An Analysis of the Factors Controlling the Germination of the Seed of the Oil Palm, Elaeis guineensis (Jacq.)

Abstract

Under natural conditions in West Africa at the average ground temperatures of 25-30° C, oil-palm seed germinates sporadically over a period of years, but with continuous heat treatment (38-40° C.) 50 per cent, germination of either nuts or extracted kernels occurs within a few months. The kernel comprises a small cylindrical embryo embedded in a mass of oily endosperm which in turn is surrounded by a thick testa. At germination the testa and layer of endosperm covering the distal part of the embryo are forced out as a disc-like operculum which is already demarcated in the ungerminated kernel by a circular abscission zone in the endosperm cells. The excised embryo is non-dormant and at 30° C. starts to elongate within 24 hours, either on moist filter paper or while still in contact with the endosperm. At 30° C. removal of the operculum is followed by sluggish emergence of the embryo in air; emergence at the normal rate occurs in pure oxygen, or in air if a long period at high temperature precedes de-operculation. Fresh intact kernels remain ungerminated for at least 6 months at 30° C, either in air or in pure oxygen. At high temperature (40° C.) intact kernels germinate faster in pure oxygen than in air; at 30° C. the same applies only after previous treatment at high temperature. This accelerating effect of oxygen is shown to be dependent upon the progress of slow processes stimulated by high temperature. It is postulated that germination of oil-palm seed is dependent upon a minimal threshold concentration of oxygen in the embryo and that during dormancy this minimal level progressively decreases at a rate depending on the temperature.