Growth and accumulation of mineral elements in the axis of young pea (Pisum sativum L.) seedlings

Changes in fresh and dry weight, total nitrogen, protein nitrogen, phosphorus, potassium, and sulphur, have been followed in the shoot and in the root of young pea seedlings grown under a variety of growth conditions. It is shown that light inhibited shoot elongation, transport of reserve materials from the cotyledons, and acropetal transport, but enhanced net protein synthesis both in the shoot and in the root, and accumulation of mineral elements in the root. Treatment of the seedlings with gibberellic acid (GA) partly lifted the growth inhibition caused by light and shifted the nitrogen metabolism close to that of dark-grown seedlings, but did not affect transport from the cotyledons and only slightly the internal distribution of minerals. Competition between the shoot and the root from light-grown seedlings for the reserve minerals studied is not established until the end of the second week. The extent of secondary transport depends on the element considered. Potassium appears to be highly immobile once deposited, under the conditions of these experiments, while sulphur is the most mobile, nitrogen and phosphorus behaving in an intermediate way. Although the amount of acropetal transport depends on the growth conditions and age of the seedlings, the influence of these variables is non-specific, as indicated by the constant proportion in which the different elements are transported to the shoot.