Improving growth and physiological indices of cumin )Cuminum Cuminum L. ( by different growing substrates under stress heavy metals in the reproductive stage

Heavy metal contamination in the soil is a widespread global problem, and to reduce the accumulation and negative effects of heavy metals in plants, using different growing substrates is an effective and economical solution. In order to investigate the improvement of the growth and physiological characteristics of cumin with different growing substrates under the stress of heavy metals, a factorial experiment was carried out in the form of a completely randomized design with three replications in 2020–2021. The first factor includes four levels of heavy metals (control, cadmium, lead, and nickel) with a concentration of 50 mg/kg of soil, and the second factor includes different growing substrates at four levels (control, animal manure, compost and vermicompost). The results showed that heavy metals in the soil caused absorption and transfer to aerial organs. On the other hand, the use of organic fertilizer treatments caused a significant reduction of cadmium, lead and nickel in aerial parts compared to control. Heavy metals decreased shoot dry weight and seed yield by increasing ion leakage and decreasing the content of photosynthetic pigments. Animal manure and vermicompost significantly increased the chlorophyll content and the relative water content of leaves compared to the absence of organic fertilizers. Also, the enzyme catalase and ascorbate peroxidase of cumin leaves showed an increasing trend with the use of heavy metals. In total, the results of this research showed that the application of vermicompost and animal manure provides the best conditions for the growth of cumin under the stress of heavy metals.