The Formation of Polyploid Cells in Ripening Cotyledons of Pisum sativum L. in Relation to Ribosome and Protein Synthesis

Abstract

The present paper deals with the formation of polyploid nuclei and the synthesis of RNA and protein in the parenchyma cells of developing cotyledons of Pisum sativum L. During seed formation these cells synthesize large amounts of reserve proteins and starch, which later on are used up by the embryo during seed germination. The changes of the amount of DNA per cell in the ripening cotyledon tissue have been estimated by Feulgen histophotometry. The amounts of DNA, RNA, and protein in the whole cotyledons have been estimated by chemical methods. In this way it was possible to correlate the fluctuations of the amount of DNA, RNA, and protein with changes at the cellular level. During a preparatory phase, preceding the phase of real cell expansion and intensive accumulation of seed globulins and starch, the storage cells attain a high level of polyploidy: nuclei with up to a 64 C DNA content are formed. The results indicate a correlation between the high degree of polyploidy in the parenchyma cells of the cotyledon and the high rate of RNA and protein synthesis (seed globulins) in this storage organ (gene dosage effect).