Screening of seed germination requirements of some native plants of the Mediterranean region

In the present study, we aim to investigate the seed germination conditions of three Lamiaceae widespread in the Mediterranean region and growing spontaneously in Algeria: Marrubium vulgare L., Rosmarinus officinalis L. and Thymus algeriensis Boiss. et Reut. Two experiments were carried out: (i) Ex vitro germination test: without pre-treatment. Species seeds were sowed directly in the soil under continuous darkness at 4 degrees C, room temperature (23 +/- 2 degrees C), photoperiod (16 h/light/25 +/- 1 degrees C, 8 h/dark/15 +/- 1 degrees C) and in open green house conditions. (ii) In vitro germination test was achieved by incubating sterile and soaking seeds in various doses of gibberellic acid (GA3) (0, 125, 250, 500 mg/L) under photoperiod (16 h/light/25 +/- 1 degrees C, 8 h/dark/15 +/- 1 degrees C) and continuous darkness (16 h/dark/25 +/- 1 degrees C, 8 h/dark/15 +/- 1 degrees C).In ex vitro experiment, results showed that the combination of darkness and cold, ambient temperature and photoperiod did not present any significant effect (P > 0.05) on germination success rate (GSR) in the three tested species. However, low GSR (23.3%) was observed in both Thymus algeriensis and Marrubium vulgare when seed samples were placed in a greenhouse. An effective sterilization protocol was developed to successfully germinate seeds under in vitro conditions where mercuric chloride (HgCl2) was used as the most powerful sterilizing agent. In in vitro experiment, Thymus algeriensis seeds presented high GSR (66.7% to 83.3%). Furthermore, the application of GA3 at 125, 250, 500 mg/L and continuous darkness resulted in significantly high GSR (P < 0.001) in Marrubium vulgare with 68.3%, 71.6%, 73.3% and 71.7%, respectively. The interaction of GA3 at 125 mg/L and darkness significantly increased the GSR to 93.3%. In addition, GA3 doses, photoperiod-dark and the interaction GA3 x phoroperiod-dark significantly influenced the germination speed (P < 0.001) in Marrubium vulgare. While, all the treatments: GA3 doses, photoperiod-dark and their interactions did not significantly affect the seed germination (P > 0.10) in Rosmarinus officinalis, which showed a very low GSR (6.7%).

Automated summary

The aim of this study was to investigate the seed germination conditions of three Lamiaceae species in Algeria. Two experiments were carried out: ex vitro and in vitro germination tests. In the ex vitro experiment, the combination of different conditions did not have a significant effect on germination success rate (GSR) in all three species. In the in vitro experiment, Thymus algeriensis showed high GSR, while Marrubium vulgare had significantly high GSR with the application of gibberellic acid (GA3) at certain doses and continuous darkness. Rosmarinus officinalis had a very low GSR regardless of the treatments used.