Osmotic stress in the germination of Samanea tubulosa (Benth.) Barneby & J. W. Grimes seeds

Abstract

The objective of this work was to evaluate the effects of four osmoregulators under different concentrations on seed germination and seedling growth of Samanea tubulosa. The seeds were placed in gerbox and moistened with 20 mL of the following solutions: mannitol, PEG-6000, NaCl and KCl, in osmotic potentials 0.0; -0.3; -0.6; -0.9 and -1.2 MPa. At the end of the experiment, GI and GIS calculations were performed. The seedlings considered normal were selected to measure fresh mass, dry mass, root and shoot length. It was observed that the treatment with PEG-6000 was the one that presented the greatest changes in the GI and GIS obtaining a reduction of 81% in the germination already in the concentration of -0.3 MPa. With mannitol, the greatest effects on the reduction in germination were only observed from -0.9 MPa. The treatments with NaCl and KCl obtained similar behaviors. The control presented the highest percentage of normal seedlings, while the treatment with -0.3 MPa of KCl showed root growth 22% and shoot 14% higher than the control. At the end of the experiment, it was observed that the seeds and seedlings of Samanea tubulosa are moderately tolerant to stress caused by NaCl and KCl, however, they are slightly sensitive to the stress caused by mannitol and extremely sensitive to the stress caused by PEG-6000. Furthermore, it was concluded that for the studied species mannitol was not efficient in simulating water stress, being recommended PEG-6000 to simulate this stress in future studies.

Keywords:
Bordão-de-velho; Water stress; Salt stress; Forest seeds