Action spectra for light-induced germination in dormant lettuce seeds : II. Blue region.

Light of wavelengths in the range 400-500 nm induces germination of seeds of Lactuca sativa L. (cv. Noran and May Queen) when made light requiring by high temperature (thermodormancy) or prolonged exposure to far red light (far red dormancy). TD seeds proved more sensitive to blue light than FRD seeds by several orders of magnitude. Blue induced germination could be reversed by far red. Fluence response curves for this reversion are less steep for TD than for FRD seeds. The degree of germination of TD seeds after moderate doses of blue light is decreased by dark storage at 22° C or by exposure to far red and this is accompanied by a marked change in the shape of the fluence response curves. In these respects, germination induction by blue resembles that by red light. Continuous exposure to blue light inhibits germination of TD seeds but hardly that of FRD seeds. An action spectrum is given for blue induced germination of TD seeds.