Optimizing allelopathy screening bioassays by using Tagetes sp. - water absorption capacity of the seeds

The aim of the present study is to: i) analyze the water absorption capacity of seeds of some Tagetes sp.; ii) compare the water absorption of Tagetes sp. and Lactuca sativa L. seeds in order to assess the potential of genus Tagetes as test object for laboratory screening studies for establishing allelopathic interference in plant communities. Tagetes erecta (local population from Germany), Tagetes patula (local population from Germany), and Tagetes patula variety “Usmivka” (Bulgarian variety) have been included in the study. Equivalence in the water absorption capacity (Ws%) of the seeds of studied Tagetes sp. and Lactuca sativa L. variety “Great Lakes” was found, with the maximum of water absorption occurring at the first hour and stopping by the fourth hour, regardless of the temperature range in which the imbibition takes place. The significant differences in the cumulative values of the average water absorption capacity of the Tagetes sp. seeds compared to Lactuca sativa L. variety “Great Lakes” (Ws% average ranged from +5.68 to +83.27%), indicate that the species of genus Tagetes can be successfully used in laboratory screening studies to establish allelopathic interference under in vitro conditions. Further research is needed to establish seed water absorption capacity (Ws%) of Tagetes sp. depending on the type of aqueous extracts used in allelopathic studies (cold or temperate), as well as of the concentrations applied.