Changes in the carbohydrates, proteins and nucleic acids during seed development in opium poppy

Abstract

This investigation is concerned with the major changes in the levels of carbohydrates, proteins, nucleic acids and some enzymes in the ovules of Papaver somniferum at various stages of seed development. Of the soluble sugars, fructose and glucose are present in large amounts up to the free nuclear stage of the endosperm but decrease rapidly when the latter turns cellular; then sucrose becomes most abundant. At this time the concentration of insoluble carbohydrates is almost one-seventh that of soluble and the activities of α- and β-amylases are at their highest. The nitrogen in the seed is accumulated in two phases, the first coinciding with the development of endosperm and the second with the development of embryo. Cell wall formation in the coenocytic endosperm is accompanied with a marked decrease in the soluble nitrogen. The activity of glutamic-alanine transaminase increases concurrently with the increase of protein in the ovules. The maximal RNA content is attained after the ovules have completed their increase in size but prior to the deposition of proteinaceous reserves in the endosperm. The amount of DNA increases with the growth of endosperm but decreases during the maturation of embryo. Both ribonuclease and deoxyribonuclease show two pH optima corresponding to pH 5.5 and 7.5 (ribonuclease) and 5.0 and 7.5 (deoxyribonuclease). Their activities seem to be correlated to the levels of nucleic acids.