Dormancy‐Related Growth Inhibitors in Seeds of Orchardgrass ( Dactylis glomerata L.) 1

Summary Greater amounts (concentrations) of growth inhibitors were extracted from seed of dormant ‘Latar’ orchardgrass ( Dactylis glomerata L.) than from nondormant ‘S‐143’ orchardgrass. In Latar seed one‐third of the inhibitor was present in the lemma and palea and the remainder, in the caryopsis. On a per‐unit weight basis, however, the growth inhibitors are equally distributed between the hulls and the caryopsis. Storage of Latar seeds for 3 years did not significantly decrease the level of inhibitor. Chilling Latar seeds for 7 to 10 days at 5 C reduced the concentration (amount) of inhibitor to a level similar to that existing in nondormant S‐143 seed. Reduction of the inhibitor associated with Latar seeds by cold treatment of physical dehulling decreased their dormancy. Thus, the extent of dormancy appears to be regulated by the amount of growth inhibitors associated with the seed during germination.