THE PHYSIOLOGY OF CONVOLVULUS ARVENSIS (MORNING-GLORY OR BINDWEED) IN RELATION TO ITS CONTROL BY CHEMICAL SPRAYS

Abstract

(a). The reaction of plants to chemical sprays, and the effectiveness of these sprays, depend upon penetration and subsequent distribution of the chemical throughout the living tissues. This paper reports some experiments relative to the factors which control these processes in the wild morning-glory (Convolvulus arvensis). Early writers (3, 5) on morning-glory control prescribe clean cultivation, pasturing, and the use of smother crops. That these methods were unsuccessful in the hands of practical farmers was recognized in California in 1915 ; and in the fall of that year George P. Gray (8) started a series of experiments on the use of chemical sprays. A number of plant poisons were used but the application of sodium arsenite solution to the leaves of mature plants was the only treatment which he found successful. Recommendations were made (7) for the use of this spray in the coastal fog belt of California, but it was not extensively used by farmers. The materials were dangerous to handle and the treatment allowed the maturing of a crop of seed before the application of the spray, making eradication practically impossible. Gray proved that the perennial roots of the morning-glory could be killed by the application of arsenic to the leaves. He realized the importance of this fact and emphasized the need for further study of the problem as the mechanism responsible for the distribution of the arsenic within the plant was not understood at that time. Few of the workers after Gray have followed his suggestion. Publications from the United States Department of Agriculture (17), California (2), Utah (16), and Colorado (14), adhere to the older recommendations. The Colorado workers (14) found no evidence for translocation of arsenic in their experiments with K.M.G.1 Better results were obtained with this product in Washington (15) but it was not completely satisfactory. The present study was started in 1925 for the purpose of determining the mechanism responsible for the translocation of arsenic within the morning-glory plant. Continued attempts to control this weed by cultiva-