Studies in Plant Metabolism

The nutrition of plants has been studied with reference to the identification of nutritional abnormalities by chemical analysis of tissue, and the methods evolved have been utilised in the study of a nutritional disease of the tomato plant. A more detailed summary is given below. 1) A review of the diagnosis of nutritional abnormalities by plant analysis, and of the sampling technique and treatment of tissues associated with such analysis, has been given. The methods developed in this research work have been described. 2) Methods of determination of calcium, magnesium, potassium, nitrogen, phosphorus, chlorine and sulphur have been examined.and some have been adapted, and others evolved, for use with tissue extracts. The determination of magnesium has been especially studied. 3) Certain methods of soil analyses have been discussed and described. 4) A disease of the tomato plant has been described and an account has been given of certain preliminary investigations investigations which suggested that the disease was due to a deficiency of magnesium in the plant, though not in the soil. A potassium : magnesium antagonism has been suspected of preventing the plant from absorbing adequate amounts of magnesium. 5) The plant-analysis technique has been used not only in the straightforward investigation of the disease but also in determining precisely the effects of treatments. The connection between the disease and a low magnesium content of the plant tissue, particularly the laminae of the lower leaves, has been clearly shown. Though the disease has often been associated with a high potassium content of the tissue, there has been no need to take into account the potassium : magnesium ratio in the tissue when considering the incidence of the chlorosis. It has been shown that the chlorosis was not premature senescence and that on resoiling, the outstanding effect on the uptake of nutrients was in increasing the absorption of magnesium. 6) The absorption of ions and the potassium : magnesium, antagonism have been reviewed and have been correlated with the results obtained from sand-culture and soil experiments. High potassium : magnesium ratios and high osmotic pressures in the rooting media have been shown to reduce the absorption of magnesium by the plants, the former being the more important and being particularly active with high osmotic pressures. Certain other ion relationships have been investigated and discussed. 7) Control of the disease by adding magnesium