Thiourea Solution Temperature and Bitterbrush Germination and Seedling Growth

Abstract

Antelope bitterbrush (Purshia tridentata (Pursh) DC.) seed is commonly soaked in a solution of thiourea to break seed dormancy for spring planting. "Warm" thiourea solutions have been reported to cause seedling deformities. To determine what range of "warm" temperature solutions can cause deformities, four seed collections were treated at 18 temperatures (30 degrees F to 200 degrees F) in increments of 10 degrees F. Normal germination and seedling growth resulted between 60 degrees F and 140 degrees F. Below 60 degrees rate of germination declined slightly, but seedling growth was normal. Seedling deformities began to show up above 140 degrees F, and germination decreased rapidly. Deformities consisted of annular cracks around the hypocotyls and detached root caps. Solution temperatures between 60 degrees F and 140 degrees F are recommended.