DNA synthesis and mRNA accumulation during germination of embryos of the orchid Spathoglottis plicata

Abstract

Germination of embryos of the orchid, Spathoglottis plicata Blume involves the formation of a protocorm in which DNA synthesis and cell divisions are confined to the proximal end whereas cells at the distal end undergo enlargement. Although3H-thymidine was incorporated into the distal cells of the embryo during the early period of germination, DNA synthesis was not followed by mitosis and cytokinesis. Poly(A)-RNA detected by in situ hybridization of sections to3H-poly-(U) was present uniformly in all cells of the embryo of the dry seed. However, coincident with the formation of the apical meristem, there was an increase in the density of auto-radiographic silver grains in the cells of the embryo, with a concentration of silver grains in the proximal part. The results indicate that regulatory events in the embryo prior to seed maturity determine the fate of its proximal and distal parts during germination. © 1994 Springer-Verlag.