Reducing Substances in Zostera

Abstract

DURING a study of the reduction of sulphates in Zostera mud flats, it was found that when autoclaved Zostera was added to autoclaved sand and sea water, ferrous sulphide was rapidly produced. At first it was thought that this reduction was microbiological, but later it was found that living Zostera could bring about the reduction. A study of Zostera showed that a lead mirror could be produced from lead acetate by heating this substance with Zostera leaves and that this mirror was intracellular in the leaf parenchyma. When washed Zostera leaves are heated with distilled water, cadmium acetate papers show yellow cadmium sulphide, and, at times, metallic cadmium. If the distillation is carried out under nitrogen, the steam distillate condensed into 100 ml. of N/1,000 hydrochloric acid at pH 3.35 yields a nitrogenous solution containing up to 6.75 mgm. nitrogen per litre, and the pH rises to 7.0 with a volume increase to 450 ml. In addition, there is a volatile sulphur-containing substance which is soluble in alcohol and produces lead sulphide from lead acetate. This sulphur compound gives no precipitate with mercuric chloride and a white precipitate with alcoholic lead acetate, suggesting a thioether. It has an unpleasant odour. The production of lead sulphide from lead acetate seems to depend on a partial volatilization of the nitrogenous base. Posidonia appears to contain a different sulphur derivative with a more pungent odour.