Water content and the effectiveness of hydro and osmotic priming of cotton seeds

The water content reached by seeds during priming treatments depends on the incubation conditions and seldom is this variable considered when analyzing the degree of success obtained by this treatment. The objectives of this investigation were to study the kinetics of imbibition of cotton seeds in water and in polyethylene glycol and to evaluate the effectiveness of the different treatments based upon the osmoticum used and the water content achieved by the seeds. Curves of imbibition in water and in polyethylene glycol -0.8 and -2.2 MPa were determined. Based on these curves, the durations of priming in water and in both concentrations of polyethylene glycol that achivied the same water content (7, 20, 30 and 40%) were selected for further treatments. Seed germination in water and under water stress (polyethylene glycol -0.8 MPa) was evaluated at 25°C and 16 h photoperiod. Hydropriming did not affect germination in water or under water stress. Osmotic priming reduced germination in both instances by increasing the length of the treatment and the concentration of osmoticum used. The inhibition produced by osmotic priming was more marked under water stress. For cotton seeds, osmotic priming with polyethylene glycol is not to be recommended and the effectiveness of the treatments does not depend exclusively on the priming water content.