ces résultats apportent une nouvelle preuve de la validité de l'hypothése d'Arndt-Schulz selon laquelle tous les poisons ont un effet stimulant à des concentrations sublétaies. Förderung des Pflanzenwachstums durch Herbizide in sublethalen Konzentrationen Zusammenfassung. Die Vorauflaufanwendung von elf Herbiziden in sublethalen Dosen förderte das Wurzel- und Sprosswachstum von Hafer (Avena sativa L.) signifikant. Zwei weitere Herbizide stimulierten das Wurzelwachstum bei der Gurke (Cucumis sativus L.). Es waren Herbizide aus verschiedenen Gruppen mit unterschiedlichem Mechanismus der lethalen Wirkung vertreten. Drei Herbizide förderten in diesen Studien das Wachstum nicht signifikant, obwohl eine solche fördernde Wirkung in anderen Experimenten beobachtet worden war. Untersuchungen der Atmung von Haferkeimlingen, der Photosynthese, des Proteingehaltes, des Gehaltes an freien Aminosäuren und der Gesamtmenge an löslichen Kohlenhydraten erbrachten keine einheitliche Erklärung für die Förderung. Diese Ergebnisse stützen die Gültigkeit der Arndt-Schulz Hypothese, die besagt, dass alle Gifte in sublethalen Dosen stimulierend wirken.     

RATE OF DETOXIFICATION OF 4-AMINO-3,5,6-TRICHLOROPICOLINIC ACID IN SOIL

Summary. 4-Aniino-3,5,6-trichloropicolinic acid was incubated at 70° F in thirteen different soils for periods of up to 2 years at a concentration range of 0–023–24 ppm. Losses varied from complete to non-measurable by the bioassay technique employed. The percentage decomposed was generally greater for lower initial concentrations. The results were mathematically analysed in terms of zero-order, half-order, first-order and Michaclis-Menten kinetics. Half-order and Mirhaelis-Menten were found to be the kinetic expressions that most satisfactorily described the detoxification of the herbicide in soil.
Taux de deloxification de l'acide 4-amino-3,5,6-trichloropicolinique dans le sol     

THE TOXICITY OF PARAQUAT TO A RANGE OF SPECIES FOLLOWING UPTAKE BY THE ROOTS*

Summary. The sensitivity of eight species to paraquat taken up through the roots was tested in nutrient solution experiments. Ryegrass, lettuce and carrot, which were found to be the most sensitive, were assessed for response to paraquat in a peat soil. Lettuce and ryegrass were the most suitable of the eight species for soil bioassays. Toxicité du paraquat pour diverses espéces aprés absorption par les racines Résumé. La sensibilité de huit espéces au paraquat absorbé par les racines a étéétudiée dans des experiences en solutions nutritives. Le ray-grass, la laitue et la carotte qui se sont montrés les plus sensibles furent employés pour évaluer la réaction au paraquat dans un sol tourbeux. La laitue et le ray-grass furent, parmi les huit espéces, les plus appropriate aux essais biologiques. Phytotoxizitdt von Paraquat gegeniiber einer Anzahl von Arten nach Wurzelaufnahme Zusammenfassung. Die Empfindlichkeit von acht Arten gegenuber Paraquat nach Wurzel Aufnahme wurde in Wasserkulturversuchen untersucht. Weidelgras, Salat und Möhren hat ten sich als am empfindlichsten erwiesen und wurden auf ihre Reaktion gegenuber Paraquat in einem Lehmboden untersucht. Salat und Weidelgras erwiesen sich von den acht untersuchten Arten als die beiden geeigneuten für Bodenbiotests.     

THE ADSORPTION OF FOUR HERBICIDES BY DIFFERENT TYPES OF ORGANIC MATTER AND A BENTONITE CLAY*

Summary. A bioassay was used to study, adsorption of prometryne, simazine, linuron and pyrazon by fibrous peat, sphagnum moss, muck soil and bentonite as 1 % mixtures with quartz sand. Of these bentonite caused least reduction in bioactivity, and sphagnum moss reduced it only slightly more. Fibrous peat and muck soil were the most adsorptive. Prometryne, simazine and pyrazon were more highly adsorbed by fibrous peat than by muck soil, while for linuron the opposite occurred. Fibrous peat was approximately three, seven, thirteen and three times more adsorptive than bentonite for pyrazon, linuron, prometryne and simazine, respectively, while for muck soil the corresponding values were two, fourteen, seven and two. Studies with prometryne and five different soils indicated that percentage organic matter, cation-exchange capacity and specific surface area were all highly correlated with adsorption.     

