Enhanced seed germination of three Aristolochia species using light, karrikinolide and GA 3

Aristolochia species form a large taxon and are used as traditional medicines. There are very few reports on seed germination of Aristolochia species. In this study, the effects of light and karrikinolide (KAR1) (1–100 nM) on seed germination of three sympatric Aristolochia species ( A. labiata , A. debilis and A. ringens ) from South China were investigated. The shortest germination period of the three species treated with both light and KAR1 was 8, 12 and 18 d, respectively. The percentage of seed germination in light was higher than in the dark in all three species, indicating that the seeds were light-sensitive and physiologically dormant. In the dark, the seeds of A. labiata and A. ringens could not germinate while only some A. debilis seeds germinated. After treatment with KAR1, A. debilis and A. labiata seeds germinated at a low frequency in the dark. However, A. ringens seeds could not germinate, even when exposed to a high concentration of KAR1. To investigate a possible functional mechanism of KAR1, A. labiata seeds were treated with 100 µM of some plant growth regulators, indole-3-acetic acid (IAA), abscisic acid (ABA), kinetin (KIN), gibberellic acid (GA 3 ) and KAR1 (100 nM), and placed in the dark. Although the KAR1 + GA 3 combination stimulated some seed germination, the seed germination in response to KAR1 and GA 3 was not as efficient as in light. KIN, ABA, and IAA did not induced any seed germination in the dark.