Seed germination during floatation and seedling growth of Carapa guianensis, a tree from flood-prone forests of the Amazon

Abstract

Carapa guianensis Aubl. (Meliaceae), a hard wood tree from the Brazilian Amazon, has large recalcitrant seeds that can germinate and establish in both flood-free (terra-firme) and flood-prone (varzea) forests. These seeds, although large, can float. This study was designed to experimentally examine seed longevity under floating conditions ex-situ and its effects on subsequent germination and seedling growth. Many seeds germinated while floating, and radicle protrusion occurred from 3 to 42 d after the start of the floating treatment (tap water, room temperature 20–30 °C). Shoots of newly germinated floating seedlings may elongate up to 37.0 cm in 20 d without loss of viability. Epicotyl and first leaf emergence were delayed by floating. Seeds that did not germinate while floating were then placed on vermiculite and watered daily, where many seeds resumed germination. Germination during and after floating was affected by the length of the floating treatment: 88% germinated after 1 mo, 82% germinated after 2 mo and 70% germinated after 2.5 mo. These results indicate that Carapa guianensis has physiological variation regarding dormancy in response to seed floatation. The fact that floatation induces dormancy in recalcitrant seeds of this economically important species can be relevant to initiatives of ex situ storage of seeds.