Seedling emergence of Lupinus diffusus in response to abrasion in an electric seed scarifier

Abstract

Lupinus diffusus Nutt. (Fabaceae) is a floriferous, nitrogen-fixing forb native to dry, infertile sites of the southeastern US with uses in restoration, as a low-input ornamental landscape plant, and as a cut flower. Seed propagation of this species requires pretreatments because of physical dormancy. Practical information regarding the alleviation of physical dormancy for this plant is lacking. A maximum of 41% seedling emergence of viable seed after exposure to 18M sulfuric acid for 60 min has been demonstrated for L. diffusus. We conducted preliminary laboratory germination experiments testing scarification techniques and found that both abrasion in an electric seed scarifier and hand-nicking seed testas were effective in alleviating physical dormancy. We then conducted a 33-d greenhouse seedling emergence experiment comparing scarification in an electric seed scarifier (0, 15, 30, 45, and 60 s) to hand-nicking for 2 Florida L. diffusus seedlots. We found that certain treatments in the electric scarifier (30, 45, and 60 s) were as effective as hand-nicking. In this study, we improved L. diffusus seedling emergence to 85% as compared to existing scarification techniques. Mechanical scarification for 45 s in an electric seed scarifier was as effective (76% emergence) as the prohibitively labor-intensive pretreatment practice of hand-nicking individual seeds (82% emergence).