Investigation of growth and yield of pot marigold (Calendula officinalis L.) under arbuscular mycorrhizal fungi symbiosis and heavy metal stress conditions

In order to study the effects of heavy metals stress and arbuscular mycorrhizal fungi (AMF) symbiosis on the growth and yield of pot marigold (Calendula officinalis L.) as a medicinal plant، a factorial experiment based on randomized complete block design with four replications was conducted at Research Greenhouse of Horticultural Sciences، College of Agriculture and Natural Resources، University of Tehran، in year of 2012. Experimental factors were two levels of mycorrhizal application (inoculated and non-inoculated with AMF) and five levels of heavy metals [0 (control)، 150 and 300 mg Pb، 40 and 80 mg Cd per kg of soil. Criteria such as time of early blooming and early flowering (days after transplanting)، herbal fresh and dry weight، plant height، number of lateral branches and total leaves per plant، leaf area، crown diameter، flower number per plant، flower diameter and flower fresh and dry weight were evaluated. The results showed that all the measured parameters improved in mycorrhizal plants compared to non-inoculated plants. Increasing heavy metal concentration had an adverse effect on all the measured criteria and only the plant height increased with an increase in Pb concentration; but this was not statistically significant. Application of Cd (80 mg per kg soil) showed a significantly negative effect on vegetative and generative growth of pot marigold and caused the lowest values of all the parameters in non-mycorrhizal plants. Additionally، using 80 mg/kg Cd، completely inhibited the generative growth in the non-mycorrhizal plants In conclusion، mycorrhizal inoculation of plants with no heavy metal pollution caused an improvement in growth and yield of C. officinalis.