[Patterns in the cellular organization of ovule growth in the pine, Pinus silvestris L. I. Growth processes in...

The dynamics of growth processes was studied in the endosperm of Pinus silvestris during the year of fertilization. The growth of endosperm is described by an diauxic curve where the period of delay corresponds, by time, to fertilization. The growth of tissue proceeds, mainly, at the expense of cell proliferation. The mitotic activity is preserved in the endosperm till the beginning of formation of reserve substances in the cells; cell division and elongation occur simultaneously. The unfavourable environmental conditions influence the mitotic activity of cells only. The size of fully grown cells is relatively constant and somewhat decreases later, during maturation. One can distinguish rather early those regions in the endosperm where the cell size is 2-3 times less than in the rest tissue; the size of cells and nuclei in these regions suffers only insignificant changes during the growth. The large nuclei are observed in the beginning of the cell endosperm formation and, then, their size decreases 1.5-2 times; the second increase in nuclear size in the endosperm is observed during the period prior to the formation of reserve substances.