High temperature contact treatment of hard seed in Stylosanthes

Abstract

Samples of hard seed of Stylosanthes humilis, S. hamata, S. scabra and S. viscosa were agitated on high temperature metal plates in order to reduce the hard seed content. The optimum temperature for reduction of hard seed was found to be 140–150°C, with a contact period of 15–30 s, and hard seed content was reduced by up to 70%. Internal seed temperatures generally remained below 70° during this treatment, and there was little loss of viability. As with percussion treatments, imbibition took place through the strophiole, which indicates that break of hard seed occurred by mechanical stresses fracturing the palisade cells at the strophiole.

On the basis of this principle of high surface temperatures and brief seed contact, a heated rotating drum was constructed and successfully used to treat bulk quantities of hard seed.