Glycinebetaine, γ-aminobutyric acid betaine and δ-aminovaleric acid betaine have been isolated from four commercially-produced seaweed extracts. A reliable proton magnetic resonance spectroscopic assay method for the estimation of all three compounds has been developed. High performance liquid chromatography using low wavelength ultra-violet light detection was found to be unsuitable for the analysis of betaines in seaweed extracts, even after partial purification by passage through columns of ion-exchange resin. A microbiological assay procedure was also utilised based on measuring the grov/th of Klebsiella pneumoniae produced by the addition of seaweed extracts to a medium with a growth-inhibitory concentration of sodium chloride. The concentrations of betaines found in the extracts when determined by the *H NMR spectroscopic method were too low to account for all of the anti-stress related effects reported for seaweed extracts after their application to plants. However, the microbiological assay results indicate that the extracts contain, in addition to betaines, other components which play a significant role in overcoming osmotically-induced growth Inhibition of K. pneumoniae.

With fourteen Figures In the Text. INTRODUCTION.T HE immediate object of the studies reported in the present paper was to obtain information concerning both the external and the internal factors responsible for the premature shedding of the flower-buds and the young fruit (bolls) of the cotton-plant in St. Vincent. The economic importance of premature abscission is not, of course, confined to the cotton-plant, for it is responsible for considerable losses in a large number of cultivated plants. Future investigation may reveal how far the conclusions arrived at in the course of the present work are of wider application.Before reporting the results, reference should be made to the conclusions of previous investigators of the problem. The work of Balls (1) in Egypt established a strong presumption that the major factor initiating abscission was a marked water-deficit in the body of the plant. It was found that the elongation of the stem of the cotton-plant was checked immediately the sun struck upon it, and that a slight shrinkage usually followed. A cloud passing across the sun, for instance, was effective in permitting growth, which ceased again as soon as the sun emerged. Balls's conclusion that a net loss of water was the direct cause of growth-inhibition and boll-shedding received confirmation from Lloyd's (6) studies, which were conducted under the relatively humid conditions of Alabama. Ewing's (2) work in Mississippi also indicated that a disturbance in the water-balaqce of the plant was the main factor responsible for shedding. In St. Vincent, where cotton is probably cultivated under more humid conditions than elsewhere, Harland (3) noted that shedding was heaviest after torrential rain. His observations led him to conclude that root absorption was interfered with as a result of the reduction in the oxygen-

No abstract

No abstract

No abstract