棉铃虫Bt抗感种群间数种解毒酶和中肠蛋白酶活性的比较

比较Bt抗性种群和敏感种群棉铃虫解毒酶和中肠蛋白酶的变化，测定两种群的α-乙酸萘酯酶、乙酰胆碱酯酶、谷胱甘肽-S-转移酶的酶活力，比较α-乙酸萘酯酶和乙酰胆碱酯酶的Km和Vmax值，并采用特异性酶抑制剂进行鉴定，结果发现，抗性种群棉铃虫的乙酰胆碱酯酶活力、Km和Vmax值都 显著升高，甲基对氧磷对抗性种群棉铃虫乙酰胆碱酯酶的抑制程度比敏感种群明显霸产加，抗生种群5和敏感种群总蛋白酶活力差异不显著，弱碱性类胰蛋白酶和类凝乳蛋白酶活力差异也不显著，但抗性种群3龄幼虫的强碱性类胰蛋白酶活图形显著高于敏感种群。     

RESPONSE OF YELLOW NUTSEDGE,FLORIDA PUSLEY,AND PEANUTS TO THIOCARBAMATE HERBICIDES AS AFFECTED BY METHOD OF PLACEMENT IN SOIL*

Summary. Thiocarbamate herbicides were applied with incorporation devices and new subsurface application equipment on loamy sand at Tifton, Georgia, U.S.A. Subsurface-applied ethyl N,N-dipropylthiolcarbamate (EPTC), S-propyl bulylethylthiocarbamate (pebulate), and S-propyl dipropylthiocarbamate (vernolate) generally gave better control of Cyperus esculentus L. and Richardia scabra St Hil, but injured peanuts more than applications made on the soil surface and then incorporated into the soil. For soil incorporation, the power-driven rotary hoe was generally better than a disc harrow. Depth of subsurface placement critically affected herbicidal activity, especially on Cyperus esculentus; placement 1·5 in. below the soil surface gave more effective control than placement at 5·5 in. Réactions de Cyperus esculentus, de Richardia scabra et de l'arachide mix herbicides à base de thiocarbamate, en relation avec la methode de placement dans le sol     

SITE OF UPTAKE OF SOIL-APPLIED HERBICIDES*

Summary. We conducted studies to determine the effects on corn (Zea mays L, var. Indiana 654) and pea (Pisum sativum L. var. Alaska) of localizing various herbicides in the soil, using a double plastic pot technique which ensured separate exposure of the root and shoot zones of the plants to treated soil. Effects on corn and pea were similar in relation to site of uptake. 2,4-D-amine, naptalam, simazine, diuron and dalapon-sodium entered primarily through the roots. Some shoot entry and also severe inhibition of roots occurred in soil treated with 2,4-D and naptalam; these were noticed only to a slight extent with the other three herbicides. EPTC, chlorpropham and trifluraiin were most effective when applied to the shoot zone. Little effect on foliage growth was evident when the root zone alone was treated. However, roots in treated soil were severely inhibited by these three herbicides. Dinoseb displayed a contact type of action, injuring both shoots and roots. Treatment of both zones had an additive effect. Entry of chlorthal-methyl which was tested on a susceptible species, sorghum (Sorghum vulgare Pers.) was mainly through the shoot, with only a slight effect on top growth when roots alone were treated. Roots in treated soil were slightly inhibited. Localisation de l'absorption des herbicides appliqués sur le sol     

UPTAKE OF COPPER IN HYDRILLA*

Summary. A linear increase from 933 to 15,943 ppmw of copper occurred in hydrilla (Hydrilla verticillata Casp.) 4 days after treatment with copper sulphate pentahydrate (CUSO₄. 5H₂O, CSP) at 0·5–4·0 ppmw of copper. Neither increase in calcium levels to 0·8 MM in the ambient solution nor aeration affected the amount of copper in excised hydrilla tissue during a 24-h treatment period with CSP at 1·0 ppmw of copper. Part of the accumulated copper appeared to be bound in hydrilla. A higher accumulation of copper occurred after treatment with an organic copper complex (cutrine) than with either CSP or copper chloride (CuCI₂.2H₂O, at 1·0 ppmw of copper. This high accumulation with cutrine appeared to be related principally to the amount of copper remaining in the treatment solution.     

FACTORS AFFECTING THE PHYTOTOXICITY OF PARAQUAT*

Summary. Temperatures of 5–6° C delayed leaf necrosis of glasshouse-grown oats (Avena sativa), winter peas (Pisum sativum), huisache (Acacia farnesiana), mesquite (Prosopis julijiora var. glandutosa), live oak (Quercus virginiana) and yaupon (Ilex vomitoria) for at least 48 hr after treatment with paraquat as compared with higher temperatures. After 96 hr, oats, winter peas, huisache and mesquite at 5° C usually showed as much necrosis as plants at 24–28° C. Similar results were obtained with live oak and yaupon, and with yaupon in the field, except that longer periods were sometimes required for plants at low temperatures to develop injury comparable with that at higher temperatures. Washing yaupon and live oak leaves 1 hr after application reduced the effectiveness of paraquat regardless of temperature, but washing winter peas 10 min after application had little or no effect on phytotoxicity. Field-grown mesquite showed extensive leaf necrosis when leaves were washed after 20 min, live oak leaves similarly treated and washed were not injured, while the response of winged elm (Ulmus alata) was intermediate. Percentage leaf necrosis of mesquite, winged elm, yaupon and live oak increased with increasing paraquat concentration; 6–9 μg/leaf on mesquite and 20 μg/leaf on winged elm gave 100% necrosis after 4 days. Complete leaf necrosis of live oak and yaupon was not attained during this period even with 80 μg/Ieaf. Nursery-grown mesquite, yaupon and greenbriar (Smilax bona-nox) and natural stands of yaupon were treated at two growth stages, in March and May. Paraquat was more effective on mesquite when applied in May, but there were no differences with the other species. Facteurs affectant la toxicité du paraquat     

