One of the most marked effects of herbicidal concentrations of 2,4-D (2,4-dichlorophenoxyacetic acid) is the swelling and proliferation of basal stem tissues. Sell et al. reported a large increase in the protein content of stems of bean plants treated with 2,4-D. Shaw, et al. observed an increase of total protein in plants treated with 2,4-D and Rebstock, et al. found the nucleic acid content to double in the stems of bean plants treated with 2,4-D. Rebstock et al. postulated that nucleic acid was involved in the unusual growth and development of the plant. Skoog has presented an attractive hypothesis linking auxin action with nucleic acid metabolism. Current biochemical investigations leave little doubt that RNA (ribonucleic acid), particularly of the microsome fraction of the cytoplasm, is involved in protein synthesis. Furthermore, RNA appears to be implicated in oxidative phosphorylation and ion absorption, two processes known to be affected by 2,4-D.

As reported in the previous paper, 2,4-D (2,4-dichlorophenoxyacetic acid) caused marked changes in the RNA (ribonucleic acid) content of seedling stem tissue, particularly in the microsome fraction. The ribonucleoprotein particles of the microsome fraction participate in protein synthesis and any abnormality in their metabolism could conceivably result in biochemical and physiological disorders leading to the death of the plant.

The small size and slow growth of legume seedlings make them susceptible to damage or elimination by weed competition. Various methods of establishment such as sowing in late summer, sowing with a small grain companion crop, or mowing have not been entirely successful. The increased use of weed-controlling chemicals has awakened considerable interest in the establishment of legumes with the aid of herbicides. Research workers are in agreement that 4-(2,4-DB) [4-(2,4-dichlorophenoxy)butyric acid] can be safely used to control broad-leaved weeds in legumes. However, there is some difference of opinion as to the rates of various formulations that can be safely used.

The use of herbicides for controlling weeds in the grape row is becoming resolved in mature vineyards. Oil and DNBP mixtures can be used because of the protective covering of old bark on the trunk. Herbicides such as CIPC, monuron and diuron can be used as a band treatment in the row because of the resistance to these chemicals where only a portion of the root zone is treated. Most of the above references caution about the use of these materials on young vineyards or transplants.

The use of various arsenic compounds as herbicides to control undesirable vegetation, reducing fire hazards and allowing convenient access, has long been recommended.

One of the important areas of current herbicide research is the investigation of herbicide mixtures. It is a common field experience that use of a single material—even of a “broad-spectrum” herbicide—exerts a selective pressure on the field population because of differential effectiveness on the various weed species. There is some evidence that a part of this derives from purely mechanical considerations (e.g., the spraying system in use may not reach plants of different growth habit equally well), but in any case the weed control program often appears to decrease in effectiveness after several seasons. In addition to favoring the survival of particular species, the non-eradicatory application of even a highly efficient chemical apparently aids in the establishment of populations of individuals which are physiologically most tolerant of the herbicide used. It will probably be granted, then, that the use of mixtures of toxicants will provide more effective control of populations of mixed weed species, and may also reduce the numbers of individuals and species exceptionally tolerant of the herbicide program, especially when the toxicants kill by affecting different physiological processes.

The present experiments were part of a study to determine the mechanisms by which herbicides affect plant growth and to find metabolites which protect growth against the inhibitory actions of herbicides. Bakers' yeast was selected for use in preliminary investigations because its rapid growth rate facilitates examination of large numbers of herbicide-metabolite combinations. The experiments reported herein present evidence which implicates histidine metabolism as a growth process which is sensitive to 3-amino-1,2,4-triazole [amitrole].

Investigations during the past three decades have confirmed that field bindweed (Convolvulus arvensis) is exceedingly difficult to eradicate. Since the introduction of sodium chlorate by Latshaw and Zahnley various other soil sterilants have been used successfully for spot treatments. Timmons reported the effect of various systems of intensive cultivation on bindweed control as influenced by root reserves. Phillips and Timmons reported the response of bindweed to crop competition and combinations of cropping, cultivation and 2,4-D. The introduction of 2,4-D (2,4-dichlorophenoxyacetic acid) provided a new tool for bindweed control and an impetus for continued research.

Rhizome initiation and growth is a contributing factor to the problem of controlling Johnsongrass (Sorgum halepense (L.), Pers.). Control methods by intensive cultivation or chemical applications are directed primarily toward the destruction of these underground structures. As described by Fletchall et al. rhizomes are fleshy, segmented underground stems having scales at the nodes. Their development is rapid; they function as organs for carbohydrate storage, and as reproductive structures which produce vegetative shoots from axillary and terminal buds. Information relative to development of rhizomes and their response to various treatments is reported; this is essential to understanding and evaluating methods of control.

