Studies on Agriculturally Important Plant Metabolites

This thesis deals mainly with the carbohydrate metabolism of plants, and in particular with that of bracken and of potatoes. Four main projects are described: a) An investigation into the seasonal and other variations in carbohydrate levels in bracken rhizomes, which is relevant to the behaviour of herbicides in the plant and to its ability to withstand herbicide treatment. b) Examination of the glycolipid and phospholipid composition of bracken, initially to determine whether any glycolipids which could act as intermediates in polysaccharide biosynthesis might be present. None were found, but the results have implications for the composition of plastid membranes and the turnover of carbohydrates in photosynthetic tissue. c) A parallel investigation on carbohydrates and lipids in potato tubers during low-temperature storage, with a twofold objective: firstly to investigate the mechanism of low-temperature sweetening and the role of membrane lipids therein, and secondly to compare commonly-grown varieties in their tendency to accumulate sugars at low temperatures. d) The partial characterisation of a complex mucilaginous polysaccharide found in bracken. The significance of the results for carbohydrate metabolism in bracken and other plants; the storage of potatoes for processing; and bracken eradication techniques is discussed, and some observations on the ecology of bracken and its effects on the soil are presented in two appendices