Germination of the succulent, invasive species Kalanchoe delagoensis

Background/Question/Methods

Biological invasions constitute a major threat to global diversity because invasive species can compete with or displace native species. Clonality is a common feature among invasive plant species because promotes long-distance dispersal and local persistence. Kalanchoe delagoensis, a succulent plant native to Madagascar, was introduced to the American continent for ornamental purposes and it rapidly became invasive due to its ability to clone through plantlets. This species reproduces clonally in several Mexican populations; however, certain populations reproduce sexually through seeds as well, which may promote its persistence in the wild. We studied seed germination of K. delagoensis from a population located in Tamaulipas, Mexico. Seeds were collected on March 2011 from withered inflorescences. We explored whether seed age affects germination ability by sowing seeds five and eight months after collection. Each trail was conducted under two temperature conditions (25ºC constant and 16-25ºC fluctuating) and two light conditions (white light and darkness). Each treatment consisted of twenty replicates, with fifty seeds per Petri dish with 1% bacteriological agar. Germinated seeds were counted every other day during 30 days and finally the final germination percentage was obtained.

Results/Conclusions

Results showed that seeds are positive photoblastic, because there was no germination under darkness conditions regardless of the temperature. For five month seeds, germination percentages under light conditions were 49.4% and 45.4% for constant and fluctuating temperature, respectively. Germination percentages under light conditions for eight month seeds were 43% for constant temperature, and 26.24% for fluctuating temperature. The fluctuating temperature delayed the onset of germination and made germination asynchronous, compared to the constant temperature. The percentages obtained were high compared with other species from Crassulaceae. This germination success may also potentiate invasiveness in this species, broadly regarded as completely clonal. However, these results showed that germination success decreases with increasing seed age.