Germination and Radicle Growth Characteristics of Presowing-treated Carrot Seeds Affected by Different Moisture Levels.

Abstract

Germination of imbibed and primed carrot seeds, and seedling radicle growth of im- bibed, primed, pregerminated, and primed + pregerminated seeds were compared with those of untreated seeds under different osmotic potentials.Percentage germination decreased significantly at -1.0 MPa in untreated seeds and tended to decrease in imbibed seeds. However, percentage germination of primed seeds did not decrease at -1.0 MPa. It was suggested that sensitivity to water stress of germi- nability could be lowered as pregermination stage was advanced.Mean germination time for untreated and imbibed seeds increased as osmotic potentials were lowered. Relative increase in mean germination time caused by lowering osmotic potentials was greater for imbibed seeds than it was for untreated seeds. However, mean germination time of primed seeds did not increase at osmotic potentials up to -0.4 or - 0.6 MPa. A difference in response to water stress of germination time between primed and imbibed seeds may be caused by cellular opposite osmotic adjustment during these presowing treatments.Coefficients of variation in germination time had no consistent trend against osmotic potentials.Elongation rates of seedling radicles decreased at osmotic potentials below -0.4 MPa for untreated and imbibed seeds, and below -0.2 MPa for primed, pregerminated, and primed +pregerminated seeds.