Flow Cytometric Determination of Nuclear Replication Stage in Seed Tissues

Abstract

Flow cytometric determination of DNA levels in embryos of fully matured seeds of various plant species revealed large amounts of 2C DNA signals, indicating that most cells had arrested the cell cycle at the presynthetic G 1 phase of nuclear division. The accumulation of cells at G 1 was found both in orthodox and in recalcitrant (i.e. Castanea sativa ) seed species. As recalcitrant seeds are characterized by the absence of maturation drying, the arrest of the cell cycle in the presynthetic phase may not be linked to the seed water status. Apart from the 2C signal, 4C values were found in the embryo of some seed species (e.g. Raphanus sativus ) indicating that cells were arrested in G 2 Cells arrested in G 2 were primarily located in the root-tip region of the embryo. In addition, combinations of higher C values (i.e. 8C, 12C, 16C and 64C) were observed in the endosperm of Solanum melongena and Lycopersicon esculentum , and in the root-tip cells of Phaseolus vulgaris and Spinacia oleracea . These mixtures of polyploid nuclei (also called 'polysomaty') may arise from a developmentally controlled cellular endoreduplication and indicates that in each cell type of the seed the amount of DNA is regulated both spatially and temporally. Copyright 1993, 1999 Academic Press