Investigating lead stress on some morphological and anatomical characteristics of (Calendula officinalis)

Lead is a heavy metal and an environmental pollutant that affects the structure and performance of plants. The purpose of this research is to study the effect of lead on some morphological and anatomical features of Calendula officinalis, as ornamental plants are particularly important in terms of preventing pollutants from entering the food chain. For this purpose, an experiment was conducted with a completely random design and with three repetitions and applying treatments at the stage of 3-4 leaves. The treatments included control, lead with a low concentration of 2 mmol and high concentration of 3.5 mmol of lead. After about a month of plants planting, foliar spraying was done for a month with an interval of three days. The results of the research showed that plant length, root length and leaf length showed a significant difference with the application of lead heavy metal compared to the control. In stress, the leaf became smaller and the mesophyll parenchyma cells became less and thicker. The germination percentage of the seeds also showed a significant decrease compared to the control. Anatomical study of the stem also showed that while the diameter of the stem decreased, the number of vascular vessels decreased in severe stress, but they became larger in size. Although lead poisoning had some effects on the mentioned parameters in seedlings, these seedlings tolerated the effects of poisoning and were able to tolerate 2 mM concentration of lead.