Factors influencing seed germination of Coleonema album – an aromatic and medicinal plant

Coleonema album (Rutaceae) is restricted to the mountains and coastal region of the Western Cape Province of South Africa. The plant has good economic potential due to its aromatic and medicinal properties and the leaves, which contain essential oils, are used for repelling insects. Exploitation for commercial purposes and propagation through seed remains the best option to grow and perhaps conserve this species. However, scientific information on its seed biology and germination is inadequate. This study highlights the effects of temperature, temperature shifts, light, pH, sodium chloride (NaCl) and ammonium nitrate (NH₄ NO₃) on seed germination of C. album. At 20, 25, 30, 35 and 30/15°C, no seeds germinated, but at 15°C they germinated under both alternating light (16-hour photoperiod; 45%) and constant dark (47.5%). When seeds were shifted from 20, 25, 30, 35 and 30/15°C, to 15°C after 90 days, germination improved significantly in both constant darkness and alternating light conditions. Buffer of pH 6 and 10^-2 M of NaCl and NH₄ NO₃ significantly (P < 0.05) increased germination in constant dark conditions at 15°C. Findings of this study will assist growers to propagate C. album plants.