Seed Imbibition of Five Brazilian Native Tree Species

Seed imbibition is basically determined by seed chemical composition, seed coat permeability and water availability for the process. The goal of this research was to evaluate the effects of seed protein content and water availability in the imbibition process of Acacia polyphylla, Guazuma ulmifolia, Mimosa bimucronata, Psidium guajava and Schinus terebinthifolius seeds. Seed imbibition was evaluated in deionized water and in three different osmotic potentials (44, -0.8, and -1.2 Mpa), obtained by using PEG 8000 solutions. The seeds were imbibed on three layers of blotter paper, soaked with either water or the different PEG solutions, at 20 degrees C with constant light. Each treatment consisted of four replicates of 100 seeds each. Seeds were weighed periodicatly, until either more than 10% of them had primary root protrusion or the moisture content stabilization. The protein concentration was analyzed based on Bradford's method. In water, A. polyphylla, G ulmifolia, M, bimucronala, R guajava and S. terebinthifolius seeds took 52, 84, 64, 324 and 176h, respectively, to start primary root protrusion, and at this moment, seed moisture content (wet basis) was 50.7, 39.0, 62.2, 25.6 and 56.4%, respectively. In PEG solutions, primary root protrusion was only observed for A. polyphylla. There was a positive proportional correlation between the protein concentration in the seeds and the critical moisture content required for germination. Thus, these results not only reinforced the importance of the evaluated factors for seed imbibition, but also established specific values for the tested species.