The effect of cadmium stress on seeds germination characteristics of some medicinal plants under in vitro conditions

Planting date of most annual medicinal species is associated with severe irrigation competition of winter and spring crops. This competition reduces the volume of river water in downstream and consequently the concentration of heavy metals caused by industrial and municipal wastewater is increased in the river. Therefore, in order to investigate the tolerance of some spring medicinal plants to the cadmium stress of irrigation water, a factorial experiment was performed in a completely randomized design with four replications. Treatments consisted of six medicinal plants (Portulaca oleracea L., Nigella sativa, Trigonella foenum, Anethum graveolens, Carum copticum and Ocimum basilicum) and cadmium at six levels (5, 10, 15, 20, 25 and 30 mg) plus control (no cadmium). The results showed that although low concentrations of cadmium in some plants stimulated the growth of seedlings, a concentration of 30 milligrams per liter in all plants reduced the radicle and plumule length and radicle and plumule weight as well as seed vigor index. Germination percentage and rate were not substantially affected by cadmium. In this regard, fenugreek, black cumin, and dill showed the most sensitivity to cadmium toxicity. In fenugreek and ajowan plants, the plumule length was more affected by cadmium and plumule length was determined as a sensitivity index. However, for dill, purslane, basil, and black cumin plants, the radicle length was more affected and it was determine as a sensitivity index. Overall, in terms of root length, dill and basil were identified as the most sensitive and the most tolerant species to the cadmium toxicity, respectively.