Germinação sob restrição hídrica de sementes de espécies florestais condicionadas

Abstract

Seed germination of some forest species presents obstacles during its process. Thus, pre-germination treatments are essential to improve germination, with priming being a technique widely used to improve uniformity and increase germination speed. In view of this, the objective of this study was to evaluate the effect of physiological conditioning on seed germination of two forest species (Handroanthus heptaphyllus and Enterolobium contortisiliquum) under water restriction. Initially, the imbibition curves of the seeds were built at 20 °C in water (0.0 MPa) and in PEG 6000 solution (-0.4 MPa). Subsequently, the seeds were subjected to physiological conditioning in water and in PEG solution (-0.4 MPa) at 20 °C, and then placed to germinate in water and in PEG solutions at potentials of -0.2, -0.4 and -0.8 MPa. Final percentage of germination, Germination Speed Index (GSI), Average Germination Time (AGT) and time to reach 50% germination (T50) were evaluated. Data were submitted to analysis of variance by F test and Tukey's test at 5% probability using the Rstudio program. Seeds of H. heptaphyllus 2018 showed a higher percentage of germination after hydroconditioning, while those from 2019 showed no formation of normal seedlings when placed to germinate at the potential of -0.8 MPa. When conditioned in PEG, E. contortisiliquum seeds 2008 showed a lower percentage of germination at -0.2 MPa water potential. For the seeds of both species, GSI was higher when they were placed to germinate without water restriction, except for H. heptaphyllus 2018 at -0.2 MPa potential, which showed a higher GSI value in osmoprimed seeds, contributing to a faster seed germination. Seeds conditioned in PEG did not form normal seedlings at -0.8 MPa potential. The most severe water restriction significantly reduced the germination of H. heptaphyllus 2018 seeds conditioned in PEG and placed to germinate at -0.4 and -0.8 MPa. Osmopriming increased seed germination of E. contortisiliquum 2008 only at potentials of -0.4 and -0.8 MPa, but did not contribute to the formation of normal seedlings.