This report describes the preparation, purification, and properties of 18 new herbicides, amino acid derivatives of 2,2-dichloropropionic acid (dalapon) and 2,3,6-trichlorobenzoic acid (2,3,6-TBA). The biological evaluation of the compounds as selective herbicides is being made by other investigators and will be published later. Some of the compounds are also being evaluated for nematocidal, fungicidal, and anticancer properties.

Several investigators have now reported that phenylurea herbicides inhibit the photochemical activity (Hill reaction) of isolated chloroplasts. Many of the phytotoxic symptoms in plants treated with phenylurea herbicides can be explained on the basis that the herbicides have blocked the photosynthetic mechanism. This action has been suggested as the primary cause of toxicity under field conditions. The metabolic product of biochemical pathways containing the primary site of action of a herbicide can be applied to barley plants in sufficient quantity to eliminate completely some of the toxic symptoms produced by the herbicide. Geoghegan has reported that glucose applications caused an increase in the concentration required for three phenylurea compounds to inhibit growth of Chlorella vulgaris. Therefore, a determination of the effect of carbohydrates on the inhibition of growth of barley seedlings in the presence of several phenylurea herbicides seemed of interest.

The possibility of using 2,4-D as a soil sterilant was investigated by Crafts in 1949. He concluded that 2,4-D may be useful under very dry conditions. In 1954, Shafer reported several years work using soil applications of 2,4-D for control of perennial weeds. Since that time many research workers have evaluated 2,4-D and other phenoxy herbicides for the control of bindweed and other perennial weeds. Results of these trials varied from excellent to poor.

In order to protect young apple trees, in the years immediately following planting, from competition for moisture and plant food it is a generally accepted practice to keep the area around the trees free of weeds. The traditional method of doing this has been to clean cultivate, the area next to the trees being kept clean by hand labour.

The technique used in the tests herein reported is based on the inhibition of root elongation by growth substances, an exceedingly sensitive response. Two procedures are used in the application of the growth substances. The first consists of applying known amounts of test compounds to the root bathing solution of mesquite seedlings, and the second procedure consists of applying these compounds to the cotyledons. After addition of the growth regulator to the solution subsequent root inhibition is dependent on absorption by the root tissue and accumulation in an active form at the site of action. In cotyledonary applications, translocation as well as absorption is necessary before inhibition of root elongation will occur. It was the objective of this study to investigate various possibilities for using these procedures in herbicide absorption and translocation experiments.

Esters of the chlorophenoxyacetic acids are generally considered to be more phy to toxic than the acid or acid salts. Hence the esters have found wide use in herbicidal formulations. Much research has been done on the mode of action of plant growth regulators, but the fate of neutral derivatives of active acids has received little attention, even though an acid side chain is one of the molecular requirements for growth substance activity.

Several triazines exhibit high phytotoxicity towards many species of higher plants and are being extensively studied as possible herbicides. Moreland et al. and Exer reported that 2-chloro-4,6-bis(ethylamino)-s-triazine, simazine, inhibited the photochemical activity of isolated chloroplasts. Exer also presented evidence that the inhibited reaction involved the photochemical reduction of DPN, diphosphopyridine-nucleotide. Gast has shown that in Coleus Blunei Benth. simazine blocked starch production in the light and that this effect was overcome by the addition of sucrose to starch-free leaves in the dark. These results indicated interference of photosynthetic CO2 fixation by simazine. Roth reported that simazine inhibited photosynthesis in Elodea but had a stimulating effect on respiration. In light of these findings a study of the effect of simazine and certain related triazines on the photosynthetic CO2 fixation of red kidney bean was undertaken.

Halogeton glomeratus was first discovered in the United States growing in the vicinity of Wells, Nevada, in 1934–35. Since that time it has invaded Utah, Nevada, Wyoming, Montana, Colorado, Idaho, Oregon, and California. The total area it infests now exceeds 11 million acres.

Davis and Duke in 1955 reported successful use of a 36 lb ahg solution of the propylene glycol butyl ether ester of 2,4,5-T applied by means of a tree injector. This tool is essentially a modification of the Cornell tool described by Cope and Spaeth in 1931, and subsequently tested with ammonium sulfamate and 2,4,5-T.

Good plot sprayers are essential in weed control investigations where chemicals are to be applied uniformly and in specified quantities. Derscheid described such a machine in 1952 and this machine, or similar models, have been used quite widely. The purpose of this paper is to report on a sprayer which was built as an improvement on Derscheid's machine. A number of these modified sprayers have been built at Swift Current and used successfully by other weed workers in Canada.

The Russian thistle (Salsola kali L. var. tenuifolia Tausch) called in some parts of México “saladilla” is an important weed in the dry regions of the United States. It was introduced in 1873 or 1874 to South Dakota and from there migrated to the West and Southwest, reaching California between 1892 and 1895, where it constitutes a serious problem.