The Effects of Light and Temperature on Germination of Stevia (Stevia rebaudiana BERT.) Seeds

The Stevia rebaudiana (Bert.) Bertoni is a perennial herbaceous plant and belongs to family of Asteraceae (Compositae). The contents of S. rebaudiana (Bert.) Bertoni consist mainly non-caloric stevioside and rebaudioside A sweeteners. Low seed germination is an important problem in stevia cultivation. Therefore in this study, the effects of light and temperature on germination performance of stevia seeds were studied. Stevia rebaudiana seeds were treated with two lights (light/darkness) and four different temperatures (15 oC, 20 oC, 25 oC, 30 oC). For each treatment, 50 seeds were counted and placed into petri dishes. Experiments were conducted as a randomized complete design method with three replicates. Germination was started within 6 to 10 days depending on the treatments. The highest seed germination rate (71%) was observed in darkness/25 oC temperature and followed by darkness/20 oC (68%) and light/25 oC (67%). On the other hand, the lowest seed germination rate (31%) was obtained from 15 oC in both light and dark conditions and followed by darkness/30 oC (43%) and light/30 oC (49%). The results showed that lower (15 oC) and higher (30 oC) temperatures significantly decreased the germination rates of stevia independently from the light treatments.