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Water is one of the factors that most influences the seed germination process; however, its excess can cause injuries to cell membranes due to rapid imbibition. On the other hand, water restriction limits seed germination, promoting a reduction in cell water potential that disrupts physiological and metabolic reactions. Thus, the objective of this study was to evaluate the physiological quality of sunflower seeds subjected to water stress induced by polyethylene glycol 6000 (PEG 6000). The experimental design used was completely randomized, consisting of six treatments consisting of osmotic potentials (0; -0.3; -0.6; -0.9; -1.2; and -1.5 MPa) simulated with aqueous solutions of PEG 6000. Germination, radicle protrusion, first count, germination speed index, abnormal seedlings, shoot length, and root length were evaluated. Water stress induced by PEG 6000 solutions affects the physiological quality of sunflower seeds, being proportional to the reduction of osmotic potential. Germination and seed vigor decrease under water stress conditions from an osmotic potential of -0.4 MPa, with the most negative potentials (-1.2 and -1.5 MPa) preventing seed germination.
Santos et al. (Wed,) studied this question.