Endopolyploidy and chloroplast numbers in different cell types of trisomic sugar beets

Abstract

Earlier investigations were continued on cell specific effects of eight different extra chromosomes in single trisomic sugar beets (Beta vulgaris L.). The degree of endopolyploidy, which was determined approximately by means of chloroplast numbers per cell, was changed by the presence of certain extra chromosomes: it either increased (I, II, VIII) or decreased (III through VII), but in epidermis and in spongy parenchyma the change was in the same direction. Sometimes, however, the degree was found to increase in spongy parenchyma alone or to decrease in epidermis alone; this evidence is consistent with the generally low liability of the epidermis to endopolyploidization. Independently of endopolyploidy the basic number of plastids (i.e., the amount reached in a cell type under given conditions, but without endopolyploidy) was altered in certain trisomes: it was higher (with extra chromosomes III through VI) or lower (II, perhaps also I) than in eudiploid control plants, the change taking the same direction in epidermal and in spongy parenchyma cells as in guard cells.