An efficient method to overcome seed dormancy in Scotch broom (Cytisus scoparius)

Abstract

Seeds of many wild members of the Leguminosae and Solanaceae have hard seed coats which restrict water absorption by the embryo. Failure to imbibe limits O<inf>2</inf> to the embryo and leaching of inhibitors, therein effectively enforcing dormancy of the embryo. For applied uses, dormancy-breaking treatments are required to provide more uniform and rapid seed germination responses. Permeability may be improved by scarifying the seed coat by mechanical means (e.g. clipping, abrasion or immersion in hot water) or chemically with strong oxidative agents (e.g. sulfuric acid, sodium hypochlorite). In either case, results obtained are often less than satisfactory and commonly a fraction of the seeds are damaged, significantly reducing the overall viability of the seed lot. An improved method of propagation from seed is desirable. We report here a simple, yet effective means to overcome dormancy in Scotch broom, a plant with potential value in dune erosion control. Sequential, rapid immersion in hot water followed by liquid nitrogen dramatically improved seed imbibition and germination responses by as much as 3.5 fold. The most effective immersion times and sequence of pretreatments were identified. The strategy outlined in this paper may be widely applicable to improving seed propagation of recalcitrant species. © 1989.