Embryo immaturity associated with delayed germination in recalcitrant seeds of Virola surinamensis (Rol.) Warb. (Myristicaceae)

The study aims to test the hypothesis of embryo dormancy caused by immaturity in Virola surinamensis seeds was investigated as a result of observations of a low germination rate of freshly collected seeds shown in previous studies. Recently dispersed seeds were kept in a substratum of moist vermiculite at 25°C, for 45 days. Data on water flotation, diameter, length and weight of 10 seeds were obtained at 10 day intervals. Size of embryo (cotyledons and hypocotyl) was determined by direct mensuration. Most of the seeds that sank (69%) had a degraded embryo and/or endosperm. Germination started on the 35th day and was characterised by protusion and growth of radicle. Diameter and weight of seeds decreased with time after sowing. The size of the cotyledons increased from collection (μ = 1.0 mm) to the 20th day from the beginning of the tests (μ = 3.4 mm). The total size of embryo also increased, from 2.0 mm to 5.0 mm. The hypocotyls, however, did not show any signs of growth. Virola surinamensis has haustorial type cotyledons, which consume endosperm reserves as they grow, that could promote reduction of seed weight and diameter. Data obtained showed that there was growth of the embryonic axis and that it had to reach a size over 4.0 mm (cotyledon > 2.5 mm) before germination would occur. Thus the embryo is immature at seed dispersal, causing a delay, which could be described as a short dormancy in the recalcitrant seeds of V. surinamensis.