Germination responses of Solanum aculeastrum, a medicinal species of the Eastern Cape, South Africa

Solanum aculeastrum is a highly valued medicinal plant which is under serious exploitation in the Eastern Cape. Seed germination requirements of this species was studied with the aim of producing appropriate germination protocols for use in its commercial cultivation as well as in ex-situ conservation. Effects of photoperiod, presoaking and prechilling treatments on germination were investigated. When the seeds were incubated under continuous darkness at alternating day/night temperatures of 18-25 degrees C, germination was less than 12% in all treatments. On the other hand, above 60% germination was obtained in all treatments under illumination, indicating that S. aculeastrum seeds require light as a cue for germination. Prechilling and presoaking in water did not significantly improve the final germination percentage of the seeds. However, soaking seeds in water was found to increase the germination rate. The present study demonstrates the possibility of ex-situ propagation of S. aculeastrum from seeds. The best condition for the germination is one day presoaking in water followed by exposure to illumination under day/night temperature of 18-25 degrees C. This investigation also shows that presoaking or prechilling treatments cannot satisfy the light requirement factor for successful germination in this species.