EVALUATION OF HERBICIDE PERSISTENCE IN SOIL*

Summary. The persistence of ten herbicides in soil was tested in the glasshouse over a 5–month period, using an oat bioassay. Simazine and diuron were highly persistent, atrazine persistent, fluometuron, trifluralin, bromacil and noruron moderately persistent, and pyrazon, prometryne and ametryne of short persistence. Six of these herbicides were also included in a field experiment consisting of logarithmically sprayed strips on which oats were sown at ten intervals of 1 month; changes of herbicidal activity with time were evaluated by measuring the length of the strip showing herbicidal injury. Results corroborate those of the glasshouse experiments except for trifluralin which was more persistent in the field. Disappearance curves were generally sigmoidal. The more persistent compounds showed a long period of slow disappearance followed by rapid disappearance.     

SHOOT ZONE UPTAKE OF SOIL-APPLIED HERBICIDES*

Summary. Studies were conducted to determine the effects of herbicide placement at different zones of maize (Zea mays L.) and pea (Pisum sativwm L.) shoots below the soil surface after emergence. Soil was removed from around the shoots and replaced with herbicide-treated soil. A wax barrier ensured separate exposure of the zones to treated soil. EPTC, chlorpropham, propham and sulfallate did not affect pea shoot growth, but in maize the shoot zone adjacent to the crown root node was extremely sensitive. Treatment in this area markedly reduced growth and severely inhibited the crown roots. The difference in susceptibility between these species may he due to the location of the growing point relative to the treated soil. Shoots of maize and pea were sensitive to diuron. In maize the shoot adjacent to the crown root node and the tissue of the first internode were the most susceptible. In pea the- uppermost shoot (beneath the soil surface) was the most sensitive. Trifluralin did not affect growth of maize and pea when placed in the shoot zone after emergence, although the crown roots of maize were severely inhibited. Naptalam, dalapon and 2,4-D did not affect growth of maize under similar conditions, and of these only 2,4-D reduced growth of pea. Zone d'abiorption des tiges pour les herbicides appliqués sur h sol     

蛋清蛋白和伴清蛋白激发荧光在鉴别细菌中的作用

 近年来,各类选择性或鉴别性培养基发展很快,因为它不仅在分离、鉴定、诊断上提供了简单方法,而且用于生态、流行、侵染的研究,大大增加了我们对病原细菌在自然界生活的了解。     

CHEMICAL INHIBITION OF CROP GERMINATION BY WEED SEEDS AND THE NATURE OF INHIBITION BY ABUTILON THEOPHRASTI

Summary. Aqueous extracts of the ground seeds of thirteen weed species were assayed for their ability to inhibit the germination on filler paper of eight crop species. All of the extracts delayed germination of at least some of the crop species. Germination of some crop species was delayed when the crop seeds were surrounded by weed seeds on filter paper, The seeds of Abutilon theophrasti were inhibitory to tomato ( Lycopersicum esculentum ) germinated in sterile and non-sterile soil in the laboratory. The inhibition of germination was apparent under conditions which excluded light, water and minerals as factors in the competition. Chemical studies indicated that the inhibition by Abutilon seeds was due to free amino acids emanating from the seeds.
Inhibition chimique de la germination de plantes cultivées par des semences de mauvaises herbes et nature de l'inhibition par Abutilon theophrasti     

DEGRADATION OF BROMOXYNIL IN REGINA HEAVY CLAY*

A spectrophotometric method was developed to detect bromoxynil in Regina heavy clay, and the breakdown under different temperature and moisture conditions was studied. At rates equivalent to 14 kg/ha, over 50% of the applied bromoxynil was degraded in 2 weeks at 25°C and at moisture levels in excess of the wilting point. Losses at 18°C were slightly slower. Little breakdown occurred in sterile soil, indicating that microbial degradation could be an important factor contributing to bromoxynil breakdown under field conditions. Paper and thin-layer chromatographic techniques were used to isolate and identify soil degradation products. In addition to the parent compound small amounts of 3,5-dibromo-4-hydroxybenzamide and 3,5-dibromo-4-hydroxybenzoic acid were detected.